AQA AS Level Biology Paper 2, June 2023: Question 1

5 marks · Medium difficulty · Short Answer

Identify the correct function of ribosomes, name two biological molecules coded for by genes excluding proteins, and use data on phospholipid percentages to explain the structural and functional differences between rough and smooth endoplasmic reticulum.

Practise this question

Question

Three-part biology exam question. Question 01.1 asks to tick the correct statement about the function of ribosomes from four multiple-choice options (1 mark). Question 01.2 asks to name two biological molecules coded for by a gene, excluding polypeptides or proteins (1 mark). Question 01.3 presents Table 1 showing the percentage of phospholipids in rough endoplasmic reticulum (46.8%) and smooth endoplasmic reticulum (52.5%), and asks to use the data to suggest how their structures and functions differ (3 marks).
Question text

01.1 Which statement about the function of ribosomes is correct?

Tick ( ) one box.

[1 mark]

Site of transcription, catalyse the joining of amino acids by hydrolysis

reactions

Site of transcription, catalyse the joining of nucleotides by

condensation reactions

Site of translation, catalyse the joining of amino acids by

condensation reactions

Site of translation, catalyse the joining of nucleotides by hydrolysis

reactions

01.2 Name two biological molecules that can be coded for by a gene.

Do not include a polypeptide or protein in your answer.

[1 mark]

01.3 Scientists investigated the structure of the endoplasmic reticulum.

Table 1 shows some of the scientists’ results.

Table 1

Percentage of endoplasmic

Type of endoplasmic reticulum

reticulum made of phospholipids

Rough 46.8

Smooth 52.5

Use the data in Table 1 to suggest how the structure of rough endoplasmic reticulum

is different from the structure of smooth endoplasmic reticulum and how this is

related to their functions.

[3 marks]

Mark scheme

Show the mark scheme Mark scheme showing acceptable answers for questions 01.1, 01.2, and 01.3. For 01.1, the correct answer is 'Site of translation, catalyse the joining of amino acids by condensation reactions'. For 01.2, any two from rRNA, (pre)mRNA, or tRNA. For 01.3, marking points include referencing lower phospholipid percentage or higher protein/ribosome presence in rough ER, linking rough ER to protein production/transport, and smooth ER to lipid production/transport.

Question Marking Guidance Mark Comments

Site of translation, catalyse the joining of amino 1

01.1 acids by condensation reactions;

(AO1)

Any two from:

rRNA; 1 max Ignore capitalization

01.2

(Pre) mRNA; (AO1) of r, m and t

tRNA;

1. Less phospholipids in rough

1. Accept references

OR to percentages from

More protein/glycoprotein in rough Table 1.

OR

Presence of ribosomes in rough; 3

2. (More protein/glycoprotein/ribosomes) (2 x 2.Accept

01.3 Rough – production/transport of proteins;

AO2, 1 modifies/packages

3. (More phospholipid) x AO3) proteins

Smooth –

production/modification/packaging/transport of 3.Accept

lipids; storage/synthesis of

carbohydrates

3. Accept storage of

lipds

How to answer it

Ribosomes, Gene Products, and Endoplasmic Reticulum Structure

What this question tests

This revision guide covers core cell ultrastructure and protein synthesis concepts. It tests your knowledge of organelle functions (ribosomes vs. transcription sites), non-polypeptide products of gene expression (types of RNA), and your ability to interpret quantitative data comparing rough and smooth endoplasmic reticulum structures in relation to their specific cellular roles.

Question 01.1 — Function of Ribosomes

Which statement about the function of ribosomes is correct?

✅ Correct Answer

Site of translation, catalyse the joining of amino acids by condensation reactions.

1 mark (AO1)

💡 Key Knowledge

  • Translation vs Transcription: Transcription occurs in the nucleus (making pre-mRNA/mRNA). Translation occurs at the ribosome in the cytoplasm or RER.
  • Bond Formation: Ribosomes facilitate peptide bond formation between amino acids, releasing a molecule of water per bond (condensation).

❌ Common Errors

Students frequently confuse transcription (nucleus/DNA to mRNA) with translation (ribosome/mRNA to polypeptide). Others incorrectly state that ribosomes use hydrolysis reactions rather than condensation to join monomers.

Question 01.2 — Products of Genes

Name two biological molecules that can be coded for by a gene (excluding polypeptides/proteins).

✅ Correct Answer (Any two)

  • rRNA (Ribosomal RNA)
  • mRNA (Messenger RNA / pre-mRNA)
  • tRNA (Transfer RNA)
1 max mark (AO1) — Ignore capitalisation of r, m, and t prefixes.

🧠 Exam Technique

Read the negative constraint carefully: "Do not include a polypeptide or protein". Because genes code for RNA molecules that are not always translated into proteins (such as structural rRNA or adapter tRNA), these are valid alternative gene products.

Question 01.3 — Endoplasmic Reticulum Data Analysis

Use the data in Table 1 to suggest how the structure of rough endoplasmic reticulum is different from smooth endoplasmic reticulum and how this relates to their functions.

✅ Correct Mark Scheme Points (3 marks total)

  • Point 1 (Structural difference): Less phospholipid in rough ER (46.8%) compared to smooth ER (52.5%), OR rough ER has more protein/glycoprotein/ribosomes.
  • Point 2 (RER Function): More protein/glycoproteins/ribosomes means rough ER is adapted for the production, modification, and transport of proteins.
  • Point 3 (SER Function): More phospholipid means smooth ER is adapted for the production, modification, packaging, and transport of lipids/carbohydrates.
3 marks breakdown: 2 × AO2 (Applying data to structure), 1 × AO3 (Linking structure to function).

🧠 Exam Technique & Examiner Commentary

Top-level responses explicitly paired the quantitative data difference (e.g., lower phospholipid percentage in RER) directly with the presence of ribosomes and proteins, then correctly assigned the distinct metabolic roles of lipid synthesis (SER) versus protein synthesis (RER).

Topics

Biology · 3.1 Biological molecules · 3.2 Cells · 3.4 Genetic information, variation and relationships between organisms

Question and mark scheme from the AQA AS Level Biology examination, Paper 2, June 2023. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.