IB Biology SL Theme C: Interaction and interdependence questions

Exam-style multiple choice and written questions with full markschemes. Check multiple choice answers straight away, or type, photograph or draw a written answer and get it marked.

Type
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Question 1

Multiple choiceEasy1 mark

A cell’s metabolic reactions must occur quickly enough to support its activities. Which role of enzymes provides this benefit?

Show answer and explanation

Answer: D. Enzymes are catalysts that increase the rates of reactions. Faster metabolic reactions can support the activities of the cell.

A: confuses catalysis with increasing the supply of reactants. B: treats enzymes as an energy source rather than catalysts. C: treats enzymes as reactants that are converted into products.

Remember: enzymes increase reaction rates without being used up.

Question 2

Multiple choiceEasy1 mark

When an impulse reaches a neuron terminal, the presynaptic membrane depolarizes and neurotransmitter is released. Which ion movement acts as the intracellular signal for this release?

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Answer: C. Depolarization of the presynaptic membrane causes Ca²⁺ uptake into the neuron. Ca²⁺ acts as a signalling chemical inside the neuron and promotes neurotransmitter release. A: confuses K⁺ efflux, associated with repolarization, with the signal for neurotransmitter release. B: confuses Na⁺ influx, associated with depolarization, with the ion that signals release. D: reverses the direction: Ca²⁺ enters rather than leaves the presynaptic neuron. Remember: Ca²⁺ entry at the presynaptic membrane signals neurotransmitter release.

Question 3

Paper 2Easy5 marks

A healthy adult’s pineal gland secretes melatonin. The table shows relative melatonin secretion over 24 hours. A student walks along a narrow beam while catching a ball.

TimeRelative melatonin secretion / arbitrary units
08:002
14:001
20:005
02:009
08:00 next day2
(a)

Describe the pattern of melatonin secretion shown in the table.

[1]
(b)

Explain how this pattern helps establish a cycle of sleeping and waking.

[2]
(c)

State two roles of the cerebellum in the student’s movements.

[2]

Question 4

Multiple choiceEasy1 mark

The diagram shows the inputs used by four organisms that synthesize carbon compounds. Which organism is an autotroph?

The carbon source shown is the sole carbon-containing input.external light energyglucoseOrganism Acarbon compoundsexternal light energyamino acidsOrganism Bcarbon compoundsexternal light energycarbon dioxide (CO2)Organism Ccarbon compoundsexternal light energystarchOrganism Dcarbon compounds
Show answer and explanation

Answer: C. An autotroph uses an external energy source to synthesize carbon compounds from simple inorganic substances. Organism C receives external light energy and its sole carbon-containing input is CO₂, a simple inorganic substance.

A: treats glucose, an organic carbon source, as a simple inorganic substance.
B: treats amino acids, which are organic, as a simple inorganic carbon source.
D: treats starch, an organic carbon source, as a simple inorganic substance.
Remember: autotrophy depends on the source of carbon, not only on the energy source.

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