AQA BIOLOGY 2025 — PAPER 1 EXAM QUESTIONS
Topics: Biological Molecules, Cells, Transport, Cell Division,
Exchange Surfaces
SECTION A: MULTIPLE CHOICE QUESTIONS (Questions 1–50)
1. Which monosaccharide is a product of starch hydrolysis?
A. Fructose
B. Galactose
C. Glucose (correct answer)
D. Ribose
Rationale: Starch is a polysaccharide composed of glucose monomers.
Hydrolysis breaks glycosidic bonds, releasing glucose units.
2. The bond formed between two amino acids during condensation is
called:
A. A glycosidic bond
B. An ester bond
C. A peptide bond (correct answer)
D. A phosphodiester bond
Rationale: A peptide bond forms between the carboxyl group of one amino acid
and the amino group of another, with the loss of a water molecule.
3. Which test is used to identify the presence of reducing sugars?
A. Biuret test
B. Benedict’s test (correct answer)
C. Emulsion test
D. Iodine test
Generated by Kimi.ai
,Rationale: Benedict’s test uses copper(II) sulfate in alkaline conditions; reducing
sugars reduce Cu²⁺ to Cu⁺, producing a brick-red precipitate.
4. A triglyceride is formed from:
A. One glycerol and three fatty acids (correct answer)
B. Three glycerols and one fatty acid
C. One glycerol and one fatty acid
D. Two glycerols and two fatty acids
Rationale: Triglycerides consist of a glycerol backbone with three fatty acid
chains attached via ester bonds formed by condensation reactions.
5. Which of the following is a saturated fatty acid?
A. Oleic acid
B. Linoleic acid
C. Palmitic acid (correct answer)
D. Alpha-linolenic acid
Rationale: Palmitic acid has no carbon-carbon double bonds in its hydrocarbon
chain. Oleic, linoleic, and alpha-linolenic acids are unsaturated with one or more
double bonds.
6. The primary structure of a protein refers to:
A. The three-dimensional shape maintained by disulfide bridges
B. The sequence of amino acids in the polypeptide chain (correct answer)
C. The folding into alpha-helices and beta-pleated sheets
D. The association of multiple polypeptide subunits
Rationale: Primary structure is the linear sequence of amino acids joined by
peptide bonds. Secondary, tertiary, and quaternary structures involve increasing
levels of folding and association.
7. Which molecule is described as “amide”?
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,A. Triglyceride
B. Phospholipid
C. Protein (correct answer)
D. Starch
Rationale: Proteins contain peptide bonds, which are amide linkages (—CO—
NH—) formed between amino acids.
8. In a phospholipid, the phosphate group is:
A. Hydrophobic
B. Hydrophilic (correct answer)
C. Non-polar
D. Insoluble in water
Rationale: The phosphate “head” is polar and hydrophilic, while the fatty acid
“tails” are non-polar and hydrophobic, giving phospholipids their amphipathic
nature.
9. Which polysaccharide is stored in animal cells?
A. Starch
B. Cellulose
C. Glycogen (correct answer)
D. Chitin
Rationale: Glycogen is the storage polysaccharide in animals, primarily in liver
and muscle cells. Starch is plant storage; cellulose is a plant structural
polysaccharide.
10. The Biuret test detects the presence of:
A. Lipids
B. Carbohydrates
C. Proteins (correct answer)
D. Nucleic acids
Generated by Kimi.ai
, Rationale: Biuret reagent (copper sulfate in alkaline solution) reacts with peptide
bonds, producing a violet color in the presence of proteins.
11. Which enzyme catalyzes the hydrolysis of starch to maltose?
A. Lipase
B. Protease
C. Amylase (correct answer)
D. Sucrase
Rationale: Amylase (found in saliva and pancreatic juice) breaks α-1,4 glycosidic
bonds in starch, producing maltose and dextrins.
12. A competitive inhibitor of an enzyme:
A. Binds to the allosteric site
B. Binds to the active site (correct answer)
C. Changes the pH optimum
D. Denatures the enzyme permanently
Rationale: Competitive inhibitors have a similar shape to the substrate and
compete for the active site, reducing the rate of reaction. Increasing substrate
concentration can overcome this inhibition.
13. The optimum pH for pepsin is approximately:
A. 2 (correct answer)
B. 7
C. 8
D. 10
Rationale: Pepsin functions in the stomach where hydrochloric acid creates a
highly acidic environment (pH 1.5–2.5), so its optimum pH is around 2.
14. Which factor does NOT affect the rate of enzyme activity?
A. Temperature
B. pH
Generated by Kimi.ai
Topics: Biological Molecules, Cells, Transport, Cell Division,
Exchange Surfaces
SECTION A: MULTIPLE CHOICE QUESTIONS (Questions 1–50)
1. Which monosaccharide is a product of starch hydrolysis?
A. Fructose
B. Galactose
C. Glucose (correct answer)
D. Ribose
Rationale: Starch is a polysaccharide composed of glucose monomers.
Hydrolysis breaks glycosidic bonds, releasing glucose units.
2. The bond formed between two amino acids during condensation is
called:
A. A glycosidic bond
B. An ester bond
C. A peptide bond (correct answer)
D. A phosphodiester bond
Rationale: A peptide bond forms between the carboxyl group of one amino acid
and the amino group of another, with the loss of a water molecule.
3. Which test is used to identify the presence of reducing sugars?
A. Biuret test
B. Benedict’s test (correct answer)
C. Emulsion test
D. Iodine test
Generated by Kimi.ai
,Rationale: Benedict’s test uses copper(II) sulfate in alkaline conditions; reducing
sugars reduce Cu²⁺ to Cu⁺, producing a brick-red precipitate.
4. A triglyceride is formed from:
A. One glycerol and three fatty acids (correct answer)
B. Three glycerols and one fatty acid
C. One glycerol and one fatty acid
D. Two glycerols and two fatty acids
Rationale: Triglycerides consist of a glycerol backbone with three fatty acid
chains attached via ester bonds formed by condensation reactions.
5. Which of the following is a saturated fatty acid?
A. Oleic acid
B. Linoleic acid
C. Palmitic acid (correct answer)
D. Alpha-linolenic acid
Rationale: Palmitic acid has no carbon-carbon double bonds in its hydrocarbon
chain. Oleic, linoleic, and alpha-linolenic acids are unsaturated with one or more
double bonds.
6. The primary structure of a protein refers to:
A. The three-dimensional shape maintained by disulfide bridges
B. The sequence of amino acids in the polypeptide chain (correct answer)
C. The folding into alpha-helices and beta-pleated sheets
D. The association of multiple polypeptide subunits
Rationale: Primary structure is the linear sequence of amino acids joined by
peptide bonds. Secondary, tertiary, and quaternary structures involve increasing
levels of folding and association.
7. Which molecule is described as “amide”?
Generated by Kimi.ai
,A. Triglyceride
B. Phospholipid
C. Protein (correct answer)
D. Starch
Rationale: Proteins contain peptide bonds, which are amide linkages (—CO—
NH—) formed between amino acids.
8. In a phospholipid, the phosphate group is:
A. Hydrophobic
B. Hydrophilic (correct answer)
C. Non-polar
D. Insoluble in water
Rationale: The phosphate “head” is polar and hydrophilic, while the fatty acid
“tails” are non-polar and hydrophobic, giving phospholipids their amphipathic
nature.
9. Which polysaccharide is stored in animal cells?
A. Starch
B. Cellulose
C. Glycogen (correct answer)
D. Chitin
Rationale: Glycogen is the storage polysaccharide in animals, primarily in liver
and muscle cells. Starch is plant storage; cellulose is a plant structural
polysaccharide.
10. The Biuret test detects the presence of:
A. Lipids
B. Carbohydrates
C. Proteins (correct answer)
D. Nucleic acids
Generated by Kimi.ai
, Rationale: Biuret reagent (copper sulfate in alkaline solution) reacts with peptide
bonds, producing a violet color in the presence of proteins.
11. Which enzyme catalyzes the hydrolysis of starch to maltose?
A. Lipase
B. Protease
C. Amylase (correct answer)
D. Sucrase
Rationale: Amylase (found in saliva and pancreatic juice) breaks α-1,4 glycosidic
bonds in starch, producing maltose and dextrins.
12. A competitive inhibitor of an enzyme:
A. Binds to the allosteric site
B. Binds to the active site (correct answer)
C. Changes the pH optimum
D. Denatures the enzyme permanently
Rationale: Competitive inhibitors have a similar shape to the substrate and
compete for the active site, reducing the rate of reaction. Increasing substrate
concentration can overcome this inhibition.
13. The optimum pH for pepsin is approximately:
A. 2 (correct answer)
B. 7
C. 8
D. 10
Rationale: Pepsin functions in the stomach where hydrochloric acid creates a
highly acidic environment (pH 1.5–2.5), so its optimum pH is around 2.
14. Which factor does NOT affect the rate of enzyme activity?
A. Temperature
B. pH
Generated by Kimi.ai
