AQA A-Level Biology Ultimate QUESTION Bank |
300+ Practice QUESTIONs, Model Answers & Mark
Scheme
QUESTION 1
A student is studying the structure of carbohydrates. Which of the
following best describes the formation of a glycosidic bond between
two alpha-glucose molecules?
• A. Condensation reaction involving carbons 1 and 4, releasing a
molecule of water.
• B. Hydrolysis reaction involving carbons 1 and 6, requiring a
molecule of water.
• C. Condensation reaction involving carbons 1 and 6, releasing
carbon dioxide.
• D. Esterification reaction between a glycerol molecule and fatty
acids.
Correct Answer: A. Condensation reaction involving carbons 1 and 4,
releasing a molecule of water.
Detailed Rationale: A glycosidic bond is formed by a condensation
reaction between the hydroxyl groups on carbon 1 and carbon 4 of
adjacent alpha-glucose molecules, releasing a molecule of water as a
byproduct.
QUESTION 2
,An electron microscope is used to study cellular ultrastructure. Which
of the following is a key advantage of a transmission electron
microscope (TEM) compared to a scanning electron microscope (SEM)?
• A. TEM provides a three-dimensional image of the surface of the
specimen.
• B. TEM allows for a much higher maximum resolution to view
internal cellular details.
• C. TEM can be used to observe living, unstained cells in real-time.
• D. TEM requires much simpler and faster sample preparation
techniques.
Correct Answer: B. TEM allows for a much higher maximum resolution
to view internal cellular details.
Detailed Rationale: A transmission electron microscope (TEM) focuses a
beam of electrons through a thin specimen, allowing internal
ultrastructural details (like chloroplast membranes and cristae) to be
seen with a very high resolution. SEM provides three-dimensional
surface images with lower resolution.
QUESTION 3
Which feature of the human gas exchange system maximises the rate of
diffusion of oxygen into the blood?
• A. Thick alveolar walls composed of multiple layers of ciliated
epithelial cells.
• B. A small surface area to volume ratio provided by spherical
alveoli.
, • C. A large network of capillaries maintaining a steep concentration
gradient.
• D. Slow blood flow through pulmonary capillaries to prevent gas
exchange.
Correct Answer: C. A large network of capillaries maintaining a steep
concentration gradient.
Detailed Rationale: A large network of capillaries surrounds the alveoli,
continuously circulating deoxygenated blood and removing oxygenated
blood, which maintains a steep concentration gradient for rapid gas
diffusion.
QUESTION 4
During transcription in a eukaryotic cell, which enzyme is primarily
responsible for synthesising pre-mRNA from a DNA template strand?
• A. DNA polymerase
• B. DNA ligase
• C. RNA polymerase
• D. Reverse transcriptase
Correct Answer: C. RNA polymerase
Detailed Rationale: RNA polymerase binds to the promoter region of a
gene and catalyses the formation of phosphodiester bonds between
free RNA nucleotides, using the DNA template strand to build pre-
mRNA.
QUESTION 5
, Where specifically do the light-dependent reactions of photosynthesis
take place within a chloroplast?
• A. Stroma
• B. Thylakoid membranes
• C. Outer chloroplast membrane
• D. Cytoplasm of the plant cell
Correct Answer: B. Thylakoid membranes
Detailed Rationale: The light-dependent reactions take place across the
thylakoid membranes, which contain photosystems, photosynthetic
pigments, and ATP synthase required for photophosphorylation.
QUESTION 6
What causes the depolarisation phase of an action potential along a
myelinated neurone axon?
• A. Influx of sodium ions through voltage-gated sodium channels.
• B. Efflux of potassium ions through voltage-gated potassium
channels.
• C. Active transport of sodium ions out of the axon by the sodium-
potassium pump.
• D. Movement of calcium ions into the presynaptic knob.
Correct Answer: A. Influx of sodium ions through voltage-gated sodium
channels.
Detailed Rationale: When a threshold is reached, voltage-gated sodium
channels open, causing a rapid influx of sodium ions (𝑁𝑎+ ) down their
300+ Practice QUESTIONs, Model Answers & Mark
Scheme
QUESTION 1
A student is studying the structure of carbohydrates. Which of the
following best describes the formation of a glycosidic bond between
two alpha-glucose molecules?
• A. Condensation reaction involving carbons 1 and 4, releasing a
molecule of water.
• B. Hydrolysis reaction involving carbons 1 and 6, requiring a
molecule of water.
• C. Condensation reaction involving carbons 1 and 6, releasing
carbon dioxide.
• D. Esterification reaction between a glycerol molecule and fatty
acids.
Correct Answer: A. Condensation reaction involving carbons 1 and 4,
releasing a molecule of water.
Detailed Rationale: A glycosidic bond is formed by a condensation
reaction between the hydroxyl groups on carbon 1 and carbon 4 of
adjacent alpha-glucose molecules, releasing a molecule of water as a
byproduct.
QUESTION 2
,An electron microscope is used to study cellular ultrastructure. Which
of the following is a key advantage of a transmission electron
microscope (TEM) compared to a scanning electron microscope (SEM)?
• A. TEM provides a three-dimensional image of the surface of the
specimen.
• B. TEM allows for a much higher maximum resolution to view
internal cellular details.
• C. TEM can be used to observe living, unstained cells in real-time.
• D. TEM requires much simpler and faster sample preparation
techniques.
Correct Answer: B. TEM allows for a much higher maximum resolution
to view internal cellular details.
Detailed Rationale: A transmission electron microscope (TEM) focuses a
beam of electrons through a thin specimen, allowing internal
ultrastructural details (like chloroplast membranes and cristae) to be
seen with a very high resolution. SEM provides three-dimensional
surface images with lower resolution.
QUESTION 3
Which feature of the human gas exchange system maximises the rate of
diffusion of oxygen into the blood?
• A. Thick alveolar walls composed of multiple layers of ciliated
epithelial cells.
• B. A small surface area to volume ratio provided by spherical
alveoli.
, • C. A large network of capillaries maintaining a steep concentration
gradient.
• D. Slow blood flow through pulmonary capillaries to prevent gas
exchange.
Correct Answer: C. A large network of capillaries maintaining a steep
concentration gradient.
Detailed Rationale: A large network of capillaries surrounds the alveoli,
continuously circulating deoxygenated blood and removing oxygenated
blood, which maintains a steep concentration gradient for rapid gas
diffusion.
QUESTION 4
During transcription in a eukaryotic cell, which enzyme is primarily
responsible for synthesising pre-mRNA from a DNA template strand?
• A. DNA polymerase
• B. DNA ligase
• C. RNA polymerase
• D. Reverse transcriptase
Correct Answer: C. RNA polymerase
Detailed Rationale: RNA polymerase binds to the promoter region of a
gene and catalyses the formation of phosphodiester bonds between
free RNA nucleotides, using the DNA template strand to build pre-
mRNA.
QUESTION 5
, Where specifically do the light-dependent reactions of photosynthesis
take place within a chloroplast?
• A. Stroma
• B. Thylakoid membranes
• C. Outer chloroplast membrane
• D. Cytoplasm of the plant cell
Correct Answer: B. Thylakoid membranes
Detailed Rationale: The light-dependent reactions take place across the
thylakoid membranes, which contain photosystems, photosynthetic
pigments, and ATP synthase required for photophosphorylation.
QUESTION 6
What causes the depolarisation phase of an action potential along a
myelinated neurone axon?
• A. Influx of sodium ions through voltage-gated sodium channels.
• B. Efflux of potassium ions through voltage-gated potassium
channels.
• C. Active transport of sodium ions out of the axon by the sodium-
potassium pump.
• D. Movement of calcium ions into the presynaptic knob.
Correct Answer: A. Influx of sodium ions through voltage-gated sodium
channels.
Detailed Rationale: When a threshold is reached, voltage-gated sodium
channels open, causing a rapid influx of sodium ions (𝑁𝑎+ ) down their
