IB DP Biology Mock Exam HL Paper 1A Set 3 - 2025 Syllabus

IB DP Biology Mock Exam HL Paper 1A Set 3

Prepare for the IB DP Biology Exam with our comprehensive IB DP Biology Exam Mock Exam HL Paper 1A Set 3. Test your knowledge and understanding of key concepts with challenging questions covering all essential topics. Identify areas for improvement and boost your confidence for the real exam

IB DP Biology Mock Tests -All Sets

Question

What occurs during translation?

I. Polypeptides synthesised on ribosomes
II. RNA polymerase catalyses polypeptide synthesis
III. Complementary base pairing between codons and anticodons

(A) I and II only
(B) I and III only
(C) II and III only
(D) I, II and III

▶️ Answer/Explanation

Translation occurs on ribosomes where a polypeptide is synthesized (statement I). tRNA anticodons pair complementarily with mRNA codons to specify amino acids (statement III). RNA polymerase functions in transcription, not translation, so statement II is incorrect.
✅ Answer: (B)

Question

The graph below represents changes in membrane potential during an action potential in a neuron.

During which phase on the graph do voltage-gated sodium channels open, leading to rapid depolarization of the neuron’s membrane?

A. At \( 1 \)
B. Between \( 1 \) and \( 2 \)
C. At \( 2 \)
D. Between \( 2 \) and \( 3 \)

▶️ Answer/Explanation

Voltage-gated sodium (\(\text{Na}^+\)) channels open at the start of depolarization, allowing sodium ions to flow rapidly into the neuron.

This occurs between points \( 1 \) and \( 2 \) on the graph, where the membrane potential rises sharply from its resting potential of approximately \( -70~\text{mV} \) toward positive values, peaking around \( +40~\text{mV} \).

✅ Answer: (B) Between \( 1 \) and \( 2 \)

IB DP Biology Mock Exam HL Paper 1A Set 3 - 2025 Syllabus