AQA A-Level Biology Mark Scheme and Specification Bank EXPERT
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Hydrolysis - (ANSWER)Breaks a chemical bonds between two molecules; Using water;
Glycogen - (ANSWER)Polysaccharide of α-glucose; (Joined by) glycosidic bonds; Branched
structure;
Cellulose - (ANSWER)Made up of β-glucose (monomers); Cellulose molecule has straight
chain and glycogen is branched; Glycogen has 1,4- and 1,6- glycosidic bonds and cellulose has
only 1,4- glycosidic bonds;
Glycogen Structure Related to Function - (ANSWER)Insoluble (in water), so doesn't affect
water potential; Branched / coiled心的坚强决定了我们的命运。当
/ (α-)helix, so makes molecule compact; Polymer of (α-
)glucose so provides glucose for respiration; Branched / more ends for fast breakdown / enzyme
action; Large (molecule), so can't 我们面对挫折时，是一颗不屈的
cross the cell membrane;
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Starch Properties - (ANSWER)Insoluble; Don't affect water potential; Helical; Compact; Large
molecule; Cannot leave cell;
Phospholipids vs Triglycerides - (ANSWER)Both contain ester bonds (between glycerol and
fatty acid); Both contain glycerol; Fatty acids on both may be saturated or unsaturated; Both are
insoluble in water; Both contain C, H and O but phospholipids also contain P; Triglyceride has
three fatty acids and phospholipid has two fatty acids plus phosphate group; Triglycerides are
hydrophobic/non-polar and phospholipids have hydrophilic/polar and hydrophobic/polar region;
Phospholipids form monolayer (on surface)/micelle/bilayer (in water) but triglycerides don't;
Protein Structure - (ANSWER)Polymer of amino acids; Joined by peptide bonds; Formed by
condensation; Primary structure is order of amino acids; Secondary structure is folding of
polypeptide chain due to hydrogen bonding; Tertiary structure is 3-D folding due to hydrogen
bonding and ionic/disulfide bonds; Quaternary structure is two or more polypeptide chains;
,Induced Fit Model - (ANSWER)(before reaction) active site not complementary to/does not fit
substrate; Shape of active site changes as substrate binds/as enzyme-substrate complex forms;
Stressing/distorting/bending bonds (in substrate leading to reaction);
Increased Temperature and Reaction Rate - (ANSWER)Particles have more kinetic energy;
therefore they move more; so there are more collisions between substrates and active sites; so
more ES complexes form;
Enzyme Denaturation - (ANSWER)Heat above the optimum breaks hydrogen bonds; this
causes the tertiary structure to unfold; so the active site changes shape; substrate can no longer
bind to the active site, as it's no longer complementary; so fewer ES complexes form;
Effect of Changes in pH - (ANSWER)Ionic bonds holding tertiary structure break; active site
distorts and substrate no longer binds to active site; charges on amino acids in active site
affected; fewer ES complexes form;
心的坚强决定了我们的命运。当
我们面对挫折时，是一颗不屈的
Concentration of Substrate - (ANSWER)(Rate of) increase in concentration of product slows as
心让我们勇敢前行
substrate is used up OR High initial rate as plenty of substrate/more E-S complexes; No increase
after 25 minutes/at end/levels off because no substrate left;
Temperature Graph of Enzyme Rate - (ANSWER)Initial rate of reaction faster at 37 °C (than 25
°C); Because more kinetic energy; So more E-S collisions/more E-S complexes formed; Graph
reaches plateau /levels off at 37 °C; Because all substrate used up;
Competitive vs Non-Competitive Inhibition - (ANSWER)Competitive inhibitor binds to active
sites of enzyme but non-competitive inhibitor binds at allosteric site/away from active site;
(Binding of) competitive inhibitor does not cause change in shape of active site but (binding of)
non-competitive does (cause change in size of active site); So with competitive inhibitor, at high
substrate concentrations (active) enzyme still available but with non-competitive inhibitor
(active) enzymes no longer available; At higher substrate concentrations likelihood of enzyme-
substrate collisions increases with competitive inhibitor but this is not possible with non-
competitive inhibitor;
, Effect of Temperature on Plant Growth - (ANSWER)Enzyme activity reduced/(some) enzymes
denatured; Less photosynthesis, so fewer sugars formed (plants only); Less (complex) biological
molecules/organic substances made (that add to mass); Less respiration; Less energy/ATP for
growth; Less energy for named function associated with growth (eg mitosis);
DNA Replication - (ANSWER)Helicase unzips DNA double helix by breaking hydrogen
bonds; free DNA nucleotides in the nucleus complementary base pair OR A to T and C to G;
with exposed bases on both strands; hydrogen bonds between complementary base pairs reform;
both strands act as a template; DNA polymerase (causes); Nucleotides to join together (to form
new strand)/phosphodiester bonds to form;
Semi-Conservative Replication - (ANSWER)Idea of both original strands being copied/both are
template strands; Each new DNA molecule consists of one original and one new strand of DNA;
ATP Uses and Properties - (ANSWER)Releases relatively small amount of energy / little energy
心的坚强决定了我们的命运。当
lost as heat; Releases energy instantaneously; Phosphorylates other compounds, making them
more reactive; Can be rapidly re-synthesised; Does not leave cells;
我们面对挫折时，是一颗不屈的
心让我们勇敢前行
ATP Structure vs DNA Nucleotide - (ANSWER)ATP has ribose and DNA has deoxyribose;
ATP has 3 phosphates and DNA nucleotide has one phosphate; Base is always adenine in ATP
and bases vary in DNA nucleotide (A,C,G or T);
Water Properties - (ANSWER)A metabolite in
condensation/hydrolysis/photosynthesis/respiration; A solvent so (metabolic) reactions can
occur; High heat capacity so buffers changes in temperature; Large latent heat of vaporisation so
provides a cooling effect (through evaporation); Cohesion (between water molecules) so supports
columns of water (in plants); Cohesion (between water molecules) so produces surface tension
supporting organisms;
High heat capacity - (ANSWER)Buffers temperature changes in biological systems.
Latent heat of vaporisation - (ANSWER)Cooling effect through evaporation of water.
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Hydrolysis - (ANSWER)Breaks a chemical bonds between two molecules; Using water;
Glycogen - (ANSWER)Polysaccharide of α-glucose; (Joined by) glycosidic bonds; Branched
structure;
Cellulose - (ANSWER)Made up of β-glucose (monomers); Cellulose molecule has straight
chain and glycogen is branched; Glycogen has 1,4- and 1,6- glycosidic bonds and cellulose has
only 1,4- glycosidic bonds;
Glycogen Structure Related to Function - (ANSWER)Insoluble (in water), so doesn't affect
water potential; Branched / coiled心的坚强决定了我们的命运。当
/ (α-)helix, so makes molecule compact; Polymer of (α-
)glucose so provides glucose for respiration; Branched / more ends for fast breakdown / enzyme
action; Large (molecule), so can't 我们面对挫折时，是一颗不屈的
cross the cell membrane;
心让我们勇敢前行
Starch Properties - (ANSWER)Insoluble; Don't affect water potential; Helical; Compact; Large
molecule; Cannot leave cell;
Phospholipids vs Triglycerides - (ANSWER)Both contain ester bonds (between glycerol and
fatty acid); Both contain glycerol; Fatty acids on both may be saturated or unsaturated; Both are
insoluble in water; Both contain C, H and O but phospholipids also contain P; Triglyceride has
three fatty acids and phospholipid has two fatty acids plus phosphate group; Triglycerides are
hydrophobic/non-polar and phospholipids have hydrophilic/polar and hydrophobic/polar region;
Phospholipids form monolayer (on surface)/micelle/bilayer (in water) but triglycerides don't;
Protein Structure - (ANSWER)Polymer of amino acids; Joined by peptide bonds; Formed by
condensation; Primary structure is order of amino acids; Secondary structure is folding of
polypeptide chain due to hydrogen bonding; Tertiary structure is 3-D folding due to hydrogen
bonding and ionic/disulfide bonds; Quaternary structure is two or more polypeptide chains;
,Induced Fit Model - (ANSWER)(before reaction) active site not complementary to/does not fit
substrate; Shape of active site changes as substrate binds/as enzyme-substrate complex forms;
Stressing/distorting/bending bonds (in substrate leading to reaction);
Increased Temperature and Reaction Rate - (ANSWER)Particles have more kinetic energy;
therefore they move more; so there are more collisions between substrates and active sites; so
more ES complexes form;
Enzyme Denaturation - (ANSWER)Heat above the optimum breaks hydrogen bonds; this
causes the tertiary structure to unfold; so the active site changes shape; substrate can no longer
bind to the active site, as it's no longer complementary; so fewer ES complexes form;
Effect of Changes in pH - (ANSWER)Ionic bonds holding tertiary structure break; active site
distorts and substrate no longer binds to active site; charges on amino acids in active site
affected; fewer ES complexes form;
心的坚强决定了我们的命运。当
我们面对挫折时，是一颗不屈的
Concentration of Substrate - (ANSWER)(Rate of) increase in concentration of product slows as
心让我们勇敢前行
substrate is used up OR High initial rate as plenty of substrate/more E-S complexes; No increase
after 25 minutes/at end/levels off because no substrate left;
Temperature Graph of Enzyme Rate - (ANSWER)Initial rate of reaction faster at 37 °C (than 25
°C); Because more kinetic energy; So more E-S collisions/more E-S complexes formed; Graph
reaches plateau /levels off at 37 °C; Because all substrate used up;
Competitive vs Non-Competitive Inhibition - (ANSWER)Competitive inhibitor binds to active
sites of enzyme but non-competitive inhibitor binds at allosteric site/away from active site;
(Binding of) competitive inhibitor does not cause change in shape of active site but (binding of)
non-competitive does (cause change in size of active site); So with competitive inhibitor, at high
substrate concentrations (active) enzyme still available but with non-competitive inhibitor
(active) enzymes no longer available; At higher substrate concentrations likelihood of enzyme-
substrate collisions increases with competitive inhibitor but this is not possible with non-
competitive inhibitor;
, Effect of Temperature on Plant Growth - (ANSWER)Enzyme activity reduced/(some) enzymes
denatured; Less photosynthesis, so fewer sugars formed (plants only); Less (complex) biological
molecules/organic substances made (that add to mass); Less respiration; Less energy/ATP for
growth; Less energy for named function associated with growth (eg mitosis);
DNA Replication - (ANSWER)Helicase unzips DNA double helix by breaking hydrogen
bonds; free DNA nucleotides in the nucleus complementary base pair OR A to T and C to G;
with exposed bases on both strands; hydrogen bonds between complementary base pairs reform;
both strands act as a template; DNA polymerase (causes); Nucleotides to join together (to form
new strand)/phosphodiester bonds to form;
Semi-Conservative Replication - (ANSWER)Idea of both original strands being copied/both are
template strands; Each new DNA molecule consists of one original and one new strand of DNA;
ATP Uses and Properties - (ANSWER)Releases relatively small amount of energy / little energy
心的坚强决定了我们的命运。当
lost as heat; Releases energy instantaneously; Phosphorylates other compounds, making them
more reactive; Can be rapidly re-synthesised; Does not leave cells;
我们面对挫折时，是一颗不屈的
心让我们勇敢前行
ATP Structure vs DNA Nucleotide - (ANSWER)ATP has ribose and DNA has deoxyribose;
ATP has 3 phosphates and DNA nucleotide has one phosphate; Base is always adenine in ATP
and bases vary in DNA nucleotide (A,C,G or T);
Water Properties - (ANSWER)A metabolite in
condensation/hydrolysis/photosynthesis/respiration; A solvent so (metabolic) reactions can
occur; High heat capacity so buffers changes in temperature; Large latent heat of vaporisation so
provides a cooling effect (through evaporation); Cohesion (between water molecules) so supports
columns of water (in plants); Cohesion (between water molecules) so produces surface tension
supporting organisms;
High heat capacity - (ANSWER)Buffers temperature changes in biological systems.
Latent heat of vaporisation - (ANSWER)Cooling effect through evaporation of water.
