A-Level Biology 5-6 Markers
Explain how microorganisms in the soil produce a source of nitrates from the remains of crop
plants - correct answer-1) Protein/amino acids/DNA, into ammonium compounds/ ammonia
2) By saprobionts
3) Ammonium/ammonia into nitrite
4) Nitrite into nitrate
5) By nitrifying bacteria
6) Nitrogen to ammonium/ ammonia
7) By nitrogen-fixing bacteria in soil
Describe advantages and disadvantages of using chemical pesticides to control pests of
crops - correct answer-(Advantages)
1) Acts quickly
2) Can apply to particular area
3) Kills wide variety of plants
(Disadvantages)
4) Needs to be reapplied
5) Not specific
6) Pests can develop resistance
7) (Bio)accumulation
IGNORE ref. to leaching/eutrophication
Describe how plants use light energy in the light-dependent reaction - correct answer-1)
Excites electrons/ removes electrons from chlorophyll
2) Electrons move along carriers/ electron transfer chain, releasing energy
3) Energy used to join ADP and Pi to form ATP
4) Photolysis of water produces protons, electrons and oxygen
5) NADP reduced by electrons/electrons and protons/ hydrogen
Describe competitive and non-competitive inhibition of an enzyme - correct answer-1)
Inhibitors reduce binding of enzyme to substrate
(Competitive)
2) Inhibitor similar tertiary structure to substrate
3) Binds to active site
4) Inhibition can be overcome by more substrate added
(Non-competitive)
5) Inhibitor binds to side other than active site (allosteric) on enzyme
6) Changes shape of active site
7) Cannot be overcome by adding more substrate
Explain why maltase:
, - only breaks down maltose
- allows this reaction to take place at normal body temperature - correct answer-1) *Tertiary*
structure of enzyme (means)
2) Active site is complementary to maltose
3) Description of *induced fit*
4) Enzyme is a catalyst
5) Lowers activation energy required
6) By forming enzyme-substrate complexes
Explain how the diet of a person can increase the risk of coronary heart disease - correct
answer-1) Too much saturated fat/ cholesterol in diet
2) Increase in cholesterol in blood
3) Atheroma plaques in artery walls
4) Reduces diameter of *coronary* arteries
5) Less oxygen/glucose to heart tissue
6) Increase in blood pressure
7) (Increased risk of) clot/ thrombosis/ embolism/ aneurysm
Describe how the heart controls and coordinates the regular contraction of the atria and
ventricles - correct answer-1) SAN -> AVN -> bundle of His
2) Impulses/ electrical activity (over atria)
3) Atria contract
4) Non-conduction tissue (between atria and ventricles)
5) Delay (at AVN) ensures atria empty before ventricles contract
6) Ventricles contract from apex upwards
Describe the processes involved in the absorption of the products of starch digestion -
correct answer-1) Glucose moves in with sodium (into epithelial cell)
2) Via. (carrier/channel) protein
3) Sodium removed (from epithelial cell) by active transport
4) Into blood
5) Maintaining low sodium concentration (in epithelial cell)/ sodium concentration gradient
(between lumen and epithelial cell)
6) Glucose moves into blood
7) By (facilitated) diffusion
Describe the role of the enzymes of the digestive system in the complete breakdown if starch
- correct answer-1) Amylase
2) (Starch) to maltose
3) Maltase
4) Maltose to glucose
5) Hydrolysis
6) Of glycosidic bonds
Explain how the epithelial cells that line the small intestine are adapted for absorption of
glucose - correct answer-1) Microvilli
Explain how microorganisms in the soil produce a source of nitrates from the remains of crop
plants - correct answer-1) Protein/amino acids/DNA, into ammonium compounds/ ammonia
2) By saprobionts
3) Ammonium/ammonia into nitrite
4) Nitrite into nitrate
5) By nitrifying bacteria
6) Nitrogen to ammonium/ ammonia
7) By nitrogen-fixing bacteria in soil
Describe advantages and disadvantages of using chemical pesticides to control pests of
crops - correct answer-(Advantages)
1) Acts quickly
2) Can apply to particular area
3) Kills wide variety of plants
(Disadvantages)
4) Needs to be reapplied
5) Not specific
6) Pests can develop resistance
7) (Bio)accumulation
IGNORE ref. to leaching/eutrophication
Describe how plants use light energy in the light-dependent reaction - correct answer-1)
Excites electrons/ removes electrons from chlorophyll
2) Electrons move along carriers/ electron transfer chain, releasing energy
3) Energy used to join ADP and Pi to form ATP
4) Photolysis of water produces protons, electrons and oxygen
5) NADP reduced by electrons/electrons and protons/ hydrogen
Describe competitive and non-competitive inhibition of an enzyme - correct answer-1)
Inhibitors reduce binding of enzyme to substrate
(Competitive)
2) Inhibitor similar tertiary structure to substrate
3) Binds to active site
4) Inhibition can be overcome by more substrate added
(Non-competitive)
5) Inhibitor binds to side other than active site (allosteric) on enzyme
6) Changes shape of active site
7) Cannot be overcome by adding more substrate
Explain why maltase:
, - only breaks down maltose
- allows this reaction to take place at normal body temperature - correct answer-1) *Tertiary*
structure of enzyme (means)
2) Active site is complementary to maltose
3) Description of *induced fit*
4) Enzyme is a catalyst
5) Lowers activation energy required
6) By forming enzyme-substrate complexes
Explain how the diet of a person can increase the risk of coronary heart disease - correct
answer-1) Too much saturated fat/ cholesterol in diet
2) Increase in cholesterol in blood
3) Atheroma plaques in artery walls
4) Reduces diameter of *coronary* arteries
5) Less oxygen/glucose to heart tissue
6) Increase in blood pressure
7) (Increased risk of) clot/ thrombosis/ embolism/ aneurysm
Describe how the heart controls and coordinates the regular contraction of the atria and
ventricles - correct answer-1) SAN -> AVN -> bundle of His
2) Impulses/ electrical activity (over atria)
3) Atria contract
4) Non-conduction tissue (between atria and ventricles)
5) Delay (at AVN) ensures atria empty before ventricles contract
6) Ventricles contract from apex upwards
Describe the processes involved in the absorption of the products of starch digestion -
correct answer-1) Glucose moves in with sodium (into epithelial cell)
2) Via. (carrier/channel) protein
3) Sodium removed (from epithelial cell) by active transport
4) Into blood
5) Maintaining low sodium concentration (in epithelial cell)/ sodium concentration gradient
(between lumen and epithelial cell)
6) Glucose moves into blood
7) By (facilitated) diffusion
Describe the role of the enzymes of the digestive system in the complete breakdown if starch
- correct answer-1) Amylase
2) (Starch) to maltose
3) Maltase
4) Maltose to glucose
5) Hydrolysis
6) Of glycosidic bonds
Explain how the epithelial cells that line the small intestine are adapted for absorption of
glucose - correct answer-1) Microvilli
