Term 1Revision Biology 12. Cell membranes Sketch a typical cell membrane according to the Fluid...
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![Page 1: Term 1Revision Biology 12. Cell membranes Sketch a typical cell membrane according to the Fluid Mosaic model Describe the roles of: Phospholipids Proteins.](https://reader036.fdocuments.in/reader036/viewer/2022083004/56649da25503460f94a8ec37/html5/thumbnails/1.jpg)
Term 1Revision
Biology 12
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Cell membranesSketch a typical cell membrane according to the Fluid Mosaic model
Describe the roles of:• Phospholipids
• Proteins
• Carbohydrates
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CellsSketch a typical cell membrane according to the Fluid Mosaic model .
Describe the roles of:Phospholipids = A – waterproof, flexible layer, that lets in small particles
Proteins = B – provides channels for larger particles (facilitated diffusions), acts as pumps (active transport), acts as receptor sites
Carbohydrates = C - acts as receptor sites
A
B
C
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Exchange of material
Show the movements of water and ions that would occur in both these cases
Distilled water Sea water
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Exchange of material
Show the movements of water and ions that would occur in both these cases
Distilled water Sea water
Water moves in
Water moves out Ions move inIons move out
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TEE Extended answer 2003 36a
Genetic information is stored in molecules of DNA. Using labelled diagrams describe the structure of DNA at the level of major
components and describe how it carries genetic information
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Extended answer 2003 36a) Genetic information is stored in molecules of DNA. Using labelled diagrams describe the structure of DNA at the level of major components
and describe how it carries genetic informationOne mark/dot point in answers below unless otherwise indicated. Maximum 10
marks/question.
Diagram – showing nitrogenous base pairs - A T, C G, and sugar phosphate backbone• one mark for nitrogenous pairs label on the figure, 2 marks for sugar phosphate
backbone label(3 marks total)• nucleotides• double helix• one mark for correct basic structure in the figure• name bases (one mark for naming all 4)• indicate pairing (each correct pairing = one mark)• sequence of bases codes for amino acid structure• triplet code/codons• relationship to amino acidsThe information is carried within the DNA by the sequence of base pairs. Each segment
of 3 nucleotides codes for one amino acid & is called a codonThis information is copied to mRNA in the nucleus and carried to the ribosomes,
determining which proteins are made
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Structure of DNA
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Structure of DNAnucleotides
Adenine
Guanine
sugar
phosphate
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Protein synthesis• Transcription• Translation• Codon• Anticodon• t-RNA• m-RNA• r-RNA• Protein• Amino acid
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Protein synthesis• Transcription – copying of RNA from DNA• Translation – reading of mRNA at ribosome• Codon – 3 nucleotide section on mRNA that codes
for an amino acid• Anticodon - 3 nucleotide section on tRNA that
matches codon, tRNA brings the right amino acid• t-RNA – carries amino acid• m-RNA – codes for sequence of amino acids• r-RNA – makes up ribosomes• Protein – long chain of amino acids (end product)• Amino acid – unit that is put together to make
protein
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DNA replication• Occurs in • One set of enzymes • Another set of enzymes• Nucleotides match up by the
(C , A )
• The end result is joined at a point called the
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DNA replication• Occurs in nucleus • One set of enzymes splits DNA• Another set of enzymes adds
new nucleotides• Nucleotides match up by the
base pairing rule (C - G, A - T )
• The end result is 2 strands (chromatids) joined at a point called the centromere
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Stages of mitosis
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Stages of mitosis
• Interphase – normal cell metabolism & growth, DNA replication
• Prophase – nucleus disappears, spindle forms, chromosomes condense & become visible
• Metaphase – chromosomes line up on equator• Anaphase – chromatids split & move to opposite
ends of cell• Telophase – new nuclei form, cytoplasm divides
to form 2 new cells• Interphase - normal cell metabolism & growth
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Identify the stages of mitosis
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Identify the stages of mitosis
telophase
anaphase
metaphase
interphase
prophase
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TEE - Extended answer 2002 36dMost genes in the body carry information about the structure of enzymes,
highlighting the importance of enzymes to cellular function.
Describe the functions of enzymes in cells and explain why enzymes are so specific in their action.
Discuss the factors that affect enzyme activity, and describe their effects
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Extended answer 2002 36d)Most genes in the body carry information about the structure of enzymes, highlighting the
importance of enzymes to cellular function.Describe the functions of enzymes in cells and explain why enzymes are so specific in their
action.Functions of Enzymes (max 7 marks):• catalysis • speed up reactions• reduce activation energy • synthesis / anabolism & example• digestion / catabolism & example • energy production & example• control of chemical pathways / energy productionEnzyme Specificity:• Caused by active site / 3D shape• Formation of enzyme – substrate complex / lock & key model• Good diagram of lock & key model• Enzymes work within narrow pH ranges• Enzymes work within narrow temperature rangesDiscuss the factors that affect enzyme activity, and describe their effects• Increasing temperature increases activity, unless it gets too hot and the enzyme is
destroyed• Changing pH alters shape of enzyme reduces activity• Increasing substrate concentration increases activity (up to maximum)• Increasing enzyme concentration increases activity (up to maximum)• Decreasing product concentration decreases activity• Increasing cofactor concentration increases activity (up to maximum)• Presence of inhibitors decreases activity