IB DP Biology- D1.2 Protein synthesis -FA 2025- IB Style Questions For HL Paper 2

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Question

Which statement distinguishes between the roles of free and bound ribosomes?

A. Free ribosomes synthesize proteins for use inside the cell, whereas bound ribosomes synthesize proteins mainly for export.

B. Free ribosomes synthesize proteins mainly for export, whereas bound ribosomes synthesize proteins for use inside the cell.

C. Free ribosomes synthesize proteins, whereas bound ribosomes do not.

D. Bound ribosomes synthesize proteins, whereas free ribosomes do not.

▶️Answer/Explanation

Ans: A

Question

The sequence of bases on a short section of the antisense strand of a gene undergoing transcription is shown:

What is the sequence of bases on the resulting mRNA?

A. 3′ CATG 5′

B. 5′ GUAC 3′

C. 3′ GUAC 5′

D. 3′ GTAC 5′

▶️Answer/Explanation

Ans: C

Question

b.i. State one role of nucleosomes in eukaryotic cells.[1]

b.ii. Outline how Hershey and Chase’s experiment provided evidence for DNA as the genetic material. [3]

b.iii. State one function for a region of DNA that does not code for proteins. [1]

c.i. Outline the role of the A-site of ribosomes in translation. [1]

c.ii. Outline the role of tRNA activating enzymes in translation. [2]

▶️Answer/Explanation

Markscheme

a. help to supercoil/pack DNA in chromosomes
b. help to regulate transcription / gene expression

b.i.

a. experiment is meant to determine whether DNA or protein is the genetic material
b. viruses/bacteriophages grown in radioactive S/S³⁵ which enters the protein coat

c. viruses/bacteriophages grown in radioactive P/P³² which enters the DNA

d. «radioactive» viral DNA entered the bacterial cell during infection
OR
«radioactive» viral protein did not enter the bacterial cell during infection

b.ii.

regulator of gene expression/introns/telomeres/genes for tRNA / rRNA / promoter / enhancer / silencer / site for primer to bind / codes for mRNA primer

b.iii.

binding/entry of tRNA carrying amino acids/aminoacyl tRNA / charged tRNA / site of transfer of growing polypeptide chains/peptide bond formation

c.i.

a. ATP «hydrolysis» provides energy for amino acid attachment ✔
b. they attach a specific amino acid to the (3′) end / free CCA of a tRNA ✔

c. they do this repeatedly / they attach amino acid to all of the tRNA molecules that have anticodon corresponding to that amino acid

c.ii.

IB DP Biology- D1.2 Protein synthesis -FA 2025- IB Style Questions For HL Paper 2

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