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Transcript of Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Pre Quiz – Share a sheet...
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Pre Quiz –
• Share a sheet a paper so everyone has a half sheet. Fold your half in half and number to 9.
• Turn to question 20 in your lecture guide. Take 5 minutes and see how many of these you can answer.
• Use your reading guide if you have it.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
1. Overview: The Molecules of Life
• Within cells, small organic molecules are joined together to form larger molecules
• The four classes include:
– Carbohydrates, Lipids, Proteins, Nucleic Acids
• Macromolecules are large molecules composed of thousands of covalently connected atoms
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
2-3. Concept 5.1: Most macromolecules are polymers, built from monomers
• Three of the four classes of life’s organic molecules are polymers:
– Carbohydrates
– Proteins
– Nucleic acids
• A polymer is a long molecule consisting of many similar building blocks called monomers
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
4,5,6. The Synthesis and Breakdown of Polymers
• Monomers link up by condensation reactions called dehydration reactions
• Polymers are broken down to monomers by hydrolysis, a reaction that is essentially the reverse of the dehydration reaction
• Hydro- water
• Lysis – break
Animation: Polymers
LE 5-2
Short polymer Unlinked monomer
Dehydration removes a watermolecule, forming a new bond
Dehydration reaction in the synthesis of a polymer
Longer polymer
Hydrolysis adds a watermolecule, breaking a bond
Hydrolysis of a polymer
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
7. Consider the reaction
• Where does the water go?
• What kind of reaction is it?
• Is glucose a monomer or polymer?
• To summarize, when two monomers are joined, a molecule of _________is always removed.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The Diversity of Polymers
• Each cell has thousands of different kinds of macromolecules
• Macromolecules vary among cells of an organism, vary more within a species, and vary even more between species
• An immense variety of polymers can be built from a small set of monomers
1 2 3 HOH
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
8. Concept 5.2: Carbohydrates serve as fuel and building material
• Carbohydrates include sugars and the polymers of sugars
• The simplest carbohydrates are monosaccharides, or single sugars
• Carbohydrate macromolecules are polysaccharides, polymers composed of many sugar building blocks
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
9. Sugars
• Monosaccharides have molecular formulas that are usually multiples of CH2O
• Glucose is the most common monosaccharide
9. What is the formula of a hexose sugar?
CnH2nOn
LE 5-3Triose sugars
(C3H6O3)
GlyceraldehydeAld
ose
sK
eto
s es
Pentose sugars(C5H10O5)
Ribose
Hexose sugars(C5H12O6)
Glucose Galactose
Dihydroxyacetone
Ribulose
Fructose
10-12
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Monosaccharides serve as a major fuel for cells and as building blocks for other molecules
• Though often drawn as a linear skeleton, in aqueous solutions they form rings
13.
LE 5-4
Linear andring forms
Abbreviated ringstructure
13. Where are all the carbons in the abbreviated ring?
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• A disaccharide =mono + mono
• What type of reaction bonds them together?
• This covalent bond is called a glycosidic linkage
Animation: Disaccharides
14.
LE 5-5
Glucose
Maltose
Fructose Sucrose
Glucose Glucose
Dehydrationreaction in thesynthesis of maltose
Dehydrationreaction in thesynthesis of sucrose
1–4glycosidic
linkage
1–2glycosidic
linkage
14.
15. What does –ose mean?
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
16. Glycosidic Linkage.
• A Glycosidic linkage is a covalent bond formed between two monosaccharides by a dehydration reaction.
• 1-4 glycosidic linkages
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Polysaccharides
• Polysaccharides have storage and structural roles
• The structure and function is determined by its monomers and the positions of glycosidic linkages
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
18. Storage Polysaccharides
• Starch, a storage polysaccharide of plants, consists entirely of glucose monomers
• Plants store surplus starch as granules within chloroplasts and other plastids
LE 5-6aChloroplast Starch
1 µm
Amylose
Starch: a plant polysaccharide
Amylopectin
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Glycogen is a storage polysaccharide in animals
• Humans and other vertebrates store glycogen mainly in liver and muscle cells
LE 5-6bMitochondria Glycogen granules
0.5 µm
Glycogen
Glycogen: an animal polysaccharide
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
18. Structural Polysaccharides
• Cellulose is a major component of the tough wall of plant cells
• Like starch, cellulose is a polymer of glucose, but the glycosidic linkages differ
• The difference is based on two ring forms for glucose: alpha () and beta ()
Animation: Polysaccharides
LE 5-7
a Glucose
a and b glucose ring structures
b Glucose
Starch: 1–4 linkage of a glucose monomers.
Cellulose: 1–4 linkage of b glucose monomers.
LE 5-8
Cellulosemolecules
Cellulose microfibrilsin a plant cell wall
Cell walls Microfibril
Plant cells
0.5 µm
Glucosemonomer
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Enzymes that digest starch by hydrolyzing alpha linkages can’t hydrolyze beta linkages in cellulose
• Cellulose in human food passes through the digestive tract as insoluble fiber
• Some microbes use enzymes to digest cellulose
• Many herbivores, from cows to termites, have symbiotic relationships with these microbes
19.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Chitin, another structural polysaccharide, is found in the exoskeleton of arthropods
• Chitin also provides structural support for the cell walls of many fungi
• Chitin can be used as surgical thread
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
21. Concept 5.3: Lipids are a diverse group of hydrophobic molecules
• Lipids do not form polymers
• Lipids have little or no affinity for water
• Lipids are hydrophobic becausethey consist mostly of hydrocarbons, which form nonpolar covalent bonds (remember?)
• The most biologically important lipids are fats, phospholipids, and steroids
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
22. Fats
• Fats = glycerol + 3 fatty acids
• Glycerol is a three-carbon alcohol with a hydroxyl group attached to each carbon
• A fatty acid consists of a carboxyl group attached to a long carbon skeleton
Animation: FatsAnimation: Fats
LE 5-11a
Dehydration reaction in the synthesis of a fat
Glycerol
Fatty acid(palmitic acid)
23. How many water molecules are removed? What is this process called?
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Fats separate from water because water molecules form hydrogen bonds with each other and exclude the fats
• In a fat, three fatty acids are joined to glycerol by an ester linkage, a bond between a hydroxyl group and carboxyl group, creating a:
• Fat molecule = triacylglycerol = triglyceride
24
LE 5-11b
Ester linkage
Fat molecule (triacylglycerol)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Fatty acids vary in length (number of carbons) and in the number and locations of double bonds
• Saturated fatty acids have the maximum number of hydrogen atoms possible and no double bonds
• Unsaturated fatty acids have one or more double bonds
• The major function of fats is energy storage
25.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Fats made from saturated fatty acids are called saturated fats
• Most animal fats are saturated
• Saturated fats are solid at room temperature
• A diet rich in saturated fats may contribute to cardiovascular disease through plaque deposits
26.
LE 5-12a
Saturated fat and fatty acid.
Stearic acid
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Fats made from unsaturated fatty acids are called unsaturated fats
• Plant fats and fish fats are usually unsaturated
• Plant fats and fish fats are liquid at room temperature and are called oils
28. The kinks in the fatty acid tail prevent unsaturated fats from packing together closely
enough to solidify at room temperature.
27.
LE 5-12b
Unsaturated fat and fatty acid.
Oleic acid
cis double bondcauses bending
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
29. Trans fats
• Hydrogenated oils – synthetically converted to saturated fat by adding hydrogen
– Prevents lipids from liquefying in peanut butter and margarine
• Trans fats – caused by hydrogenating process, has a trans double bond
– Contribute more that saturated fats to atherosclerosis
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
30. Four important functions of fats.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
31. Phospholipids
• A phospholipid = glycerol + 2 fatty acids + a phosphate group
• The two fatty acid tails are hydrophobic, but the phosphate group and its attachments form a hydrophilic head
LE 5-13
Structural formula Space-filling model Phospholipid symbol
Hydrophilichead
Hydrophobictails
Fatty acids
Choline
Phosphate
Glycerol
Hyd
rop
ho
bic
tai
lsH
ydr o
ph
ilic
hea
d
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• When phospholipids are added to water, they self-assemble into a bilayer, with the hydrophobic tails pointing toward the interior
– Tails are hydrophobic because of the non polar covalent bond of the hydrocarbons
• The structure of phospholipids results in a bilayer arrangement found in cell membranes
• Phospholipids are the major component of all cell membranes
32.
LE 5-14
WATERHydrophilichead
Hydrophobictails
WATER
34 - 35
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36.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
37. Steroids
• Steroids = a carbon skeleton consisting of four fused rings
• Cholesterol, an important steroid, is a component in animal cell membranes
• Although cholesterol is essential in animals, high levels in the blood may contribute to cardiovascular disease
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 5.4: Proteins have many structures, resulting in a wide range of functions
• Proteins account for more than 50% of the dry mass of most cells
• Protein functions include structural support, storage, transport, cellular communications, movement, and defense against foreign substances
• In other words, proteins are abundant and important!!!
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
38.
LE 5-16
Substrate(sucrose)
Enzyme(sucrose)
Fructose
Glucose
39
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Enzymes are protein catalysts
• That means they speed up chemical reactions
• Enzymes can perform their functions repeatedly, functioning as “workhorses” that carry out the processes of life
40. Is this reaction dehydration synthesis or hydrolysis?
39.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Polypeptides
• Polypeptides are polymers of amino acids
• A protein consists of one or more polypeptides
LE 5-UN78
Aminogroup
Carboxylgroup
carbon41.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
42. Amino Acid Monomers
• Amino acids are organic molecules with carboxyl and amino groups
• Amino acids differ in their properties due to differing side chains, called R groups
• Cells use 20 amino acids to make thousands of proteins
LE 5-17a
Isoleucine (Ile)
Methionine (Met) Phenylalanine (Phe) Tryptophan (Trp) Proline (Pro)
Leucine (Leu)Valine (Val)Alanine (Ala)
Nonpolar
Glycine (Gly)
43.
LE 5-17b
Asparagine (Asn) Glutamine (Gln)Threonine (Thr)
Polar
Serine (Ser) Cysteine (Cys) Tyrosine (Tyr)
43.
LE 5-17c
Electricallycharged
Aspartic acid (Asp)
Acidic Basic
Glutamic acid (Glu) Lysine (Lys) Arginine (Arg) Histidine (His)
43.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
44. Amino Acid Polymers
• Amino acids are linked by peptide bonds
• A polypeptide is a polymer of amino acids
• Polypeptides range in length from a few monomers to more than a thousand
• Each polypeptide has a unique linear sequence of amino acids called its primary structure
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Protein Conformation and Function
• A functional protein consists of one or more polypeptides twisted, folded, and coiled into a unique shape
• The sequence of amino acids determines a protein’s three-dimensional conformation
• A protein’s conformation determines its function
• Ribbon models and space-filling models can depict a protein’s conformation
LE 5-19
A ribbon model
Groove
Groove
A space-filling model
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
45. Four Levels of Protein Structure
• The primary structure of a protein is its unique sequence of amino acids
• Secondary structure, found in most proteins, consists of coils and folds in the polypeptide chain
• Tertiary structure is determined by interactions among various side chains (R groups)
• Quaternary structure results when a protein consists of multiple polypeptide chains
Animation: Protein Structure IntroductionAnimation: Protein Structure Introduction
LE 5-20
Amino acidsubunits
pleated sheet+H3N
Amino end
helix
45-46
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Primary structure, the sequence of amino acids in a protein, is like the order of letters in a long word
• Primary structure is determined by inherited genetic information
Animation: Primary Protein StructureAnimation: Primary Protein Structure
LE 5-20a
Amino acidsubunits
Carboxyl end
Amino end
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• The coils and folds of secondary structure result from hydrogen bonds between repeating parts of the polypeptide backbone
• The two types of secondary structure are:
– Alpha helix
– Beta pleated sheet
Animation: Secondary Protein StructureAnimation: Secondary Protein Structure
LE 5-20b
Amino acidsubunits
pleated sheet
helix
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Tertiary structure is determined by interactions between R groups, rather than interactions between backbone constituents
• These interactions between R groups include hydrogen bonds, ionic bonds, hydrophobic interactions, and van der Waals interactions
• Strong covalent bonds called disulfide bridges may reinforce the protein’s conformation
Animation: Tertiary Protein StructureAnimation: Tertiary Protein Structure
LE 5-20d
Hydrophobicinteractions andvan der Waalsinteractions
Polypeptidebackbone
Disulfide bridge
Ionic bond
Hydrogenbond
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Quaternary structure results when two or more polypeptide chains form one macromolecule
• Example: Collagen is a fibrous protein consisting of three polypeptides coiled like a rope
• Example: Hemoglobin is a globular protein consisting of four polypeptides: two alpha and two beta chains
Animation: Quaternary Protein StructureAnimation: Quaternary Protein Structure
LE 5-20e
Chains
ChainsHemoglobin
IronHeme
CollagenPolypeptide chain
Polypeptidechain
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
PowerPoint Lectures for Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
LE 5-20d
Hydrophobicinteractions andvan der Waalsinteractions
Polypeptidebackbone
Disulfide bridge
Ionic bond
Hydrogenbond
47.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
48. Sickle-Cell Disease: A Simple Change in Primary Structure
• A slight change in primary structure can affect a protein’s conformation and ability to function
• Example: Sickle-cell disease, an inherited blood disorder, results from a single amino acid substitution in the protein hemoglobin
LE 5-21a
Red bloodcell shape
Normal cells arefull of individualhemoglobinmolecules, eachcarrying oxygen.
10 µm 10 µm
Red bloodcell shape
Fibers of abnormalhemoglobin deformcell into sickleshape.
LE 5-21b
Primarystructure
Secondaryand tertiarystructures
1 2 3
Normal hemoglobin
Val His Leu
4Thr
5Pro
6Glu Glu
7Primarystructure
Secondaryand tertiarystructures
1 2 3
Sickle-cell hemoglobin
Val His Leu
4Thr
5Pro
6Val Glu
7
Quaternarystructure
Normalhemoglobin(top view)
Function Molecules donot associatewith oneanother; eachcarries oxygen.
Quaternarystructure
Sickle-cellhemoglobin
Function Molecules interact withone another tocrystallize intoa fiber; capacityto carry oxygenis greatly reduced.
Exposedhydrophobicregion subunit subunit
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
49. What Determines Protein Conformation?
• In addition to primary structure, physical and chemical conditions can affect conformation
• Changes in pH, salt concentration, temperature, or other environmental factors can cause a protein to unravel
• This loss of a protein’s native conformation is called denaturation
• A denatured protein is biologically inactive
LE 5-22
Denaturation
Renaturation
Denatured proteinNormal protein
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
50. The Protein-Folding Problem
• It is hard to predict a protein’s conformation from its primary structure
• Most proteins probably go through several states on their way to a stable conformation
• Chaperonins are protein molecules that assist the proper folding of other proteins
LE 5-23a
Chaperonin(fully assembled)
Hollowcylinder
Cap
LE 5-23b
Polypeptide
Correctlyfoldedprotein
An unfolded poly-peptide enters thecylinder from oneend.
Steps of ChaperoninAction:
The cap comesoff, and theproperly foldedprotein is released.
The cap attaches, causingthe cylinder to changeshape in such a way that it creates a hydrophilicenvironment for thefolding of the polypeptide.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Pre Quiz
• Turn to page 11 question 51
• Try to answer this questions with your background knowledge from Biology and your reading guide
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 5.5: Nucleic acids store and transmit hereditary information
• The amino acid sequence of a polypeptide is programmed by a unit of inheritance called a gene
• Genes are made of DNA, a nucleic acid• There are two types of nucleic acids:
– Deoxyribonucleic acid (DNA)– Ribonucleic acid (RNA)
• DNA provides directions for its own replication
• DNA directs synthesis of messenger RNA (mRNA) and, through mRNA, controls protein synthesis
• Protein synthesis occurs in ribosomes
LE 5-25
NUCLEUS
DNA
CYTOPLASM
mRNA
mRNA
Ribosome
Aminoacids
Synthesis ofmRNA in the nucleus
Movement ofmRNA into cytoplasmvia nuclear pore
Synthesis of protein
Polypeptide
51.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The Structure of Nucleic Acids
• Nucleic acids are polymers called polynucleotides
• Each polynucleotide is made of monomers called nucleotides
• Each nucleotide consists of a nitrogenous base, a pentose sugar, and a phosphate group
LE 5-26a5 end
3 end
Nucleoside
Nitrogenousbase
Phosphategroup
Nucleotide
Polynucleotide, ornucleic acid
Pentosesugar
52-53.
LE 5-26bNitrogenous bases
Pyrimidines
Purines
Pentose sugars
CytosineC
Thymine (in DNA)T
Uracil (in RNA)U
AdenineA
GuanineG
Deoxyribose (in DNA)
Nucleoside components
Ribose (in RNA)
54.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
56. Nucleotide Monomers
• There are two families of nitrogenous bases:
– Pyrimidines have a single ring structure (cytosine and thymine and uracil)
– Purines have a double ring structure (adenine and guanine)
• In DNA, the sugar is deoxyribose
• In RNA, the sugar is ribose
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Nucleotide Polymers
• Nucleotides are joined by covalent bonds that form between the –OH group on the 3´ carbon of one nucleotide and the phosphate on the 5´ carbon on the next
• These links create a “sugar-phosphate backbone”
• The sequence of bases along a DNA or mRNA polymer is unique for each gene
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
58-59. The DNA Double Helix
• A DNA molecule has two polynucleotides spiraling around an imaginary axis, forming a double helix
• In the DNA double helix, the two backbones run in opposite 5´ to 3´ directions from each other, an arrangement referred to as antiparallel
• One DNA molecule includes many genes
• The nitrogenous bases in DNA form hydrogen bonds in a complementary fashion: A always with T, and G always with C
LE 5-27
Sugar-phosphatebackbone
3 end5 end
Base pair (joined byhydrogen bonding)
Old strands
Nucleotideabout to beadded to anew strand
5 end
New strands
3 end
5 end3 end
5 end
60.-63.