A Level Biology (A2) chapter 4: Control and coordination MCQs with answers
By Team Megalecture · Updated 4 Nov 2026
55 exam-style questions on Control and coordination, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.
Ten Control and coordination questions with answers
Try each one, then open the answer. These ten stay the same; the test draws new ones every time.
1. How does auxin cause cells in a shoot to elongate?
A
it stimulates pumping of protons into the cytoplasm, which raises the pH of the cell wall and loosens it
B
it stimulates proton pumping into the cell wall, and the low pH activates expansins that loosen it
C
it breaks down all the cellulose so that the cell wall is removed
D
it makes the cell wall more rigid by adding lignin
Show answer
Answer: B. Auxin causes protons to be pumped from the cytoplasm into the cell wall. The lower pH activates expansins, which loosen the links between cellulose microfibrils, so the wall stretches as water enters by osmosis.
2. Which changes are seen in a sarcomere when a muscle contracts?
A
the A band shortens, but the I band and H zone stay the same length
B
all the bands shorten by the same amount
C
the A band stays the same, but the I band and H zone shorten
D
the H zone lengthens and the I band shortens
Show answer
Answer: C. The filaments themselves do not shorten; they slide past each other. The A band (the length of the myosin filaments) is unchanged, while the regions without overlap, the I band and H zone, get shorter.
3. In a germinating barley seed, which describes the role of gibberellin?
A
the embryo produces amylase, which causes the aleurone layer to make gibberellin
B
the aleurone layer produces gibberellin, which causes the embryo to make amylase
C
the endosperm produces gibberellin, which converts starch directly into maltose
D
the embryo produces gibberellin, which causes the aleurone layer to make amylase
Show answer
Answer: D. After the seed takes up water, the embryo releases gibberellin, which diffuses to the aleurone layer and switches on the synthesis of amylase. Amylase then hydrolyses starch in the endosperm.
4. Which describes the importance of the refractory period?
A
it keeps impulses moving one way and limits how often they can occur
B
it allows action potentials to merge into one long impulse
C
it makes each action potential larger when the stimulus is stronger
D
it allows impulses to travel in both directions along the axon at once
Show answer
Answer: A. The region just behind an action potential cannot be depolarised again at once, so the impulse moves forward only, action potentials stay separate, and there is a maximum frequency.
5. A stronger stimulus is applied to a receptor. How do the impulses in the sensory neurone change?
A
the action potentials become larger in amplitude
B
the frequency of action potentials increases
C
the action potentials travel faster along the axon
D
each action potential lasts for a longer time
Show answer
Answer: B. Action potentials are all-or-nothing, so in a given neurone they are always the same size and speed. A stronger stimulus gives a larger receptor potential, which produces action potentials more often.
6. Some hours after death, muscles become stiff (rigor mortis). Which statement explains this?
A
all the calcium ions are pumped back into the sarcoplasmic reticulum
B
ATP is no longer made, so myosin heads cannot detach from actin
C
tropomyosin moves back to cover all the myosin-binding sites on actin
D
the actin filaments are broken down by enzymes
Show answer
Answer: B. Myosin heads need ATP to release from actin. When ATP runs out, the cross-bridges stay locked in place and the muscle stays rigid.
7. How is the rapid closure of a Venus fly trap achieved?
A
auxin travels from the hairs to the midrib, where it causes the cells on the outer surface to grow
B
the lobes lose water by transpiration, so the leaf collapses shut
C
the hairs contract like muscle fibres and pull the lobes together
D
action potentials cross the lobes, and rapid water movement flips them from convex to concave
Show answer
Answer: D. Stimulating the hairs produces action potentials that travel across the lobes. Rapid movements of ions and water change the turgor of cells in the lobes, so each lobe suddenly flips from curving outwards to curving inwards, snapping the trap shut. Auxin is not involved, and hormone-driven growth would be far too slow to shut the trap in a fraction of a second.
8. In a chemoreceptor cell of a taste bud that detects salt, what causes the receptor potential?
A
Na+ being actively pumped out of the cell by the sodium–potassium pump
B
Na+ diffusing into the cell through channels in its membrane
C
K+ diffusing into the cell through potassium ion channels in its membrane
D
Cl− being actively pumped into the cell
Show answer
Answer: B. When salt is present, Na+ diffuses into the receptor cell through sodium ion channels, making the inside less negative: this depolarisation is the receptor potential.
9. What is the advantage to a Venus fly trap of closing only after two stimulations within a short time?
A
it gives small insects time to escape before the trap closes on them
B
it avoids wasting energy by closing on raindrops or debris
C
it allows the trap to catch and digest two insects at the same time
D
it allows the sensory hairs to grow back between the two stimulations
Show answer
Answer: B. A single touch may be caused by something that is not prey. Needing two touches close together makes it likely that a moving insect is present, so energy is not wasted on false closures.
10. Which is a feature of the nervous system but not of the endocrine system?
A
it carries chemical messages dissolved in the blood plasma to all parts of the body
B
it usually produces slow responses that last for a long time after the stimulus
C
it transmits electrical impulses, usually with rapid, short-lived effects
D
it uses hormones secreted by ductless glands
Show answer
Answer: C. Nerve impulses travel quickly along neurones to specific cells, and their effects are usually rapid and brief. Hormones travel in the blood and usually act more slowly and for longer.
55, each with the answer and a short explanation, across 2 topics: Control and coordination in mammals, Control and coordination in plants. Every chapter test draws ten of them, so you can take it many times.
Is the A Level Biology (A2) chapter 4 test free?
Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.
How is the chapter test marked?
The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.
