AQA A level Biology Revision questions and solutions
Describe how you would use a biochemical test to show that a solution contained a non-reducing sugar, such as sucrose
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[3] - answers,first reducing sugars test; boil with dilute HCl acid then Neutralise with NaHCǑ, add benedict and heat to 95
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degrees C brick red ppt forms if reducing sugar is present
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Describe a chemical test you could carry out to show that a piece of coconut contains lipids. [3] - answers(Crush in) ethan
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/ alcohol; Add (to) water (Order of adding is critical for this point); Emulsion / white colour
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Explain what is meant by a polymer. [1] - answersMolecule) made up of many identical/similar molecules/monomers/
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subunits;
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Name the reaction which occurs when starch is broken down into maltose. [1] - answersHydrolysis
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What is the formula for lactose? [2] - answersC12 ; H22Ō1
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Describe how β-glucose molecule differs from a molecule of α-glucose. [1] - answersH at top right end (instead of OH) / O
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at bottom (carbon 1)
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Show two ways in which the structure of cellulose is different from the structure of starch. [2] - answersStarch 1,4 and 1,6
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bonds / branching Cellulose 1,4 bonds / no 1,6 bonds / straight; starch All glucoses /monomers same way up cellulose
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Alternate glucoses upside down; starch Helix / coiled/compact cellulose Straight; Starch monomer Alpha glucose
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Cellulose monomer Beta glucose
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Describe the structure of starch and explain how its structure is related to its function. [3] - answersFormed from α glucos
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Joined by condensation/ by the removal of a water molecule/ glycosidic bonds; Between (carbons) 1 and 4 (and 1 and 6)
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Coiled chain; compact; (Allows) storage of large amount in a small space; Insoluble so has no effect on osmosis/water
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potential; Branches; (Allows) rapid breakdown/release of glucose / hydrolysis;
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The structure of a phospholipid molecule is different from that of a triglyceride. Describe how. [2] - answerstriglyceride ha
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three fatty acids and phospholipid has two; no phosphate group present in triglyceride but present in phospholipid.
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What is an unsaturated fatty acid? [1] - answersSome / two carbons with only one hydrogen / (double bonds) between
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carbon atoms / not saturated with hydrogen;
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Describe the structure of cellulose and explain how its structure is related to its function. [3] - answersAlternate β-glucos
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rotated 180o, long straight chains, Many hydrogen bonds join (polysaccharide) chains/molecules to each other / makes
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microfibrils / gives tensile strength;
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Which elements are found in proteins? [1] - answersCarbon, hydrogen, oxygen, nitrogen (sometimes sulphur)
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Describe how you would use a biochemical test to show that a solution contained protein. [2] - answersBiuret / alkali +
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copper sulphate; Lilac/purple/mauve/violet;
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Which bonds are found in a)Primary structure [1]b)Secondary structure [1] c)Tertiary structure [2] - answersa)Peptide b
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Hydrogen (and peptide) c)Ionic, disulphide bridges, hydrophobic interactions (hydrogen and peptide)
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,Explain how a change in the primary structure of a globular protein may result in a different three-dimensional structure. [
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- answersSequence of amino acids changes; tertiary structure changes/folds in a different way; bonds form in different
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places (not peptide);
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Describe how two-way chromatography is carried out. [2] - answersRun chromatogram then turn through 90/right angle
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With a different solvent;
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Explain the advantage of using two-way chromatography to separate short polypeptides. [2] - answersSpreads
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spots/polypeptides out more/ make sure spot only contains one substance;
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Explain how inhibitors affect the rate of enzyme-controlled reactions. [6] - answersStatement about two types, competit
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and non-competitive; Competitive: Similar shape to substrate;Inhibitor can enter/bind with active site (of enzyme);Non-
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competitive: Affect/bind to enzyme other than at active site; Distorts shape of active site; Inhibitors: Prevent entry ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro
of/binding of substrate to active site; Therefore fewer/no enzyme-substrate complexes formed;
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Describe and explain how an increase in temperature affects the rate of an enzyme controlled reaction. [5] - answersRat
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of reaction increases; Increasing temperature increases rate of movement of molecules/ kinetic energy; Collide more
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often/substrate enters active site more often/more enzyme-substrate complexes formed; Up to optimum; Rate of reacti
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decreases; High temperatures cause denaturation/loss of tertiary structure/3D structure; By breaking specified bonds
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(not peptide bond); Active site altered/substrate cannot bind/fit/
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An enzyme catalyses only one reaction. Explain why [2] - answers(Enzyme has) active site; Only substrate fits (the activ
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site);
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Describe the induced fit model of enzyme action. [2] - answersActive site / enzyme not complementary; Active site
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changes (shape) / is flexible; (Change in enzyme allows) substrate to fit / E-S complex to form;
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Describe one way that the lock and key model is different from the induced fit model. [1] - answersActive site does not
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change (shape) / is fixed (shape) / is rigid / does not wrap around substrate / (already) fits the substrate / is complementar
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(before binding);
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Explain why the rate of reaction of an enzyme is low away from its optimum pH. [3] - answers(change in pH) leads to
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breaking of bonds holding tertiary structure/ changes charge on amino acids; enzyme/protein/active site loses
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shape/denatured; substrate will not bind with/fit active site; fewer/no ES complexes formed;
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A protein molecule contains 150 amino acids. What is the total number of peptide bonds in this molecule? [1] - answers14
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How do you calculate magnification? [1] - answersM= I (Image)/ A (actual size)
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Describe the ways in which prokaryotic cells and eukaryotic cells differ. [3] - answersProkaryotic cells do not have a
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nucleus / have genetic material in cytoplasm; DNA in loop / ring; Not associated with proteins / do not have chromosome
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/chromatin / do not divide by mitosis; Smaller ribosomes; No membrane-bound organelles; Such as mitochondria /
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lysosomes / endoplasmic reticulum / Golgi / chloroplasts; Prokaryotic cells may have mesosomes; Prokaryotic cells
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smaller; May be enclosed by capsule;
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What is the function of: a)Ribosome b)Smooth ER c)Golgi apparatus d) Chloroplast e)Mitochondria [5] -
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answersa)Protein synthesis b)Lipid synthesis and transport c)Processing and packaging proteins for secretion
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d)Photosynthesis e)Aerobic respiration to produce ATP
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Explain the advantages and limitations of using a transmission electron microscope [5] - answersAdvantages: Small
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objects can be seen; TEM has high resolution as wavelength of electrons shorter; Limitations: Cannot look at living cells
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Describe how you would use a biochemical test to show that a solution contained a non-reducing sugar, such as sucrose
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[3] - answers,first reducing sugars test; boil with dilute HCl acid then Neutralise with NaHCǑ, add benedict and heat to 95
ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro
degrees C brick red ppt forms if reducing sugar is present
ro ro ro ro ro ro ro ro ro ro ro
Describe a chemical test you could carry out to show that a piece of coconut contains lipids. [3] - answers(Crush in) ethan
ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro
/ alcohol; Add (to) water (Order of adding is critical for this point); Emulsion / white colour
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Explain what is meant by a polymer. [1] - answersMolecule) made up of many identical/similar molecules/monomers/
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subunits;
ro
Name the reaction which occurs when starch is broken down into maltose. [1] - answersHydrolysis
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What is the formula for lactose? [2] - answersC12 ; H22Ō1
ro ro ro ro ro ro ro ro ro ro
Describe how β-glucose molecule differs from a molecule of α-glucose. [1] - answersH at top right end (instead of OH) / O
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at bottom (carbon 1)
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Show two ways in which the structure of cellulose is different from the structure of starch. [2] - answersStarch 1,4 and 1,6
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bonds / branching Cellulose 1,4 bonds / no 1,6 bonds / straight; starch All glucoses /monomers same way up cellulose
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Alternate glucoses upside down; starch Helix / coiled/compact cellulose Straight; Starch monomer Alpha glucose
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Cellulose monomer Beta glucose
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Describe the structure of starch and explain how its structure is related to its function. [3] - answersFormed from α glucos
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Joined by condensation/ by the removal of a water molecule/ glycosidic bonds; Between (carbons) 1 and 4 (and 1 and 6)
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Coiled chain; compact; (Allows) storage of large amount in a small space; Insoluble so has no effect on osmosis/water
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potential; Branches; (Allows) rapid breakdown/release of glucose / hydrolysis;
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The structure of a phospholipid molecule is different from that of a triglyceride. Describe how. [2] - answerstriglyceride ha
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three fatty acids and phospholipid has two; no phosphate group present in triglyceride but present in phospholipid.
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What is an unsaturated fatty acid? [1] - answersSome / two carbons with only one hydrogen / (double bonds) between
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carbon atoms / not saturated with hydrogen;
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Describe the structure of cellulose and explain how its structure is related to its function. [3] - answersAlternate β-glucos
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rotated 180o, long straight chains, Many hydrogen bonds join (polysaccharide) chains/molecules to each other / makes
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microfibrils / gives tensile strength;
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Which elements are found in proteins? [1] - answersCarbon, hydrogen, oxygen, nitrogen (sometimes sulphur)
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Describe how you would use a biochemical test to show that a solution contained protein. [2] - answersBiuret / alkali +
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copper sulphate; Lilac/purple/mauve/violet;
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Which bonds are found in a)Primary structure [1]b)Secondary structure [1] c)Tertiary structure [2] - answersa)Peptide b
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Hydrogen (and peptide) c)Ionic, disulphide bridges, hydrophobic interactions (hydrogen and peptide)
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1/ 10 ro roororor
,Explain how a change in the primary structure of a globular protein may result in a different three-dimensional structure. [
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- answersSequence of amino acids changes; tertiary structure changes/folds in a different way; bonds form in different
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places (not peptide);
ro ro ro
Describe how two-way chromatography is carried out. [2] - answersRun chromatogram then turn through 90/right angle
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With a different solvent;
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Explain the advantage of using two-way chromatography to separate short polypeptides. [2] - answersSpreads
ro ro ro ro ro ro ro ro ro ro ro ro ro
spots/polypeptides out more/ make sure spot only contains one substance;
ro ro ro ro ro ro ro ro ro ro
Explain how inhibitors affect the rate of enzyme-controlled reactions. [6] - answersStatement about two types, competit
ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro
and non-competitive; Competitive: Similar shape to substrate;Inhibitor can enter/bind with active site (of enzyme);Non-
ro ro ro ro ro ro ro ro ro ro ro ro ro ro
competitive: Affect/bind to enzyme other than at active site; Distorts shape of active site; Inhibitors: Prevent entry ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro
of/binding of substrate to active site; Therefore fewer/no enzyme-substrate complexes formed;
ro ro ro ro ro ro ro ro ro ro ro
Describe and explain how an increase in temperature affects the rate of an enzyme controlled reaction. [5] - answersRat
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of reaction increases; Increasing temperature increases rate of movement of molecules/ kinetic energy; Collide more
ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro
often/substrate enters active site more often/more enzyme-substrate complexes formed; Up to optimum; Rate of reacti
ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro
decreases; High temperatures cause denaturation/loss of tertiary structure/3D structure; By breaking specified bonds
ro ro ro ro ro ro ro ro ro ro ro ro ro
(not peptide bond); Active site altered/substrate cannot bind/fit/
ro ro ro ro ro ro ro ro
An enzyme catalyses only one reaction. Explain why [2] - answers(Enzyme has) active site; Only substrate fits (the activ
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site);
ro
Describe the induced fit model of enzyme action. [2] - answersActive site / enzyme not complementary; Active site
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changes (shape) / is flexible; (Change in enzyme allows) substrate to fit / E-S complex to form;
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Describe one way that the lock and key model is different from the induced fit model. [1] - answersActive site does not
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change (shape) / is fixed (shape) / is rigid / does not wrap around substrate / (already) fits the substrate / is complementar
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(before binding);
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Explain why the rate of reaction of an enzyme is low away from its optimum pH. [3] - answers(change in pH) leads to
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breaking of bonds holding tertiary structure/ changes charge on amino acids; enzyme/protein/active site loses
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shape/denatured; substrate will not bind with/fit active site; fewer/no ES complexes formed;
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A protein molecule contains 150 amino acids. What is the total number of peptide bonds in this molecule? [1] - answers14
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How do you calculate magnification? [1] - answersM= I (Image)/ A (actual size)
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Describe the ways in which prokaryotic cells and eukaryotic cells differ. [3] - answersProkaryotic cells do not have a
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nucleus / have genetic material in cytoplasm; DNA in loop / ring; Not associated with proteins / do not have chromosome
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/chromatin / do not divide by mitosis; Smaller ribosomes; No membrane-bound organelles; Such as mitochondria /
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lysosomes / endoplasmic reticulum / Golgi / chloroplasts; Prokaryotic cells may have mesosomes; Prokaryotic cells
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smaller; May be enclosed by capsule;
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What is the function of: a)Ribosome b)Smooth ER c)Golgi apparatus d) Chloroplast e)Mitochondria [5] -
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answersa)Protein synthesis b)Lipid synthesis and transport c)Processing and packaging proteins for secretion
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d)Photosynthesis e)Aerobic respiration to produce ATP
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Explain the advantages and limitations of using a transmission electron microscope [5] - answersAdvantages: Small
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objects can be seen; TEM has high resolution as wavelength of electrons shorter; Limitations: Cannot look at living cells
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2/ 10 ro roororor
