IB Biology HL 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
Multiple choiceWritten
Difficulty
EasyMediumHard

Question 1

Paper 2Easy6 marks

During aerobic respiration, electrons pass along the electron transport chain in the inner mitochondrial membrane. Answer the following questions about the proton gradient and ATP synthesis.

(a)

State how energy released as electrons pass along the electron transport chain is used, and state the direction in which protons are moved across the inner mitochondrial membrane.

[2]
(b)

State the difference in proton concentration across the inner mitochondrial membrane that results.

[1]
(c)

State the direction in which protons move through ATP synthase.

[1]
(d)

Explain how the movement of protons through ATP synthase results in ATP synthesis.

[2]

Question 2

Multiple choiceEasy1 mark

Equal amounts of GP were added to four reaction mixtures. ATP and reduced NADP were added as indicated; all other conditions and the time interval were identical. The amount of TP formed after 1 min was measured.

MixtureATP addedReduced NADP addedTP formed / μmol
1YesNo0.0
2NoYes0.0
3YesYes2.4
4NoNo0.0

Which combination was present in the mixture that formed TP?

Show answer and explanation

Answer: C. Only mixture 3 formed TP, and it contained both ATP and reduced NADP. This matches the conversion of GP into TP, which uses ATP and reduced NADP.

A: assumes ATP alone is sufficient; mixture 1 formed no TP. B: assumes reduced NADP alone is sufficient; mixture 2 formed no TP. D: selects the mixture without either compound, which formed no TP.

Remember: GP conversion to TP requires both ATP and reduced NADP.

Question 3

Paper 2Easy5 marks

During a simplified accounting of the Calvin cycle in a leaf, six molecules of triose phosphate are produced. One molecule leaves as net product; the remainder is used to regenerate RuBP.

(a)

Determine the number and fraction of the triose phosphate molecules used to regenerate RuBP.

[2]
(b)

State the number of RuBP molecules regenerated from these five triose phosphate molecules.

[1]
(c)

Explain the role of ATP in RuBP regeneration and why regenerated RuBP is needed for the Calvin cycle to continue.

[2]

Question 4

Multiple choiceEasy1 mark

A hospital restricts antibiotics to cases in which they are needed. Some pathogenic bacterial strains are already resistant to several antibiotics. How can this careful use slow the increase of multiresistant strains?

Show answer and explanation

Answer: D. Antibiotic use selects for resistant bacteria because susceptible bacteria are more likely to be killed. With less unnecessary antibiotic use, the selective advantage of multiresistant bacteria is reduced, slowing their increase in frequency.

A: Treats antibiotics as directly causing resistance mutations rather than selecting bacteria that already have resistance.
B: Confuses reduced selection with blocked inheritance; resistant bacteria can still pass resistance to offspring.
C: Assumes resistance disappears without antibiotics; reduced use does not itself remove resistance.
Remember: antibiotics select among bacterial variants; they do not direct bacteria to become resistant.

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