Page 1 of 70
AQA A LEVEL BIOLOGY JUNE 2026 PAPER 1 |
QUESTION PAPER + MARK SCHEME
(VERIFIED) | LATEST UPDATE 2026/2027 |
PRACTICE QUESTIONS AND ANSWERS |
EXAM REVIEW.
TABLE OF CONTENTS
1. Biological Molecules
2. Cells and Cell Structure
3. Exchange and Transport
4. Genetic Information, Variation, and Relationships
5. Practical Skills and Mathematical Techniques
6. Exam Technique and Mark Scheme Application
, Page 2 of 70
Question 1: Which bond is formed when two amino acids are joined together in a
condensation reaction?
A) Glycosidic bond
B) Ester bond
C) Peptide bond
D) Phosphodiester bond
Correct Answer: C) Peptide bond
A peptide bond forms between the carboxyl group of one amino acid and the amino group of
another, with the elimination of water in a condensation reaction. Glycosidic bonds join
monosaccharides, ester bonds form between glycerol and fatty acids, and phosphodiester
bonds link nucleotides in nucleic acids.
Question 2: A student investigated the effect of pH on the activity of amylase. The results
showed an optimum pH of 7.0. Which statement best explains why activity decreased at pH
5.0?
A) The enzyme was denatured, changing the shape of the active site
B) The substrate was broken down before the enzyme could bind
C) The enzyme molecules collided less frequently with substrate molecules
D) The pH change increased the activation energy of the reaction
Correct Answer: A) The enzyme was denatured, changing the shape of the active site
Extreme pH changes disrupt the ionic and hydrogen bonds maintaining the tertiary structure
of the enzyme. This alters the shape of the active site so it is no longer complementary to the
substrate. Collision frequency affects rate but does not explain a decrease from the optimum
to pH 5. Denaturation is a permanent change in tertiary structure.
Question 3: In a DNA molecule, the proportion of adenine is 22%. What is the proportion of
guanine?
A) 22%
B) 28%
C) 44%
D) 56%
Correct Answer: B) 28%
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By Chargaff's rules, A = T and G = C. If A = 22%, then T = 22%. The remaining 56% is
shared equally between G and C, so G = 28%. This calculation requires understanding
complementary base pairing.
Question 4: Which of the following describes the structure of glycogen?
A) A polymer of β-glucose with 1,4 and 1,6 glycosidic bonds
B) A polymer of α-glucose with 1,4 and 1,6 glycosidic bonds
C) A polymer of α-glucose with only 1,4 glycosidic bonds
D) A polymer of β-glucose with only 1,4 glycosidic bonds
Correct Answer: B) A polymer of α-glucose with 1,4 and 1,6 glycosidic bonds
Glycogen is a highly branched polymer of α-glucose. The main chains are linked by 1,4
glycosidic bonds, and branch points are formed by 1,6 glycosidic bonds. Cellulose is a
polymer of β-glucose with 1,4 bonds only. Starch (amylopectin) is also α-glucose with 1,4 and
1,6 bonds but is less branched than glycogen.
Question 5: A triglyceride molecule is formed from:
A) One glycerol and three fatty acids
B) One glycerol and two fatty acids
C) Three glycerol molecules and one fatty acid
D) Two glycerol molecules and three fatty acids
Correct Answer: A) One glycerol and three fatty acids
A triglyceride consists of one glycerol molecule ester-bonded to three fatty acid molecules.
Each ester bond is formed by a condensation reaction between the hydroxyl group of glycerol
and the carboxyl group of a fatty acid, releasing three water molecules.
Question 6: Which test is used to detect the presence of a reducing sugar?
A) Biuret test
B) Benedict's test
C) Emulsion test
D) Iodine test
Correct Answer: B) Benedict's test
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Benedict's test detects reducing sugars. A positive result is a colour change from blue to
green, yellow, orange, or brick-red precipitate, depending on the concentration of reducing
sugar. Biuret tests for protein, the emulsion test for lipids, and iodine for starch.
Question 7: The primary structure of a protein refers to:
A) The sequence of amino acids joined by peptide bonds
B) The coiling of the polypeptide chain into an α-helix
C) The folding of the polypeptide into a 3D shape
D) The association of multiple polypeptide chains
Correct Answer: A) The sequence of amino acids joined by peptide bonds
The primary structure is the specific order of amino acids in the polypeptide chain,
determined by the gene. Secondary structure refers to local folding (α-helix or β-pleated
sheet). Tertiary structure is the overall 3D shape, and quaternary structure involves multiple
polypeptide chains.
Question 8: A solution containing starch and amylase was incubated at 37°C. Every 2
minutes, a sample was tested with iodine solution. After 10 minutes, the iodine test was
negative. What does this indicate?
A) All the starch had been hydrolysed to maltose
B) The amylase had been denatured
C) The starch had been converted to glucose
D) The reaction had not yet started
Correct Answer: A) All the starch had been hydrolysed to maltose
A negative iodine test means no starch is present. Amylase hydrolyses starch to maltose. The
absence of starch indicates complete hydrolysis. Amylase would not be denatured at 37°C
(optimum). Starch is not directly converted to glucose by amylase. The reaction would have
started immediately.
Question 9: Which of the following is a correct statement about the induced fit model of
enzyme action?
A) The active site is perfectly complementary to the substrate before binding
B) The active site changes shape slightly as the substrate binds
AQA A LEVEL BIOLOGY JUNE 2026 PAPER 1 |
QUESTION PAPER + MARK SCHEME
(VERIFIED) | LATEST UPDATE 2026/2027 |
PRACTICE QUESTIONS AND ANSWERS |
EXAM REVIEW.
TABLE OF CONTENTS
1. Biological Molecules
2. Cells and Cell Structure
3. Exchange and Transport
4. Genetic Information, Variation, and Relationships
5. Practical Skills and Mathematical Techniques
6. Exam Technique and Mark Scheme Application
, Page 2 of 70
Question 1: Which bond is formed when two amino acids are joined together in a
condensation reaction?
A) Glycosidic bond
B) Ester bond
C) Peptide bond
D) Phosphodiester bond
Correct Answer: C) Peptide bond
A peptide bond forms between the carboxyl group of one amino acid and the amino group of
another, with the elimination of water in a condensation reaction. Glycosidic bonds join
monosaccharides, ester bonds form between glycerol and fatty acids, and phosphodiester
bonds link nucleotides in nucleic acids.
Question 2: A student investigated the effect of pH on the activity of amylase. The results
showed an optimum pH of 7.0. Which statement best explains why activity decreased at pH
5.0?
A) The enzyme was denatured, changing the shape of the active site
B) The substrate was broken down before the enzyme could bind
C) The enzyme molecules collided less frequently with substrate molecules
D) The pH change increased the activation energy of the reaction
Correct Answer: A) The enzyme was denatured, changing the shape of the active site
Extreme pH changes disrupt the ionic and hydrogen bonds maintaining the tertiary structure
of the enzyme. This alters the shape of the active site so it is no longer complementary to the
substrate. Collision frequency affects rate but does not explain a decrease from the optimum
to pH 5. Denaturation is a permanent change in tertiary structure.
Question 3: In a DNA molecule, the proportion of adenine is 22%. What is the proportion of
guanine?
A) 22%
B) 28%
C) 44%
D) 56%
Correct Answer: B) 28%
, Page 3 of 70
By Chargaff's rules, A = T and G = C. If A = 22%, then T = 22%. The remaining 56% is
shared equally between G and C, so G = 28%. This calculation requires understanding
complementary base pairing.
Question 4: Which of the following describes the structure of glycogen?
A) A polymer of β-glucose with 1,4 and 1,6 glycosidic bonds
B) A polymer of α-glucose with 1,4 and 1,6 glycosidic bonds
C) A polymer of α-glucose with only 1,4 glycosidic bonds
D) A polymer of β-glucose with only 1,4 glycosidic bonds
Correct Answer: B) A polymer of α-glucose with 1,4 and 1,6 glycosidic bonds
Glycogen is a highly branched polymer of α-glucose. The main chains are linked by 1,4
glycosidic bonds, and branch points are formed by 1,6 glycosidic bonds. Cellulose is a
polymer of β-glucose with 1,4 bonds only. Starch (amylopectin) is also α-glucose with 1,4 and
1,6 bonds but is less branched than glycogen.
Question 5: A triglyceride molecule is formed from:
A) One glycerol and three fatty acids
B) One glycerol and two fatty acids
C) Three glycerol molecules and one fatty acid
D) Two glycerol molecules and three fatty acids
Correct Answer: A) One glycerol and three fatty acids
A triglyceride consists of one glycerol molecule ester-bonded to three fatty acid molecules.
Each ester bond is formed by a condensation reaction between the hydroxyl group of glycerol
and the carboxyl group of a fatty acid, releasing three water molecules.
Question 6: Which test is used to detect the presence of a reducing sugar?
A) Biuret test
B) Benedict's test
C) Emulsion test
D) Iodine test
Correct Answer: B) Benedict's test
, Page 4 of 70
Benedict's test detects reducing sugars. A positive result is a colour change from blue to
green, yellow, orange, or brick-red precipitate, depending on the concentration of reducing
sugar. Biuret tests for protein, the emulsion test for lipids, and iodine for starch.
Question 7: The primary structure of a protein refers to:
A) The sequence of amino acids joined by peptide bonds
B) The coiling of the polypeptide chain into an α-helix
C) The folding of the polypeptide into a 3D shape
D) The association of multiple polypeptide chains
Correct Answer: A) The sequence of amino acids joined by peptide bonds
The primary structure is the specific order of amino acids in the polypeptide chain,
determined by the gene. Secondary structure refers to local folding (α-helix or β-pleated
sheet). Tertiary structure is the overall 3D shape, and quaternary structure involves multiple
polypeptide chains.
Question 8: A solution containing starch and amylase was incubated at 37°C. Every 2
minutes, a sample was tested with iodine solution. After 10 minutes, the iodine test was
negative. What does this indicate?
A) All the starch had been hydrolysed to maltose
B) The amylase had been denatured
C) The starch had been converted to glucose
D) The reaction had not yet started
Correct Answer: A) All the starch had been hydrolysed to maltose
A negative iodine test means no starch is present. Amylase hydrolyses starch to maltose. The
absence of starch indicates complete hydrolysis. Amylase would not be denatured at 37°C
(optimum). Starch is not directly converted to glucose by amylase. The reaction would have
started immediately.
Question 9: Which of the following is a correct statement about the induced fit model of
enzyme action?
A) The active site is perfectly complementary to the substrate before binding
B) The active site changes shape slightly as the substrate binds
