AQA AS LEVEL BIOLOGY ACTUAL FINAL PRACTICE
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QUESTIONS AND 100% CORRECT VERIFIED
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COMPLETE SOLUTIONS) 2026-2027 Q&A UPDATED
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Paper 1 and Paper 2 Combined Practice
Section 3.1: Biological Molecules
1. Which bond is formed when two amino acids join together in a condensation
reaction?
A) Glycosidic bond
B) Peptide bond
C) Ester bond
D) Phosphodiester bond
Rationale: A peptide bond forms between the amine group of one amino acid and
the carboxyl group of another, releasing water. Glycosidic bonds join sugars,
ester bonds join glycerol to fatty acids, and phosphodiester bonds join
nucleotides.
,2. Which of the following is a correct description of the quaternary structure of a
protein?
A) The sequence of amino acids in a polypeptide chain
B) The folding of a polypeptide chain into an alpha helix or beta pleated sheet
C) The overall three-dimensional shape of a single polypeptide chain
D) The arrangement of multiple polypeptide chains and prosthetic groups
Rationale: Quaternary structure refers to the association of two or more
polypeptide chains, and may include prosthetic groups. Primary is the amino
acid sequence, secondary is alpha helix or beta pleated sheet, tertiary is the 3D
shape of one chain.
3. A molecule of DNA contains 28% adenine. What percentage of the DNA is
cytosine?
A) 28%
B) 44%
C) 22%
D) 14%
Rationale: By complementary base pairing, adenine pairs with thymine, so
thymine is also 28%. This accounts for 56%. The remaining 44% is shared
equally between cytosine and guanine, so cytosine = 22%.
4. Which property of water makes it an effective coolant in living organisms?
A) It is a polar molecule
B) It is a metabolite in many reactions
C) It has a high specific heat capacity
D) It acts as a solvent
Rationale: High specific heat capacity means water absorbs a lot of heat energy
for little temperature change, making it an effective coolant. Polarity and solvent
action relate to transport, not cooling.
,5. The enzyme amylase catalyses the hydrolysis of starch into maltose. Which of the
following describes the mechanism of enzyme action?
A) Lock and key only
B) Induced fit only
C) Both lock and key and induced fit
D) Neither lock and key nor induced fit
Rationale: The induced fit model is the currently accepted mechanism, but the
lock and key model is a simplified earlier model. Exam questions may credit both
depending on context. The induced fit model explains how the active site moulds
around the substrate.
6. Which of the following is a reducing sugar?
A) Sucrose
B) Maltose
C) Starch
D) Cellulose
Rationale: Maltose is a disaccharide of glucose and is a reducing sugar. Sucrose
is non-reducing, and starch and cellulose are polysaccharides.
7. In a test for lipids, which reagent is used and what is a positive result?
A) Ethanol, then water — milky white emulsion
B) Benedict's solution — brick red precipitate
C) Iodine solution — blue-black colour
D) Biuret reagent — purple colour
Rationale: The emulsion test uses ethanol to dissolve lipids, then water to
precipitate them as a milky-white emulsion. Benedict's tests reducing sugars,
iodine tests starch, and Biuret tests protein.
, 8. Which of the following is NOT a function of the enzyme DNA helicase?
A) Breaking hydrogen bonds between complementary bases
B) Unwinding the DNA double helix
C) Joining adjacent nucleotides together
D) Separating the two DNA strands
Rationale: DNA helicase unwinds and separates strands by breaking hydrogen
bonds. Joining nucleotides is the role of DNA polymerase.
9. Which statement about ATP is correct?
A) ATP is a nucleotide derivative that releases energy when hydrolysed to ADP
and Pi
B) ATP contains three phosphate groups and two sugar molecules
C) ATP is a long-term energy store in cells
D) ATP is formed by the hydrolysis of ADP
Rationale: ATP is a phosphorylated nucleotide. Hydrolysis of the terminal
phosphate bond releases energy. ATP is not a long-term store; it is an immediate
energy source.
10. Which of the following correctly describes the structure of a triglyceride?
A) Glycerol and two fatty acids
B) Glycerol and three fatty acids
C) Three glycerol molecules and one fatty acid
D) Glycerol and one fatty acid
Rationale: A triglyceride is formed from one glycerol molecule and three fatty
acid molecules joined by ester bonds via condensation reactions.
11. Which level of protein structure is determined by the sequence of amino acids?
A) Primary
B) Secondary
EXAM PREP WITH ALL POSSIBLE COMPLETE
DETAILED AND MOST TESTED PRACTICE
QUESTIONS AND 100% CORRECT VERIFIED
ANSWERS FULLY SOLVED WITH CERTIFIED
RATIONALES PLUS RELIABLE ANSWER KEY (100%
COMPLETE SOLUTIONS) 2026-2027 Q&A UPDATED
VERSION 100% GUARANTEED PASS INSTANT
DOWNLOAD PDF
Paper 1 and Paper 2 Combined Practice
Section 3.1: Biological Molecules
1. Which bond is formed when two amino acids join together in a condensation
reaction?
A) Glycosidic bond
B) Peptide bond
C) Ester bond
D) Phosphodiester bond
Rationale: A peptide bond forms between the amine group of one amino acid and
the carboxyl group of another, releasing water. Glycosidic bonds join sugars,
ester bonds join glycerol to fatty acids, and phosphodiester bonds join
nucleotides.
,2. Which of the following is a correct description of the quaternary structure of a
protein?
A) The sequence of amino acids in a polypeptide chain
B) The folding of a polypeptide chain into an alpha helix or beta pleated sheet
C) The overall three-dimensional shape of a single polypeptide chain
D) The arrangement of multiple polypeptide chains and prosthetic groups
Rationale: Quaternary structure refers to the association of two or more
polypeptide chains, and may include prosthetic groups. Primary is the amino
acid sequence, secondary is alpha helix or beta pleated sheet, tertiary is the 3D
shape of one chain.
3. A molecule of DNA contains 28% adenine. What percentage of the DNA is
cytosine?
A) 28%
B) 44%
C) 22%
D) 14%
Rationale: By complementary base pairing, adenine pairs with thymine, so
thymine is also 28%. This accounts for 56%. The remaining 44% is shared
equally between cytosine and guanine, so cytosine = 22%.
4. Which property of water makes it an effective coolant in living organisms?
A) It is a polar molecule
B) It is a metabolite in many reactions
C) It has a high specific heat capacity
D) It acts as a solvent
Rationale: High specific heat capacity means water absorbs a lot of heat energy
for little temperature change, making it an effective coolant. Polarity and solvent
action relate to transport, not cooling.
,5. The enzyme amylase catalyses the hydrolysis of starch into maltose. Which of the
following describes the mechanism of enzyme action?
A) Lock and key only
B) Induced fit only
C) Both lock and key and induced fit
D) Neither lock and key nor induced fit
Rationale: The induced fit model is the currently accepted mechanism, but the
lock and key model is a simplified earlier model. Exam questions may credit both
depending on context. The induced fit model explains how the active site moulds
around the substrate.
6. Which of the following is a reducing sugar?
A) Sucrose
B) Maltose
C) Starch
D) Cellulose
Rationale: Maltose is a disaccharide of glucose and is a reducing sugar. Sucrose
is non-reducing, and starch and cellulose are polysaccharides.
7. In a test for lipids, which reagent is used and what is a positive result?
A) Ethanol, then water — milky white emulsion
B) Benedict's solution — brick red precipitate
C) Iodine solution — blue-black colour
D) Biuret reagent — purple colour
Rationale: The emulsion test uses ethanol to dissolve lipids, then water to
precipitate them as a milky-white emulsion. Benedict's tests reducing sugars,
iodine tests starch, and Biuret tests protein.
, 8. Which of the following is NOT a function of the enzyme DNA helicase?
A) Breaking hydrogen bonds between complementary bases
B) Unwinding the DNA double helix
C) Joining adjacent nucleotides together
D) Separating the two DNA strands
Rationale: DNA helicase unwinds and separates strands by breaking hydrogen
bonds. Joining nucleotides is the role of DNA polymerase.
9. Which statement about ATP is correct?
A) ATP is a nucleotide derivative that releases energy when hydrolysed to ADP
and Pi
B) ATP contains three phosphate groups and two sugar molecules
C) ATP is a long-term energy store in cells
D) ATP is formed by the hydrolysis of ADP
Rationale: ATP is a phosphorylated nucleotide. Hydrolysis of the terminal
phosphate bond releases energy. ATP is not a long-term store; it is an immediate
energy source.
10. Which of the following correctly describes the structure of a triglyceride?
A) Glycerol and two fatty acids
B) Glycerol and three fatty acids
C) Three glycerol molecules and one fatty acid
D) Glycerol and one fatty acid
Rationale: A triglyceride is formed from one glycerol molecule and three fatty
acid molecules joined by ester bonds via condensation reactions.
11. Which level of protein structure is determined by the sequence of amino acids?
A) Primary
B) Secondary
