Topic 3 The Chemistry of Life - Cardinal Newman High School · 2010-08-26 · Outline the role of...
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Topic 3: The chemistry of life
Transcript of Topic 3 The Chemistry of Life - Cardinal Newman High School · 2010-08-26 · Outline the role of...
Topic 3: The chemistry of life
Topic 3: The chemistry of life
3.1 Chemical elements and water
Assessment statement IBO Notes Student Notes
3.1.1
State that the most frequently occurring chemical elements in living things are carbon, hydrogen, oxygen and nitrogen.
3.1.2
State that a variety of other elements are needed by living organisms, including sulfur, calcium, phosphorus, iron and sodium.
3.1.3 State one role for each of the elements mentioned in 3.1.2.
Refer to the roles in plants, animals and prokaryotes.
3.1.4
Draw and label a diagram showing the structure of water molecules to show their polarity and hydrogen bond formation.
3.1.5 Outline the thermal, cohesive and solvent properties of water.
Aim 7: Data logging could be carried out to compare the thermal properties of water with those of other liquids.
TOK: Claims about the “memory of water” have been categorized as pseudoscientific. By what criteria can a claim be judged to be pseudoscientific?
3.1.6
Explain the relationship between the properties of water and its uses in living organisms as a coolant, medium for metabolic reactions and transport medium.
Limit the properties to those outlined in 3.1.5.
1. Many elements are necessary to form biochemicals required by living organisms. For eachelement below, state the name of one molecule containing the element and state the function ofthe molecule.
(a) Iron: Molecule.....................................................................................
Function......................................................................................
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(b) Phosphorus: Molecule.....................................................................................
Function......................................................................................
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(Total 4 marks)
2. State one function for each of the main four elements in organisms.(Total 4 marks)
3. Living organisms produce a wide variety of organic compounds.
(a) Define the term organic.
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Organic compounds are made of chemical elements, which are therefore essential to livingorganisms.
(b) State the three most commonly occurring elements.
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(c) Some organic compounds contain other elements. State one substance, or group ofsubstances, that contains
(i) nitrogen.
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(ii) phosphorus.
.....................................................................................................................................(1)
(Total 4 marks)
4. Describe the significance of water to living organisms.(Total 6 marks)
5. Explain, with reference to its properties, the significance of water as a coolant, a means oftransport and as a habitat.
(Total 8 marks)
6. Outline the significance to organisms of the different properties of water.(Total 5 marks)
3.2 Carbohydrates, lipids and proteins
Assessment statement IBO NOTES Student Notes
3.2.1 Distinguish between organic and inorganic compounds.
Compounds containing carbon that are found in living organisms (except hydrogencarbonates, carbonates and oxides of carbon) are regarded as organic.
3.2.2 Identify amino acids, glucose, ribose and fatty acids from diagrams showing their structure.
Specific names of amino acids and fatty acids are not expected.
3.2.3 List three examples each of monosaccharides, disaccharides and polysaccharides.
The examples used should be:
• glucose, galactose and fructose • maltose, lactose and sucrose • starch, glycogen and cellulose.
3.2.4
State one function of glucose, lactose and glycogen in animals, and of fructose, sucrose and cellulose in plants.
3.2.5
Outline the role of condensation and hydrolysis in the relationships between monosaccharides, disaccharides and polysaccharides; between fatty acids, glycerol and triglycerides; and between amino acids and polypeptides.
This can be dealt with using equations with words or chemical formulas.
3.2.6 State three functions of lipids. Include energy storage and thermal insulation.
3.2.7 Compare the use of carbohydrates and lipids in energy storage.
1. The diagrams below show various molecular structures.
CH C
C
C
CC
C
H
HH
H
H
HH
N C
R
C
O
OH
H
CH OH
C
H
HOH C
C
OH
H
C
H
OH
C
H
OH
OO
O
OH
OH
OH
OH
OH
(CH )3 2
2
n
I.
III.
II.
IV.2
(a) Identify which of the diagrams represent
(i) the structure of glucose.
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(ii) the structure of amino acids.
.....................................................................................................................................(1)
(iii) the structure of fatty acids.
.....................................................................................................................................(1)
(b) Discuss which of the molecules are most similar in structure.
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(Total 6 marks)
2. Describe the use of carbohydrates and lipids for energy storage in animals.(Total 5 marks)
3. Which molecule represents ribose?
CH OH
C
C
C
C
C C
C
O
O
O
O
NC C
H
H H H
H
HHH
H
H H
H
C C
OH OH
OH
OHOH
HOH C
H OH
OH
OH
OH
H C
H C
HC
OH H
A.
C. D.
B.2
2 2
2
(1)
4. Outline how monosaccharides are converted into polysaccharides.
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5. Outline the use of carbohydrates and lipids in energy storage.(Total 5 marks)
6. Lipids are essential nutrients that must be included in the diet.
(a) State one food rich in lipids suitable for a vegan diet.
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(b) Outline two functions of lipids in the body.
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(c) Discuss the possible health problems associated with diets rich in lipids.
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(Total 7 marks)
7. Draw the structure of a fatty acid.
(Total 1 mark)
8. Outline the production of a dipeptide by a condensation reaction. Include the structure of ageneralized dipeptide in your answer.
(Total 5 marks)
9. List four functions of proteins, giving an example of each.(Total 4 marks)
10. Outline the role of condensation and hydrolysis in the relationship between amino acids anddipeptides.
(Total 4 marks)
11. The complex structure of proteins can be explained in terms of four levels of structure, primary,secondary, tertiary and quaternary.
(a) Primary structure involves the sequence of amino acids that are bonded together to form apolypeptide. State the name of the linkage that bonds the amino acids together.
...............................................................................................................................................(1)
(b) Beta pleated sheets are an example of secondary structure. State one other example.
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(c) Tertiary structure in globular proteins involves the folding of polypeptides. State onetype of bond that stabilizes the tertiary structure.
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(d) Outline the quaternary structure of proteins.
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(Total 5 marks)
12. Which of the following reactions occurs when a dipeptide is formed from amino acids?
A. Hydrolysis
B. Denaturation
C. Condensation
D. Oxidation(1)
13. List the functions of membrane proteins.(Total 4 marks)
14. (a) State one named example of a fibrous protein and one named example of a globularprotein.
Fibrous: ........................................... Globular: ...........................................(2)
(b) Outline the effect of enzymes on the reactions they catalyse.
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(c) The rate of cellular respiration is controlled by the allosteric inhibition ofphosphofructokinase by ATP. Phosphofructokinase is the first enzyme in the respirationpathway. Explain the meaning of allosteric inhibition using this example.
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(Total 8 marks)
15. Which is not a primary function of protein molecules?
A. Hormones
B. Energy storage
C. Transport
D. Structure(1)
16. (a) Explain the significance of secondary structure to the structure of a protein.
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(b) State the name of a competitive enzyme inhibitor.
...............................................................................................................................................(1)
(c) Outline the difference between competitive and non-competitive enzyme inhibitors.
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(Total 6 marks)
17. Distinguish between fibrous and globular proteins, giving one example of each.(Total 5 marks)
18. (a) State two functions of proteins with a named example of each.
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(b) Explain chemiosmosis as it occurs during cell respiration.
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(Total 4 marks)
19. Which structure represents an amino acid?
H
H
H
H
H
H
H
H
H
OH
OH
H
H
H
H
H
H
H
SH
OH
N
N
N
N
C
C
C
C
C
C
C
C
O
O
O
O
A.
C.
B.
D.
(1)
20. The diagram below shows a channel protein in a membrane. Which parts of the surface of theprotein would be composed of polar amino acids.
A. I and II only
B. II and III only
C. III and IV only
D. I and IV only(1)
21. (a) State two products of the process of glycolysis.
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(b) Explain the significance of polar and non-polar amino acids within the cell.
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(Total 4 marks)
22. (a) State one type of secondary structure of a protein.
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(b) Outline the differences between globular and fibrous proteins, giving a named example ofeach.
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(c) Explain the significance of polar amino acids for membrane proteins.
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(Total 6 marks)
23. Draw the basic structure of an amino acid, and label the groups that are used in peptide bondformation.
(Total 4 marks)
3.3 DNA structure
Assessment statement Teacher’s notes Student Notes
3.3.1 Outline DNA nucleotide structure in terms of sugar (deoxyribose), base and phosphate.
Chemical formulas and the purine/pyrimidine subdivision are not required. Simple shapes can be used to represent the component parts. Only the relative positions are required.
3.3.2 State the names of the four bases in DNA.
3.3.3 Outline how DNA nucleotides are linked together by covalent bonds into a single strand.
Only the relative positions are required.
3.3.4 Explain how a DNA double helix is formed using complementary base pairing and hydrogen bonds.
3.3.5 Draw and label a simple diagram of the molecular structure of DNA.
An extension of the diagram in 3.3.3 is sufficient to show the complementary base pairs of A–T and G–C, held together by hydrogen bonds and the sugar–phosphate backbones. The number of hydrogen bonds between pairs and details of purine/pyrimidines are not required.
TOK: The story of the elucidation of the structure of DNA illustrates that cooperation and collaboration among scientists exists alongside competition between research groups. To what extent was Watson and Crick’s “discovery” of the three‐dimensional structure of DNA dependent on the use of data generated by Rosalind Franklin, which was shared without her knowledge or consent?
1. Draw a diagram of the molecular structure of a portion of DNA.(Total 4 marks)
2. Draw a diagram showing the molecular structure of a section of the DNA molecule.(Total 5 marks)
3. What is the composition of the backbone of DNA?
A. Alternating sugar and phosphate molecules
B. Complementary base pairs
C. Alternating sugar and base molecules
D. A polysaccharide(1)
4. Which of the following are connected by a hydrogen bond?
A. The hydrogen and oxygen atoms of a water molecule
B. A base pair of a DNA molecule
C. Two amino acid molecules of a dipeptide
D. Two glucose molecules in a disaccharide(1)
5. The structure of the DNA double helix was described by Watson and Crick in 1953. Explain thestructure of the DNA double helix, including its subunits and the way in which they are bondedtogether.
(Total 8 marks)
6. Distinguish between the structure of DNA and RNA.
DNA RNA
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(Total 3 marks)
7. To which parts of the deoxyribose molecule do phosphates bind in DNA?
CH OH
IVH H
H
H
H OH
OH
II
III
I2
O
V
A. I and V
B. III and IV
C. II and III
D. III and V(1)
3.4 DNA replication
Assessment statement Teacher’s Notes Student Notes
3.4.1
Explain DNA replication in terms of unwinding the double helix and separation of the strands by helicase, followed by formation of the new complementary strands by DNA polymerase.
It is not necessary to mention that there is more than one DNA polymerase.
3.4.2
Explain the significance of complementary base pairing in the conservation of the base sequence of DNA.
3.4.3 State that DNA replication is semi‐conservative.
3.5 Transcription and translation
Assessment statement Teacher’s notes Student Notes
3.5.1 Compare the structure of RNA and DNA.
Limit this to the names of sugars, bases and the number of strands.
3.5.2
Outline DNA transcription in terms of the formation of an RNA strand complementary to the DNA strand by RNA polymerase.
3.5.3 Describe the genetic code in terms of codons composed of triplets of bases.
3.5.4 Explain the process of translation, leading to polypeptide formation.
Include the roles of messenger RNA (mRNA), transfer RNA (tRNA), codons, anticodons, ribosomes and amino acids.
3.5.5 Discuss the relationship between one gene and one polypeptide.
Originally, it was assumed that one gene would invariably code for one polypeptide, but many exceptions have been discovered.
TOK: The way in which theories are modified as related evidence accumulates could be discussed, and whether contrary evidence should cause a theory to be discarded immediately if there are exceptions to it. Where a theory is suddenly and totally abandoned, to be replaced by a different theory, this is known as a paradigm shift.
1. What is the function of helicase?
A. It forms bonds between DNA nucleotides.
B. It adds new nucleotides to the DNA helix.
C. It forms the DNA helix.
D. It separates DNA strands.(1)
2. Which enzyme removes the RNA primer during replication?
A. RNA primase
B. DNA polymerase I
C. DNA ligase
D. Helicase(1)
3. State a role for each of four different named enzymes in DNA replication.(Total 6 marks)
4. The diagram below shows a short section of DNA molecule before and after replication. If thenucleotides used to replicate the DNA were radioactive, which strands in the replicatedmolecules would be radioactive?
G C T A C
G C T A C
G C T A C
C G A T G
C G A T G
C G A T G
I
II
III
IV
A. II and III only
B. I and III only
C. I and II only
D. I, II, III and IV(1)
5. Living organisms use DNA as their genetic material. Explain how DNA is replicated within thecells of living organisms.
(Total 8 marks)
6. A biochemist isolated and purified molecules needed for DNA replication. When some DNAwas added replication occurred, but the DNA molecules formed were defective. Each consistedof a normal DNA strand paired with segments of DNA a few hundred nucleotides long. Whichof the following had been left out of the mixture?
A. DNA ligase
B. Helicase
C. Nucleotides
D. DNA polymerase(1)
1. Describe the consequence of a base substitution mutation with regards to sickle cell anaemia.(Total 7 marks)
2. The following diagram shows the lac operon which helps to regulate the expression of genes.
DNA
lac I lac Z lac Y lac APromoter Operator
-galactosidase
Permease
Acetylase
[Source: Riki Lewis, Human Genetics, 3rd Edition, William C Brown, (1999), page 158]
(a) Outline the term operon.
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(b) Outline the relationship between the lac operon and transcription.
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(Total 5 marks)
3. Explain the process of translation.(Total 9 marks)
4. What is removed to form mature eukaryotic mRNA?
A. RNA primers
B. Exons
C. RNA polymerases
D. Introns(1)
5. Outline the process of translation.(Total 5 marks)
6. A certain gene codes for a polypeptide that is 120 amino acids long. Approximately how manynucleotides long is the mRNA that codes for this polypeptide likely to be?
A. 30
B. 40
C. 360
D. 480(1)
7. Sickle cell anemia is a serious disease caused by a single base substitution mutation. Explainhow a single base substitution mutation can have significant consequences for an individual.
(Total 6 marks)
8. Compare DNA transcription with translation.(Total 4 marks)
9. (a) Define the term degenerate as it relates to the genetic code.
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(b) Apart from international cooperation, outline two positive outcomes of the HumanGenome Project.
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(c) State the catalytic activity of reverse transcriptase.
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(d) State one use of monoclonal antibodies in diagnosis and one use in treatment.
Diagnosis: ........................................................................................................................
Treatment: ........................................................................................................................(2)
(Total 6 marks)
10. Distinguish between the structure of DNA and RNA.
DNA RNA
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(Total 3 marks)
11. It had always been assumed that eukaryotic genes were similar in organization to prokaryoticgenes. However, modern techniques of molecular analysis indicated that there are additionalDNA sequences that lie within the coding region of genes. Exons are the DNA sequences thatcode for proteins while introns are the intervening sequences that have to be removed. Thegraph shows the number of exons found in genes for three different groups of eukaryotes.
Percentage of genes
Saccharomyces cerevisiae (a yeast)
Drosophila melanogaster (fruit fly)
Mammals
100
80
60
40
20
040
30
20
10
020
15
10
5
01 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 <30<40<60>60
Number of exons
[Source: Benjamin Lewin, (1999) Genes VII, OUP, page 55]
(a) Calculate the percentage of genes that have five or less exons in mammals.
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(b) Describe the distribution of the number of exons and the percentage of genes inD. melanogaster.
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(c) (i) Compare the distributions of the number of exons found in genes of S. cerevisiaeand mammals.
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(ii) Suggest one reason for the differences in the numbers of exons found in genes of S. cerevisiae and mammals.
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Human DNA has been analysed and details of certain genes are shown in the table below.
Gene Gene size / kb* mRNA size / kb Number ofintrons
Insulin 1.7 0.4 2
Collagen 38.0 5.0 50
Albumin 25.0 2.1 14
Phenylalanine hydroxylase 90.0 2.4 12
Dystrophin 2 000.0 17.0 50
*kilobase pairs
[Source: William S Klug and Michael R Cummings, (2002), Concepts of Genetics, 7th edition, Prentice Hall, page 314]
(d) Calculate the average size of the introns for the albumin gene.
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(e) Analyse the relationship between gene size and the number of introns.
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(f) Determine the maximum number of amino acids that could be produced by translating thephenylalanine hydroxylase mRNA.
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Hemoglobin is a protein composed of two pairs of globin molecules. During the process ofdevelopment from conception to adulthood, human hemoglobin changes in composition. Adulthemoglobin consists of two alpha- and two beta-globin molecules. Two globin genes occur onchromosome 16: alpha- and zeta-globin. Four other globin genes are found on chromosome 11:beta, delta, epsilon and gamma. The graph below illustrates the changes in expression of theglobin genes over time.
50
40
30
20
10
0 10 20 30 40 2 4 6weeks of gestation birth month of age
Percentage ofhemoglobin
alpha-globingamma-globinbeta-globindelta-globinepsilon-globinzeta-globin
Key:
[Source: adapted from M Cummings, Human Heredity, 4th edition, West/Wadsworth Publishing Company]
(g) State which globin genes are the first to be expressed after fertilization.
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(h) Compare the expression of the gamma-globin gene with the beta-globin gene.
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(i) Deduce the composition of the hemoglobin molecules
at 10 weeks of gestation. ...................................................................................................
...................................................................................................
2 months after birth. ...................................................................................................
...................................................................................................(2)
(Total 17 marks)
12. Describe the genetic code.(Total 6 marks)
13. Where do transcription and translation occur in eukaryotic cells?
Transcription Translation
A. Cytoplasm Cytoplasm
B. Cytoplasm Mitochondria
C. Nucleus Cytoplasm
D. Nucleus Nucleus(1)
14. The lac operon model of gene control in the bacterium Escherichia coli explains how theproduction of the enzyme β-galactosidase is controlled. Which conditions are necessary forβ-galactosidase enzyme to be produced in this bacterium?
A. Glucose is present and lactose is absent
B. Glucose and lactose are present
C. Glucose is absent and lactose is present
D. Glucose and lactose are both absent(1)
15. The process of translation involves the use of transfer RNA (tRNA) and amino acids. Outlinethe structure of tRNA.
(Total 5 marks)
16. Explain the process of translation.(Total 9 marks)
3.6 Enzymes
Assessment statement Teacher’s notes Student Notes
3.6.1 Define enzyme and active site.
3.6.2 Explain enzyme–substrate specificity.
The lock‐and‐key model can be used as a basis for the explanation. Refer to the three‐dimensional structure. The induced‐fit model is not expected at SL.
3.6.3 Explain the effects of temperature, pH and substrate concentration on enzyme activity.
Aim 7: Enzyme activity could be measured using data loggers such as pressure sensors, pH sensors or colorimeters.
Aim 8: The effects of environmental acid rain could be discussed.
3.6.4 Define denaturation.
Denaturation is a structural change in a protein that results in the loss (usually permanent) of its biological properties. Refer only to heat and pH as agents.
3.6.5 Explain the use of lactase in the production of lactose‐free milk.
Aim 8: Production of lactose‐free milk is an example of an industrial process depending on biological methods (biotechnology). These methods are of huge and increasing economic importance.
Int/TOK: Development of some techniques benefits particular human populations and not others because of the natural variation in human characteristics. Lactose intolerance is found in a high proportion of the human population (for example, in Asia) but more rarely among those of European origin. Sometimes a transfer of biotechnology is needed when techniques are developed in one part of the world that are more applicable in another.
1. (a) Define the term active site of an enzyme.
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(b) Outline how enzymes catalyze biochemical reactions.
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(c) Explain the effect of pH on enzyme activity.
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(d) State three functions of lipids.
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(Total 8 marks)
2. Explain the effects of temperature, pH and substrate concentration on enzyme activity.(Total 8 marks)
3. Consider the metabolic pathway shown below.
A B C D E1 2 3 4
If there is end-product inhibition, which product (B to E) would inhibit which enzyme (1 to 4)?
Product Enzyme
A. C 4
B. B 3
C. B 4
D. E 1(1)
4. Alcohol dehydrogenase is an enzyme that catalyses the reversible reaction of ethanol andethanal according to the equation below.
NAD+CH3CH2OH CH3CHO+NADH+H+
ethanol ethanal
The initial rate of reaction can be measured according to the time taken for NADH to beproduced.
In an experiment, the initial rate at different concentrations of ethanol was recorded (noinhibition). The experiment was then repeated with the addition ofl mmol dm-3 2,2,2-trifluoroethanol, a competitive inhibitor of the enzyme. A third experimentusing a greater concentration of the same inhibitor (3 mmol dm-3) was performed. The resultsfor each experiment are shown in the graph below.
1.21.11.00.90.80.70.60.50.40.30.20.10.0
0 10 20 30 40 50 60 70 80 90 100Ethanol concentration / mmol dm–3
Initial rate of reaction/ arbitrary units
–3
–3
no inhibition1 mmol dm inhibitor3 mmol dm inhibitor
[Source: R Taber, Biochemical Education, (1998) 26, pages 239-242]
(a) Outline the effect of increasing the substrate concentration on the control reaction (noinhibition).
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(b) (i) State the initial rate of reaction at an ethanol concentration of 50 mmol dm–3
in the presence of the inhibitor at the following concentrations.
1 mmol dm–3: ...................................................................................................
3 mmol dm–3: ...................................................................................................(1)
(ii) State the effect of increasing the concentration of inhibitor on the initial rate ofreaction.
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(c) Explain how a competitive inhibitor works.
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(Total 7 marks)
5. What can reduce the effect of a competitive inhibitor of an enzyme?
A. Decrease the temperature at which the reaction takes place.
B. Increase the temperature at which the reaction takes place.
C. Increase the substrate concentration.
D. Add a non-competitive inhibitor.(1)
6. Outline enzyme-substrate specificity.(Total 5 marks)
7. Explain how allosteric control of metabolic pathways by end-product inhibition includesnegative feedback and non-competitive inhibition.
(Total 8 marks)
8. Explain the effect of substrate concentration on enzyme activity.
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................(Total 3 marks)
9. What is the advantage of using pectinase in fruit juice production?
A. The pectin content of the fruit is increased, making the nutritional value of the juice higher.
B. The pectin content of the fruit is reduced, making the energy content of the juice lower.
C. The pectin content of the fruit is reduced, making the juice easier to extract.
D. The pectin content of the fruit is increased, giving the juice a thicker texture.(1)
10. What effect do enzymes have on the activation energy of exergonic and endergonic reactions?
Activation energy ofexergonic reactions
Activation energy ofendergonic reactions
A. increases increases
B. decreases decreases
C. increases decreases
D. decreases increases(1)
11. Outline two examples of the commercial application of enzymes in biotechnology.(Total 6 marks)
12. The enzyme aspartate carbomyltransferase (ACTase) is a key regulatory enzyme in nucleotidemetabolism in bacteria. The activity of this enzyme was studied in the bacterium Helicobacterpylori, an important human pathogen. ACTase activity and the growth of H. pylori weremeasured at different concentrations of carbomoyl aspartate (CAA), the end product of thereaction catalysed by ACTase.
Key: ACTase activity growthH. pylori
100
75
50
25
0
100
75
50
25
00 10 20 30 40 50 60
Concentration of carbamoyl aspartate / mmol dm–3
ACTase activity /% of control
Growth /% of control
[Source: Burns, et al., Biological Procedures Online, (1998), www.biologicalprocedures.com]
(a) (i) State the growth of H. pylori at a CAA concentration of 30 mmol dm–3.
.....................................................................................................................................(1)
(ii) Calculate the change in ACTase activity between CAA concentrations of 20 and 40mmol dm–3.
.....................................................................................................................................
.....................................................................................................................................(1)
(b) Compare the effect of increasing CAA concentration on the growth of H. pylori andACTase activity.
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................(2)
(c) Explain the effect of CAA on ACTase activity.
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................(2)
(d) Suggest a direct medical application of this information.
...............................................................................................................................................
...............................................................................................................................................(1)
(Total 7 marks)
13. Which of the following could cause denaturation of an enzyme?
A. Substrate concentration
B. A competitive inhibitor
C. High temperature
D. Low salt concentration(1)
14. The graph below shows the effect of changing the substrate concentration on an enzymecontrolled reaction.
40 % substrate20 % substrate
10 % substrate
5 % substrate
2.5 % substrate
0 % substrateTime
Amount of product formed
What is the correct interpretation of these data?
A. The rate of reaction increases continuously with increase in substrate concentration.
B. The rate of reaction decreases continuously with increase in substrate concentration.
C. The rate of reaction increases up to a point and then remains constant.
D. The rate of reaction is not affected by any change in the substrate concentration.(1)
15. How does the enzyme pectinase help in fruit juice production?
A. Pectinase increases the amount of protein in the juice extracted.
B. Pectinase decreases the lipid content of the juice extracted.
C. Pectinase increases the volume of the juice extracted.
D. Pectinase eliminates toxins from the juice extracted.(1)
16. In the enzyme controlled pathway shown below, which compound is most likely to inhibitenzyme (w)?
IVIIIIIIPrecursor
enzymeenzymeenzymeenzyme
→→→→zyxw
A. I
B. II
C. III
D. IV (1)
17. (a) Describe the role of skin arterioles in the regulation of body temperature.
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................(3)
(b) Explain how temperature affects the rate of transpiration from a typical mesophytic plant.
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................(3)
(c) Explain the role of temperature on enzyme activity.
...............................................................................................................................................
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...............................................................................................................................................
...............................................................................................................................................
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...............................................................................................................................................(3)
(Total 9 marks)
18. Outline two examples of the commercial application of named enzymes in biotechnology.(Total 6 marks)
19. Explain competitive and non-competitive inhibition, including allostery.(Total 8 marks)
3.7 Cell respiration
Assessment statement Teacher’s notes Student Notes
3.7.1 Define cell respiration. Cell respiration is the controlled release of energy from organic compounds in cells to form ATP.
3.7.2
State that, in cell respiration, glucose in the cytoplasm is broken down by glycolysis into pyruvate, with a small yield of ATP.
3.7.3
Explain that, during anaerobic cell respiration, pyruvate can be converted in the cytoplasm into lactate, or ethanol and carbon dioxide, with no further yield of ATP.
Mention that ethanol and carbon dioxide are produced in yeast, whereas lactate is produced in humans.
Aim 7: Data logging using gas sensors, oxygen, carbon dioxide or pH probes could be used.
3.7.4
Explain that, during aerobic cell respiration, pyruvate can be broken down in the mitochondrion into carbon dioxide and water with a large yield of ATP.
1. The diagram below shows possible pathways for the breakdown of glucose in various cells.
Glucose
A
Process Q Process R(no oxygen present) (oxygen present)
B C + D D + E
(a) State the names of processes Q and R.
Q: ..................................................................................................................................(1)
R: ..................................................................................................................................(1)
(b) Deduce the names of substances A and D.
A: ..................................................................................................................................(1)
D: ..................................................................................................................................(1)
(c) State the organelle in which process R takes place.
...............................................................................................................................................(1)
(Total 5 marks)
2. At the start of glycolysis, glucose is phosphorylated to produce glucose 6-phosphate, which isconverted into fructose 6-phosphate. A second phosphorylation reaction is then carried out, inwhich fructose 6-phosphate is converted into fructose 1,6-bisphosphate. This reaction iscatalyzed by the enzyme phosphofructokinase. Biochemists measured the enzyme activity ofphosphofructokinase (the rate at which it catalyzed the reaction) at different concentrations offructose 6-phosphate. The enzyme activity was measured with a low concentration of ATP and ahigh concentration of ATP in the reaction mixture. The graph below shows the results.
Low ATP concentration
High ATP concentration
Enzyme activity
Fructose 6-phosphate concentration
(a) (i) Using only the data in the above graph, outline the effect of increasing fructose6-phosphate concentration on the activity of phosphofructokinase, at a low ATPconcentration.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(2)
(ii) Explain how increases in fructose 6-phosphate concentration affect the activity ofthe enzyme.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(2)
(b) (i) Outline the effect of increasing the ATP concentration on the activity ofphosphofructokinase.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(2)
(ii) Suggest an advantage to living organisms of the effect of ATP onphosphofructokinase.
.....................................................................................................................................
.....................................................................................................................................(1)
(Total 7 marks)
3. Explain the process of aerobic respiration including oxidative phosphorylation.(Total 8 marks)
4. (a) Define the term species.
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................(2)
(b) List three kingdoms into which living organisms are classified.
...............................................................................................................................................
...............................................................................................................................................(1)
(c) The seven levels used in hierarchy of taxa are:
Kingdom, Phylum, Class, Order, Family, Genus and Species.
State which two are used in the binomial system of nomenclature.
...............................................................................................................................................(1)
(Total 4 marks)
5. Of the following products, which is produced by both anaerobic respiration and aerobicrespiration in humans?
I. Pyruvate
II. ATP
III. Lactate
A. I only
B. I and II only
C. I, II and III
D. II and III only(1)
6. Which is not a product of the Krebs cycle?
A. CO2
B. NADH + H+
C. Pyruvate
D. ATP(1)
7. How many ATP molecules (net yield) are produced per molecule of glucose as a direct result ofglycolysis?
A. 2
B. 4
C. 10
D. 38(1)
8. What happens during muscle contraction?
A. Both actin and myosin filaments shorten.
B. Na+ ions are taken up by the sarcoplasmic reticulum.
C. The actin and myosin filaments slide over each other.
D. Cross bridges remain attached to the filaments.(1)
9. Explain the similarities and differences in anaerobic and aerobic cellular respiration.(Total 8 marks)
10. Anaerobic respiration occurs in the absence of oxygen while aerobic respiration requiresoxygen.
(a) State one final product of anaerobic respiration.
...............................................................................................................................................(1)
(b) Complete the table showing the differences between oxidation and reduction.
Oxidation Reduction
Electrons gained orlost
Oxygen or hydrogengained or lost
(2)
(c) The structure of a mitochondrion is shown in the electron micrograph below.
Name the parts labelled A, B and C and state the function of each.
Part A: Name: ..................................................................................................................
Function: .............................................................................................................
Part B: Name: ..................................................................................................................
Function: .............................................................................................................
Part C: Name: ..................................................................................................................
Function: .............................................................................................................(3)
(Total 6 marks)
11. The rate of carbon dioxide uptake by the green succulent shrub Aeonium goochiae can indicatethe amount of photosynthesis taking place in the plant. This rate was measured at 15°C and30°C over a 24-hour period. The units of carbon dioxide absorption are mg CO2 h–1.
The results are shown below. The centre of the graph corresponds to –2 mg CO2 h–1 and theouter ring is +2.5mg CO2 h–1.
Key:30ºC15ºC2400 (midnight)
23002200
2100 (late evening)
2000
1900
1800 (evening)
1700
1600
1500 (early afternoon)
14001300
1200 (mid-day)1100
1000
0900 (late morning)
0800
0700
0600 (morning)
0500
0400
0300 (early morning)
020001002.5
21.5
10.5
0–0.5
–1–1.5
–2
[Source: adapted from www.biologie.uni-hamburg.de/b-online/e24/9.htm]
(a) Identify a time that carbon dioxide uptake was the same at both temperatures.
...............................................................................................................................................(1)
(b) State the maximum rate of carbon dioxide uptake at 15°C.
...............................................................................................................................................(1)
(c) Compare the rate of carbon dioxide uptake at each temperature in daylight and darkness.
...............................................................................................................................................
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...............................................................................................................................................(3)
(d) Suggest why the carbon dioxide uptake may at times be negative.
...............................................................................................................................................
...............................................................................................................................................(1)
(Total 6 marks)
12. (a) (i) Identify the cell organelle shown in the micrograph below.
.....................................................................................................................................(1)
(ii) Identify the structure labelled I above and explain how it is adapted for theorganelle to function efficiently.
.....................................................................................................................................
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.....................................................................................................................................(3)
(b) Describe the role of acetyl CoA in the metabolism of lipids.
...............................................................................................................................................
...............................................................................................................................................
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(Total 6 marks)
13. Which way do the protons flow when ATP is synthesized in mitochondria?
A. From the inner matrix to the intermembrane space
B. From the intermembrane space to the inner matrix
C. From the intermembrane space to the cytoplasm
D. From the cytoplasm to the intermembrane space(1)
14. What accumulates in the inter-membrane space of the mitochondrion during electron transport?
A. ATP
B. Electrons
C. Protons (hydrogen ions)
D. Oxygen(1)
15. Biosphere 2, an enormous greenhouse built in the Arizona desert in the USA, has been used tostudy five different ecosystems. It is a closed system so measurements can be made undercontrolled conditions. The effects of different factors, including changes in carbon dioxideconcentration in the greenhouse, were studied. The data shown below were collected over thecourse of one day in January 1996.
1200
1000
800
600
400
200
0
1600
1400
1200
1000
800
600
400
200
0
CO /ppm
light /mol m sμ
2–2 –1
0 1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24Time / hours
Key: CO Light
2
[Source: http://www.Ideo.columbia.edu/martins/climate_water/labs/lab6/labinstr6/html]
(a) (i) Identify the time of day when the sun rose.
.....................................................................................................................................(1)
(ii) Identify the time of minimal CO2 concentration.
.....................................................................................................................................(1)
(b) Determine the maximum difference in the concentration of CO2 over the 24-hour period.
...............................................................................................................................................
...............................................................................................................................................(1)
(c) Suggest reasons for changes in CO2 concentration during the 24-hour period.
...............................................................................................................................................
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(Total 5 marks)
16. (a) State two functions of proteins with a named example of each.
...............................................................................................................................................
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...............................................................................................................................................(2)
(b) Explain chemiosmosis as it occurs during cell respiration.
...............................................................................................................................................
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(Total 4 marks)
17. What is the sequence of stages during the conversion of glucose into pyruvate in glycolysis?
A. lysis phosphorylation of sugar oxidation
B. lysis oxidation phosphorylation of sugar
C. phosphorylation of sugar lysis oxidation
D. phosphorylation of sugar oxidation lysis(1)
18. (a) State two products of the process of glycolysis.
...............................................................................................................................................
...............................................................................................................................................(1)
(b) Explain the significance of polar and non-polar amino acids within the cell.
...............................................................................................................................................
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(Total 4 marks)
19. The respiratory quotient (RQ) is a measure of the metabolic activity of an animal. It is the ratioof CO2 produced to O2 consumed. In general, the lower the RQ value the higher the energyyield. The RQ is dependent on the diet consumed by the animal. The following table lists thetypical RQ values for specified diets.
Diet RQ
Lipid 0.71
Carbohydrate 1.00
Protein 0.74
[Source: Walsberg and Wolf, Journal of Experimental Biology, (1995), 198, pages 213–219. Reproduced bypermission of The Company of Biologists Ltd]
In an experiment to assess RQ values for house sparrows, the birds were fed a diet of puremealworms (beetle larvae) or millet (a type of grain).
The graph below shows the RQ values of a house sparrow fed on a high carbohydrate diet(millet) and a high lipid diet (mealworms).
1.0
0.9
0.8
0.7
0.60 1 2 3 4 5 6 7
Time after feeding / h
Res
pira
tory
quo
tient
Key: Millet Mealworms
[Source: Walsberg and Wolf, Journal of Experimental Biology, (1995), 198, pages 213–219. Reproduced bypermission of The Company of Biologists Ltd]
(a) Compare the RQ values for millet and mealworms between 1 hour and 6 hours afterfeeding.
...............................................................................................................................................
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...............................................................................................................................................(2)
The expected RQ value for house sparrows metabolizing millet is 0.93. The expected valuewhen metabolizing mealworms is 0.75.
(b) Explain why the expected RQ values for millet and mealworms are different.
...............................................................................................................................................
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...............................................................................................................................................(2)
(c) Suggest reasons for
(i) the high initial RQ values for house sparrows fed on millet.
.....................................................................................................................................
.....................................................................................................................................(1)
(ii) the rapid fall in RQ values for house sparrows fed on millet.
.....................................................................................................................................
.....................................................................................................................................(1)
(Total 6 marks)
20. Which of the following produce ATP in mitochondria?
A. The movement of protons from the matrix to the intermembrane space
B. The movement of protons from the intermembrane space to the cytoplasm
C. The splitting of water molecules and the movement of electrons to oxygen
D. The movement of protons from the intermembrane space to the matrix(1)
21. How many molecules of acetyl CoA (ethanoyl CoA) does the oxidation of the fatty acid stearicacid produce?
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
COOH
3
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
Stearic acid
A. 2
B. 6
C. 9
D. 18(1)
22. Explain the process of aerobic cellular respiration.(Total 8 marks)
3.8 Photosynthesis
Assessment statement Teacher’s notes Student Notes
3.8.1 State that photosynthesis involves the conversion of light energy into chemical energy.
3.8.2 State that light from the Sun is composed of a range of wavelengths (colours).
Reference to actual wavelengths or frequencies is not expected.
3.8.3 State that chlorophyll is the main photosynthetic pigment.
3.8.4 Outline the differences in absorption of red, blue and green light by chlorophyll.
Students should appreciate that pigments absorb certain colours of light. The remaining colours of light are reflected. It is not necessary to mention wavelengths or the structure responsible for the absorption.
Aim 7: Data logging using colorimeters or light sensors could be used.
3.8.5
State that light energy is used to produce ATP, and to split water molecules (photolysis) to form oxygen and hydrogen.
3.8.6
State that ATP and hydrogen (derived from the photolysis of water) are used to fix carbon dioxide to make organic molecules.
3.8.7
Explain that the rate of photosynthesis can be measured directly by the production of oxygen or the uptake of carbon dioxide, or indirectly by an increase in biomass.
The recall of details of specific experiments to indicate that photosynthesis has occurred or to measure the rate of photosynthesis is not expected.
3.8.8
Outline the effects of temperature, light intensity and carbon dioxide concentration on the rate of photosynthesis.
The shape of the graphs is required. The concept of limiting factors is not expected.
Aim 7: Data logging using gas sensors, oxygen, carbon dioxide or pH probes could be used.
1. There are many abiotic factors that affect the rate of photosynthesis in terrestrial plants. Wheatis an important cereal crop in many parts of the world. Wheat seedlings were grown at threedifferent concentrations of carbon dioxide (in parts per million) and the rate of photosynthesiswas measured at various light intensities.
50
40
30
20
10
00 5 10 15 20
Light intensity / × 10 lumen m
2
3
2
2
2
–2
–1R
ate
of p
hoto
synt
hesi
s /
l CO
m
inμ
key:1300 ppm CO500 ppm CO280 ppm CO
[Source: Adapted from J P Kimmins, Forest Ecology, (2nd edition) page 161]
(a) Describe the relationship between the rate of photosynthesis and light intensity for wheatseedlings grown at a CO2 concentration of 500 ppm.
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(b) Outline the effect of CO2 concentration on the rate of photosynthesis of the wheatseedlings.
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(c) The normal atmospheric concentration of CO2 is 370 ppm. Deduce the effect of doublingthe CO2 concentration to 740 ppm on the growth of wheat plants.
...............................................................................................................................................
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Leaf area and chlorophyll levels were measured in sun leaves and shade leaves of Hedera helix(English Ivy) and Prunus laurocerasus (Cherry Laurel). Sun leaves developed under maximalsunlight conditions while shade leaves developed at reduced sunlight levels in the shadow ofother leaves.
Species Leaf Type Chlorophyll/μg ml-1
Leaf Area/cm2
Ivy Shade 4.3 72.6
Sun 3.8 62.9
Laurel Shade 4.7 38.7
Sun 4.2 25.7
[Source: D Curtis, Plant Ecology independent project, 1990]
(d) Calculate the percentage increase in the amount of chlorophyll in shade leaves of ivycompared to sun leaves of ivy
...............................................................................................................................................
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(e) Suggest a reason for the differences in chlorophyll concentration and leaf area in sun andshade leaves in these two species.
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(Total 10 marks)
2. Explain the reasons for
(a) a large area of thylakoid membrane in the chloroplast.
...............................................................................................................................................
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(b) low rates of photosynthesis in plants growing beneath trees, where the light has alreadypassed through the trees’ leaves.
...............................................................................................................................................
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(c) large amounts of RuBP carboxylase in the chloroplast.
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(Total 6 marks)
3. The graph below shows the variation in the concentration of atmospheric carbon dioxide since1970.
375
370
365
360
355
350
345
335
330
325
320
1970
1975
1980
1985
1990
1995
2000
COconcentration
/ ppm
2
[Source: C D Keeling and T P Whorf, Atmosphere CO2 concentrations (ppm) derived from in situ air samplescollected at Mauna Loa Observatory, Hawaii]
The annual fluctuation is mainly the result of changes in the levels of photosynthesis associatedwith the seasons in Northern Hemisphere forests.
(a) (i) Describe the overall trend shown in the graph.
.....................................................................................................................................
.....................................................................................................................................(1)
(ii) Suggest a cause for the overall trend throughout the period 1970–1999.
.....................................................................................................................................
.....................................................................................................................................(1)
(b) (i) Using a clear label, identify any one point on the graph which shows the CO2 levelin mid-summer.
(1)
(ii) Explain why the concentration of CO2 varies with the seasons.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(2)
(c) Identify one gas, other than CO2 , which is contributing to the enhanced greenhouseeffect.
...............................................................................................................................................(1)
(Total 6 marks)
4. The unicellular green alga Phaeodactylum tricornutum is photosynthetic. Cell biologistsgenetically modified this organism by adding a glucose transporter gene. The modified andunmodified algae were grown in a nutrient medium under a series of different conditions andthe growth rate of the cells was measured.
12
10
8
6
4
2
00 2 4 6 8 0 2 4 6 8
Time / days
Cell density /10 cells cm
Key:= light and no glucose in the medium
= light and glucose in the medium
= dark and glucose in the medium
Unmodified algae Modified algae
–37
[Source: L A Zaslavskaia, et al., Adapted (2001) Science, 292, pages 2073–2075]
(a) State the role of glucose in the metabolism of cells.
...............................................................................................................................................(1)
(b) Deduce where you would expect to find the glucose transporter protein in the modifiedalgae cells.
...............................................................................................................................................
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...............................................................................................................................................(2)
(c) Compare the effect of light on the modified and the unmodified cells.
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Commercially, unmodified algae are grown in shallow sunlit ponds or illuminated containers. The cells only grow in the top few centimetres. However, the modified algae can grow at anydepth.
(d) Explain why the modified algae can grow at any depth whereas the unmodified algae canonly grow at the surface.
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(Total 8 marks)
5. State two products of the light dependent reaction of photosynthesis.
...............................................................................................................................................(Total 2 marks)
6. Which two colours of light does chlorophyll absorb most?
A. Red and yellow
B. Green and blue
C. Red and green
D. Red and blue(1)
7. During photosynthesis in plants, light energy is absorbed by chlorophyll. This energy is thenused to carry out photolysis, which supply substances that are needed to convert carbon dioxideinto organic molecules such as glucose.
(a) State the names of two products of photolysis in photosynthesis.
1. ...........................................................................................................................................
2. ...........................................................................................................................................(2)
(b) Explain briefly one method for measuring the rate of photosynthesis in a plant.
...............................................................................................................................................
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(c) The rate of photosynthesis is affected by light intensity. Draw a line on the graph belowto show the relationship between light intensity and the rate of photosynthesis.
rate of photosynthesis
light intensity(2)
(d) State two factors in the environment of a plant, apart from light intensity, that can affectthe rate of photosynthesis in the plant.
1. ...........................................................................................................................................
2. ...........................................................................................................................................(2)
(Total 8 marks)
8. (a) State the main photosynthetic pigment in plants.
...............................................................................................................................................(1)
(b) State the two materials used to convert carbon dioxide to organic molecules in plants.
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(c) Explain two ways in which the rate of photosynthesis can be measured.
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(Total 7 marks)
9. (a) State the site of the light-independent reactions in photosynthesis.
...............................................................................................................................................(1)
The absorption spectrum of chlorophyll a and chlorophyll b are shown in the graph below.
Absorbance
400 500 600 700Wavelength / nm
chlorophyll b
chlorophyll a
(b) On the graph above, draw the action spectrum of photosynthesis for a green plant.(1)
(c) Explain photophosphorylation in terms of chemiosmosis.
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(Total 5 marks)
10. The rate of carbon dioxide uptake by the green succulent shrub Aeonium goochiae can indicatethe amount of photosynthesis taking place in the plant. This rate was measured at 15°C and30°C over a 24-hour period. The units of carbon dioxide absorption are mg CO2 h–1.
The results are shown below. The centre of the graph corresponds to –2 mg CO2 h–1 and theouter ring is +2.5mg CO2 h–1.
Key:30ºC15ºC2400 (midnight)
23002200
2100 (late evening)
2000
1900
1800 (evening)
1700
1600
1500 (early afternoon)
14001300
1200 (mid-day)1100
1000
0900 (late morning)
0800
0700
0600 (morning)
0500
0400
0300 (early morning)
020001002.5
21.5
10.5
0–0.5
–1–1.5
–2
[Source: adapted from www.biologie.uni-hamburg.de/b-online/e24/9.htm]
(a) Identify a time that carbon dioxide uptake was the same at both temperatures.
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(b) State the maximum rate of carbon dioxide uptake at 15°C.
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(c) Compare the rate of carbon dioxide uptake at each temperature in daylight and darkness.
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(d) Suggest why the carbon dioxide uptake may at times be negative.
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(Total 6 marks)
11. Explain the reactions involving the use of light energy that occur in the thylakoids of thechloroplast.
(Total 8 marks)
12. Explain how the light-independent reactions of photosynthesis rely on light-dependentreactions.
(Total 8 marks)
13. Outline the effect of temperature, light intensity and carbon dioxide concentration on the rate ofphotosynthesis.
(Total 6 marks)
14. Biosphere 2, an enormous greenhouse built in the Arizona desert in the USA, has been used tostudy five different ecosystems. It is a closed system so measurements can be made undercontrolled conditions. The effects of different factors, including changes in carbon dioxideconcentration in the greenhouse, were studied. The data shown below were collected over thecourse of one day in January 1996.
1200
1000
800
600
400
200
0
1600
1400
1200
1000
800
600
400
200
0
CO /ppm
light /mol m sμ
2–2 –1
0 1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24Time / hours
Key: CO Light
2
[Source: http://www.Ideo.columbia.edu/martins/climate_water/labs/lab6/labinstr6/html]
(a) (i) Identify the time of day when the sun rose.
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(ii) Identify the time of minimal CO2 concentration.
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(b) Determine the maximum difference in the concentration of CO2 over the 24-hour period.
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(c) Suggest reasons for changes in CO2 concentration during the 24-hour period.
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(Total 5 marks)
15. (a) Outline the induced fit model of enzyme activity.
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(b) (i) State two products of the light-dependent reactions of photosynthesis.
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(ii) Explain the light-independent reactions in photosynthesis.
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(Total 9 marks)
16. What is needed in photosynthesis to convert carbon dioxide into organic molecules?
A. Light and hydrogen from the splitting of water
B. Light and oxygen from the splitting of water
C. ATP and hydrogen from the splitting of water
D. ATP and oxygen from the splitting of water(1)
17. How is the proton gradient generated in chloroplasts during photosynthesis?
A. Flow of electrons from carrier to carrier in the thylakoid membrane causes pumping ofprotons across the thylakoid membrane.
B. Light causes protons to flow through protein channels in the thylakoid membrane.
C. Light splits water molecules in the stroma, causing the release of protons.
D. Protons are pumped across the thylakoid membrane using energy from ATP.(1)
18. Why is the action spectrum for photosynthesis similar to the absorption spectra ofphotosynthetic pigments?
A. Photosynthetic pigments have the same optimum temperature as the enzymes used inphotosynthesis.
B. Plants absorb the same photosynthetic pigments for use in photosynthesis.
C. Only wavelengths of light absorbed by pigments can be used in photosynthesis.
D. The amount of energy absorbed by photosynthetic pigments is equal to the activationenergy for photosynthesis.
(1)
19. (a) Draw and label the structure of the chloroplast as seen in the electron microscope.
(3)
(b) Explain the relationship between the structure of the chloroplast and its function.
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(c) Outline the process of chemiosmosis.
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(Total 7 marks)
20. (a) State where, in the chloroplast, the enzymes of the Calvin cycle are located.
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(b) Explain how the proton gradient in the chloroplast is generated by chemiosmosis.
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(c) Explain the relationship between the position of a leaf on a tree and the photosyntheticrate of the leaf.
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(Total 6 marks)
21. Pigments are extracted from the leaves of a green plant. White light is then passed through thesolution of pigments. What effect do the leaf pigments have on the white light?
A. Green wavelengths are absorbed and red and blue wavelengths are transmitted.
B. Red and blue wavelengths are absorbed and green wavelengths are transmitted.
C Blue wavelengths are absorbed and green and red wavelengths are transmitted.
D. Green and red wavelengths are absorbed and blue wavelengths are transmitted.(1)
