1
AQA A-LEVEL BIOLOGY PRACTICE EXAM 2026/2027 |
BIOLOGY | 75 VERIFIED Q&A | DETAILED RATIONALES
| PASS GUARANTEED – A+ GRADED
SECTION 1: BIOLOGICAL MOLECULES & CELLS - Questions 1-15
Q1: Water Properties
The student is reviewing biological molecules. Which property of water allows it to act as a coolant?
A. High specific heat capacity
B. High latent heat of vaporisation
C. Low density as ice
D. Cohesion
Correct Answer: B
Rationale: Water has a high latent heat of vaporisation, meaning a lot of energy is required to
convert it from liquid to gas. This makes sweating an effective cooling mechanism. High specific heat
capacity buffers temperature changes but is not directly for cooling. [100% CORRECT]
Q2: Condensation Reaction
The student is reviewing carbohydrates. Which bond is formed when two monosaccharides join?
A. Peptide bond
B. Glycosidic bond
C. Ester bond
D. Phosphodiester bond
Correct Answer: B
Rationale: A condensation reaction between two monosaccharides forms a glycosidic bond,
releasing water. Peptide bonds join amino acids. Ester bonds form in triglycerides. Phosphodiester
bonds form in nucleic acids. [100% CORRECT]
Q3: Starch vs Glycogen
The student is reviewing polysaccharides. Which statement is true of glycogen but not starch?
A. It is a polymer of α-glucose
B. It is more highly branched
C. It is found in plants
D. It is a storage polysaccharide
Correct Answer: B
,2
Rationale: Glycogen is more highly branched than starch (amylopectin), allowing rapid hydrolysis to
glucose. Both are polymers of α-glucose and storage polysaccharides, but glycogen is found in
animals. [100% CORRECT]
Q4: Triglyceride Structure
The student is reviewing lipids. A triglyceride is formed from:
A. Glycerol and three fatty acids
B. Glycerol and two fatty acids
C. Glycerol and one fatty acid
D. Three glycerols and one fatty acid
Correct Answer: A
Rationale: Triglycerides consist of one glycerol molecule and three fatty acids joined by ester bonds
formed via condensation. [100% CORRECT]
Q5: Protein Structure
The student is reviewing proteins. Which level of protein structure is determined by hydrogen bonds
between amino acids?
A. Primary
B. Secondary
C. Tertiary
D. Quaternary
Correct Answer: B
Rationale: Secondary structure (α-helix, β-pleated sheet) is maintained by hydrogen bonds between
the carboxyl group of one amino acid and the amino group of another. Primary is sequence, tertiary
is 3D folding, quaternary is multiple polypeptides. [100% CORRECT]
Q6: Enzyme Specificity
The student is reviewing enzymes. The induced-fit model explains:
A. Why enzymes are specific
B. Why enzymes lower activation energy
C. Why enzymes are affected by pH
D. Why enzymes are proteins
Correct Answer: A
Rationale: The induced-fit model states that the active site changes shape slightly to fit the
substrate, explaining specificity and how the enzyme-substrate complex forms. [100% CORRECT]
Q7: Enzyme Denaturation
, 3
The student is reviewing enzymes. Which condition causes denaturation?
A. Low temperature
B. Extreme pH
C. Optimum substrate concentration
D. Low enzyme concentration
Correct Answer: B
Rationale: Extreme pH disrupts ionic and hydrogen bonds, altering the tertiary structure and
denaturing the enzyme. Low temperature reduces activity but does not denature. [100% CORRECT]
Q8: Competitive Inhibition
The student is reviewing inhibition. A competitive inhibitor:
A. Binds to the active site
B. Binds to an allosteric site
C. Increases Vmax
D. Cannot be overcome by increasing substrate
Correct Answer: A
Rationale: Competitive inhibitors have a shape similar to the substrate and bind to the active site,
blocking substrate binding. Increasing substrate concentration can overcome it. Vmax remains
unchanged. [100% CORRECT]
Q9: DNA Structure
The student is reviewing nucleic acids. In DNA, the two strands are held together by:
A. Covalent bonds
B. Hydrogen bonds
C. Ionic bonds
D. Peptide bonds
Correct Answer: B
Rationale: Hydrogen bonds form between complementary base pairs (A-T, C-G) on opposite strands.
Covalent bonds form the sugar-phosphate backbone. [100% CORRECT]
Q10: ATP Structure
The student is reviewing ATP. ATP is a:
A. Nucleotide derivative
B. Protein
C. Carbohydrate
D. Lipid
Correct Answer: A
AQA A-LEVEL BIOLOGY PRACTICE EXAM 2026/2027 |
BIOLOGY | 75 VERIFIED Q&A | DETAILED RATIONALES
| PASS GUARANTEED – A+ GRADED
SECTION 1: BIOLOGICAL MOLECULES & CELLS - Questions 1-15
Q1: Water Properties
The student is reviewing biological molecules. Which property of water allows it to act as a coolant?
A. High specific heat capacity
B. High latent heat of vaporisation
C. Low density as ice
D. Cohesion
Correct Answer: B
Rationale: Water has a high latent heat of vaporisation, meaning a lot of energy is required to
convert it from liquid to gas. This makes sweating an effective cooling mechanism. High specific heat
capacity buffers temperature changes but is not directly for cooling. [100% CORRECT]
Q2: Condensation Reaction
The student is reviewing carbohydrates. Which bond is formed when two monosaccharides join?
A. Peptide bond
B. Glycosidic bond
C. Ester bond
D. Phosphodiester bond
Correct Answer: B
Rationale: A condensation reaction between two monosaccharides forms a glycosidic bond,
releasing water. Peptide bonds join amino acids. Ester bonds form in triglycerides. Phosphodiester
bonds form in nucleic acids. [100% CORRECT]
Q3: Starch vs Glycogen
The student is reviewing polysaccharides. Which statement is true of glycogen but not starch?
A. It is a polymer of α-glucose
B. It is more highly branched
C. It is found in plants
D. It is a storage polysaccharide
Correct Answer: B
,2
Rationale: Glycogen is more highly branched than starch (amylopectin), allowing rapid hydrolysis to
glucose. Both are polymers of α-glucose and storage polysaccharides, but glycogen is found in
animals. [100% CORRECT]
Q4: Triglyceride Structure
The student is reviewing lipids. A triglyceride is formed from:
A. Glycerol and three fatty acids
B. Glycerol and two fatty acids
C. Glycerol and one fatty acid
D. Three glycerols and one fatty acid
Correct Answer: A
Rationale: Triglycerides consist of one glycerol molecule and three fatty acids joined by ester bonds
formed via condensation. [100% CORRECT]
Q5: Protein Structure
The student is reviewing proteins. Which level of protein structure is determined by hydrogen bonds
between amino acids?
A. Primary
B. Secondary
C. Tertiary
D. Quaternary
Correct Answer: B
Rationale: Secondary structure (α-helix, β-pleated sheet) is maintained by hydrogen bonds between
the carboxyl group of one amino acid and the amino group of another. Primary is sequence, tertiary
is 3D folding, quaternary is multiple polypeptides. [100% CORRECT]
Q6: Enzyme Specificity
The student is reviewing enzymes. The induced-fit model explains:
A. Why enzymes are specific
B. Why enzymes lower activation energy
C. Why enzymes are affected by pH
D. Why enzymes are proteins
Correct Answer: A
Rationale: The induced-fit model states that the active site changes shape slightly to fit the
substrate, explaining specificity and how the enzyme-substrate complex forms. [100% CORRECT]
Q7: Enzyme Denaturation
, 3
The student is reviewing enzymes. Which condition causes denaturation?
A. Low temperature
B. Extreme pH
C. Optimum substrate concentration
D. Low enzyme concentration
Correct Answer: B
Rationale: Extreme pH disrupts ionic and hydrogen bonds, altering the tertiary structure and
denaturing the enzyme. Low temperature reduces activity but does not denature. [100% CORRECT]
Q8: Competitive Inhibition
The student is reviewing inhibition. A competitive inhibitor:
A. Binds to the active site
B. Binds to an allosteric site
C. Increases Vmax
D. Cannot be overcome by increasing substrate
Correct Answer: A
Rationale: Competitive inhibitors have a shape similar to the substrate and bind to the active site,
blocking substrate binding. Increasing substrate concentration can overcome it. Vmax remains
unchanged. [100% CORRECT]
Q9: DNA Structure
The student is reviewing nucleic acids. In DNA, the two strands are held together by:
A. Covalent bonds
B. Hydrogen bonds
C. Ionic bonds
D. Peptide bonds
Correct Answer: B
Rationale: Hydrogen bonds form between complementary base pairs (A-T, C-G) on opposite strands.
Covalent bonds form the sugar-phosphate backbone. [100% CORRECT]
Q10: ATP Structure
The student is reviewing ATP. ATP is a:
A. Nucleotide derivative
B. Protein
C. Carbohydrate
D. Lipid
Correct Answer: A
