OCR A Level Biology Paper 1 (2022
Priority Topics) GUARANTEED GRADE
A+
Auxin is a plant hormone produced in the shoot tip. Auxin causes cell
elongation and travels down the stem from the tip. Auxin is destroyed
by sunlight. Explain how this leads to positive phototropism in the
plant.
Auxin is broken down on the sunny side of the plant. Cells on the
shaded side will elongate due to auxin, causing curvature of the stem
so that the plant grows towards the light.
Ivy plants often use walls or other plants as a support when growing.
State the type of tropism being used.
Thigmotropism
Roots grow towards the centre of gravity. State the type of tropism
this demonstrates.
Positive geotropism
A gardener decides that they would like a plant that grows as wide as
possible. Suggest and explain how they could cut the plant in order
to achieve this shape.
The gardener would need to cut off the shoot tip containing the
apical meristem. This would allow side branches to grow from lateral
buds, and so form a plant with side branches.
State the role of gibberellin.
It is a growth regulator, causing stem elongation
State the role of cytokinin
It promotes lateral bud growth
State two commercial uses of gibberellins with reference to plants.
They can be used to enhance seed germination in growing malt for beer,
and delay senescence of citrus fruits, making them available for
longer in shops.
State two commercial uses of auxins.
They can be used in rooting powder to grow roots in young plant
cuttings, and can be used as a herbicide to kill weeds.
State the different neurones located in the central and peripheral
nervous systems.
The PNS is made up of sensory and motor neurones, whereas the CNS is
mostly made up of relay neurones.
State the role of the sympathetic nervous system.
Activating the fight-or-flight response, preparing the body for
activity and stimulating effectors
, State the function of the medulla oblongata.
Controlling the involuntary/autonomic functions/responses, such as
heart rate.
State one function of the pituitary gland.
Storing and releasing hormones that regulate homeostatic mechanisms
in the body, such as thermoregulation or osmoregulation.
State two processes controlled by the hypothalamus.
Monitoring the composition of the blood plasma and hormone production.
Describe what is meant by a 'second messenger molecule'.
A signalling molecule inside a cell that is activated by a hormone
(first messenger) binding to the outside of the cell, which
stimulates a change in the activity of the cell.
Describe the basic structure of mammalian skeletal muscle.
It is made up of many smaller strands or fibres, called myofibrils.
Myofibrils are made up of many repeating units called sarcomeres.
State the name of the neurotransmitter released at the neuromuscular
junction.
Acetylcholine
Describe how actin and myosin are arranged in resting muscle.
Myosin and actin are not interlocked. Wide I-bands are present and
there are visible H-zones.
Giving an example, explain why plants need to carry out the process
of respiration.
Respiration is used to synthesise molecules of ATP, which is then
used for energy-requiring processes around the plant
State precisely where the link reaction takes place in the cell.
The mitochondrial matrix
Describe where pyruvate, which is produced in glycolysis, would move
to be used in the link reaction.
Across both the outer and inner mitochondrial membranes into the
mitochondrial matrix
Explain the term decarboxylation.
Removal of a carbon dioxide/carboxyl group
Describe what is meant by a respiratory substrate
An organic substance that can be oxidised by respiration/a molecule
used in glycolysis/the link reaction/Krebs cycle, releasing energy to
make molecules of ATP.
Describe two differences between the respiration and photosynthesis
reactions.
Respiration breaks down glucose, whereas photosynthesis produces
glucose. Respiration releases energy to use in metabolic processes,
whereas photosynthesis uses energy to fix carbon.
Chloroplasts contain a large number of ribosomes. Explain the
importance of these ribosomes.
Priority Topics) GUARANTEED GRADE
A+
Auxin is a plant hormone produced in the shoot tip. Auxin causes cell
elongation and travels down the stem from the tip. Auxin is destroyed
by sunlight. Explain how this leads to positive phototropism in the
plant.
Auxin is broken down on the sunny side of the plant. Cells on the
shaded side will elongate due to auxin, causing curvature of the stem
so that the plant grows towards the light.
Ivy plants often use walls or other plants as a support when growing.
State the type of tropism being used.
Thigmotropism
Roots grow towards the centre of gravity. State the type of tropism
this demonstrates.
Positive geotropism
A gardener decides that they would like a plant that grows as wide as
possible. Suggest and explain how they could cut the plant in order
to achieve this shape.
The gardener would need to cut off the shoot tip containing the
apical meristem. This would allow side branches to grow from lateral
buds, and so form a plant with side branches.
State the role of gibberellin.
It is a growth regulator, causing stem elongation
State the role of cytokinin
It promotes lateral bud growth
State two commercial uses of gibberellins with reference to plants.
They can be used to enhance seed germination in growing malt for beer,
and delay senescence of citrus fruits, making them available for
longer in shops.
State two commercial uses of auxins.
They can be used in rooting powder to grow roots in young plant
cuttings, and can be used as a herbicide to kill weeds.
State the different neurones located in the central and peripheral
nervous systems.
The PNS is made up of sensory and motor neurones, whereas the CNS is
mostly made up of relay neurones.
State the role of the sympathetic nervous system.
Activating the fight-or-flight response, preparing the body for
activity and stimulating effectors
, State the function of the medulla oblongata.
Controlling the involuntary/autonomic functions/responses, such as
heart rate.
State one function of the pituitary gland.
Storing and releasing hormones that regulate homeostatic mechanisms
in the body, such as thermoregulation or osmoregulation.
State two processes controlled by the hypothalamus.
Monitoring the composition of the blood plasma and hormone production.
Describe what is meant by a 'second messenger molecule'.
A signalling molecule inside a cell that is activated by a hormone
(first messenger) binding to the outside of the cell, which
stimulates a change in the activity of the cell.
Describe the basic structure of mammalian skeletal muscle.
It is made up of many smaller strands or fibres, called myofibrils.
Myofibrils are made up of many repeating units called sarcomeres.
State the name of the neurotransmitter released at the neuromuscular
junction.
Acetylcholine
Describe how actin and myosin are arranged in resting muscle.
Myosin and actin are not interlocked. Wide I-bands are present and
there are visible H-zones.
Giving an example, explain why plants need to carry out the process
of respiration.
Respiration is used to synthesise molecules of ATP, which is then
used for energy-requiring processes around the plant
State precisely where the link reaction takes place in the cell.
The mitochondrial matrix
Describe where pyruvate, which is produced in glycolysis, would move
to be used in the link reaction.
Across both the outer and inner mitochondrial membranes into the
mitochondrial matrix
Explain the term decarboxylation.
Removal of a carbon dioxide/carboxyl group
Describe what is meant by a respiratory substrate
An organic substance that can be oxidised by respiration/a molecule
used in glycolysis/the link reaction/Krebs cycle, releasing energy to
make molecules of ATP.
Describe two differences between the respiration and photosynthesis
reactions.
Respiration breaks down glucose, whereas photosynthesis produces
glucose. Respiration releases energy to use in metabolic processes,
whereas photosynthesis uses energy to fix carbon.
Chloroplasts contain a large number of ribosomes. Explain the
importance of these ribosomes.
