Noesis
Level 1 — RecognitionBiomolecules — Proteins & Nucleic Acids

Biomolecules — Proteins & Nucleic Acids

⏱ 20 minutes30 marksprintable — key stays hidden on paper

Level 1 Test — Recognition

Time limit: 20 minutes Total marks: 30

Section A — Multiple Choice (1 mark each) [10 marks]

Q1. Which four elements are ALWAYS present in every protein?

  • A) C, H, O, P
  • B) C, H, O, N
  • C) C, H, N, S
  • D) C, O, N, P

Q2. The general structure of an amino acid contains a central carbon bonded to all of the following EXCEPT:

  • A) an amino group (–NH₂)
  • B) a carboxyl group (–COOH)
  • C) a phosphate group (–PO₄)
  • D) a hydrogen atom and an R group

Q3. A peptide bond forms between which two groups of adjacent amino acids?

  • A) amino group and R group
  • B) carboxyl group of one and amino group of the next
  • C) two R groups
  • D) two carboxyl groups

Q4. During peptide bond formation, which molecule is released?

  • A) carbon dioxide
  • B) ammonia
  • C) water
  • D) oxygen

Q5. The alpha helix and beta pleated sheet are examples of which level of protein structure?

  • A) primary
  • B) secondary
  • C) tertiary
  • D) quaternary

Q6. Which nitrogenous bases are purines?

  • A) cytosine and thymine
  • B) adenine and guanine
  • C) uracil and cytosine
  • D) thymine and uracil

Q7. Which sugar is found in RNA?

  • A) deoxyribose
  • B) glucose
  • C) ribose
  • D) fructose

Q8. In DNA, adenine pairs with:

  • A) guanine
  • B) cytosine
  • C) thymine
  • D) uracil

Q9. ATP releases energy when it is hydrolysed to:

  • A) ADP + inorganic phosphate
  • B) AMP + ribose
  • C) adenine + phosphate
  • D) two ADP molecules

Q10. Which food test uses a blue reagent that turns violet/purple in the presence of protein?

  • A) Benedict's
  • B) iodine
  • C) Biuret
  • D) Sudan III

Section B — Matching (1 mark each) [6 marks]

Q11. Match each food test (i–iv) to the biomolecule it detects, and the two remaining functions (v–vi) to their protein type.

Column A Column B
(i) Benedict's (a) starch
(ii) Iodine (b) lipid
(iii) Biuret (c) reducing sugar
(iv) Sudan III (d) protein
(v) Haemoglobin (e) enzyme (catalytic protein)
(vi) Amylase (f) transport protein

Section C — True or False WITH Justification (2 marks each) [14 marks]

(1 mark for correct T/F, 1 mark for correct justification)

Q12. DNA is normally double-stranded while RNA is normally single-stranded.

Q13. Denaturation of a protein breaks its peptide bonds and destroys the primary structure.

Q14. The sequence of amino acids in a polypeptide is called the primary structure.

Q15. Nucleotides contain a sugar, a phosphate group, and a nitrogenous base.

Q16. In RNA, thymine replaces uracil.

Q17. Quaternary structure exists in all proteins.

Q18. ATP is described as the "energy currency" of the cell because it stores and transfers energy for cellular processes.

End of paper

Answer keyMark scheme & solutions

Section A (1 mark each)

Q1. B — Proteins always contain Carbon, Hydrogen, Oxygen and Nitrogen (N distinguishes them from carbohydrates/lipids). Sulfur is present only in some. (1)

Q2. C — The general amino acid has central C bonded to –NH₂, –COOH, –H and –R. Phosphate is not part of an amino acid. (1)

Q3. B — Peptide bond = between the carboxyl (–COOH) of one amino acid and amino (–NH₂) of the next. (1)

Q4. C — Condensation reaction releases water. (1)

Q5. B — Alpha helix and beta sheet arise from H-bonding in the backbone = secondary structure. (1)

Q6. B — Purines (double ring) = adenine and guanine. (1)

Q7. C — RNA contains ribose; DNA contains deoxyribose. (1)

Q8. C — A pairs with thymine (2 H-bonds) in DNA. (1)

Q9. A — ATP → ADP + Pi releases usable energy. (1)

Q10. C — Biuret reagent (blue) turns violet/purple with protein (peptide bonds). (1)

Section B (1 mark each)

Q11.

  • (i) Benedict's → (c) reducing sugar
  • (ii) Iodine → (a) starch
  • (iii) Biuret → (d) protein
  • (iv) Sudan III → (b) lipid
  • (v) Haemoglobin → (f) transport protein
  • (vi) Amylase → (e) enzyme (catalytic protein)

(1 mark each correct pairing, total 6)

Section C (2 marks each: 1 T/F + 1 justification)

Q12. TRUE (1) — DNA forms a double helix of two complementary strands; RNA (mRNA/tRNA/rRNA) is typically a single strand. (1)

Q13. FALSE (1) — Denaturation breaks the weaker bonds (H-bonds, ionic, disulfide interactions) that maintain secondary, tertiary and quaternary shape; peptide bonds and the primary sequence remain intact. (1)

Q14. TRUE (1) — Primary structure = the specific linear order/sequence of amino acids joined by peptide bonds. (1)

Q15. TRUE (1) — Every nucleotide = pentose sugar + phosphate group + nitrogenous base. (1)

Q16. FALSE (1) — It is the reverse: in RNA uracil replaces thymine; thymine is found in DNA. (1)

Q17. FALSE (1) — Quaternary structure exists only in proteins with two or more polypeptide chains (e.g. haemoglobin); single-chain proteins have no quaternary level. (1)

Q18. TRUE (1) — Hydrolysis of ATP to ADP + Pi releases energy that powers cellular work; ATP is continually regenerated, so it acts as a transferable energy currency. (1)

Mark distribution check

Section A = 10, Section B = 6, Section C = 7 × 2 = 14. Total = 30.

[
  {"claim":"Section A has 10 one-mark questions totalling 10 marks","code":"result = (10*1 == 10)"},
  {"claim":"Section B has 6 matching items at 1 mark = 6 marks","code":"result = (6*1 == 6)"},
  {"claim":"Section C has 7 questions at 2 marks = 14 marks","code":"result = (7*2 == 14)"},
  {"claim":"Total paper marks equal 30","code":"secA=10; secB=6; secC=7*2; result = (secA+secB+secC == 30)"}
]