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syno AQA Biology synoptic questions

Cross-topic AQA A-level Biology questions designed to make students connect ideas from different parts of the course. Free MCQs include clues and explanations.

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syno
Question bank
150 questions
Course stage
Year 13 / A-level only

Sample questions

QUESTION 1 · syno · LEVEL 3

A substitution mutation occurs in the gene coding for the enzyme amylase. How could this specifically affect the digestion of starch?

  • The mutation changes the primary structure, which alters the ionic and hydrogen bonds in the tertiary structure, changing the active site shape so starch can no longer bind and be hydrolysed.
  • The mutation changes the starch molecule directly, making it impossible for normal amylase to form an enzyme-substrate complex.
  • The mutation stops all transcription in the pancreas, completely preventing any digestive enzymes from being secreted.
  • The mutation alters the active site, causing the amylase to begin digesting proteins instead of carbohydrates.
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This question links Topic 4 (Mutations) with Topic 1 (Protein structure) and Topic 3 (Digestion).

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Answer: The mutation changes the primary structure, which alters the ionic and hydrogen bonds in the tertiary structure, changing the active site shape so starch can no longer bind and be hydrolysed.

Synoptic link: Mutations alter the DNA base sequence, changing the amino acid sequence (primary structure). This alters the folding of the tertiary structure, changing the enzyme's active site. Without a complementary active site, starch (the substrate) cannot be hydrolysed.

QUESTION 2 · syno · LEVEL 3

How do the transport mechanisms of the cell-surface membrane relate to the establishment of the resting potential in a neurone?

  • The sodium-potassium pump uses ATP for active transport against the gradient, while specific channel proteins allow the facilitated diffusion of potassium ions down their gradient.
  • Sodium and potassium ions both cross the phospholipid bilayer freely via simple diffusion to establish the electrical gradient.
  • The resting potential relies exclusively on the active transport of negatively charged proteins via exocytosis.
  • Co-transport proteins move sodium ions in simultaneously with glucose to maintain the $-70mV$ charge.
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This question links Topic 1 (Membrane transport) with Topic 6 (Nerve impulses).

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Answer: The sodium-potassium pump uses ATP for active transport against the gradient, while specific channel proteins allow the facilitated diffusion of potassium ions down their gradient.

Synoptic link: The resting potential (Topic 6) is a direct application of membrane transport (Topic 1). It requires the $Na^+/K^+$ pump (active transport requiring ATP) and open $K^+$ channels (facilitated diffusion).

QUESTION 3 · syno · LEVEL 4

During intense exercise, the Bohr effect occurs. How does anaerobic respiration in muscle tissue lead to this effect?

  • Anaerobic respiration produces lactate, which lowers blood pH; this acidic environment alters the tertiary structure of haemoglobin, reducing its affinity for oxygen and promoting unloading.
  • Anaerobic respiration uses up all the oxygen, leaving a vacuum that sucks oxygen out of the red blood cells.
  • Lactate directly competitively inhibits the oxygen-binding sites on the haem group.
  • Anaerobic respiration releases massive amounts of $CO_2$, which directly boils the haemoglobin protein.
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This question links Topic 5 (Respiration) with Topic 3 (Haemoglobin/Mass transport).

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Answer: Anaerobic respiration produces lactate, which lowers blood pH; this acidic environment alters the tertiary structure of haemoglobin, reducing its affinity for oxygen and promoting unloading.

Synoptic link: Anaerobic respiration produces lactic acid. A drop in pH alters the hydrogen/ionic bonds in haemoglobin's tertiary structure, lowering its affinity for oxygen (the Bohr effect), thereby delivering more $O_2$ to respiring tissues.

QUESTION 4 · syno · LEVEL 3

What is the relationship between the light-independent reaction of photosynthesis and the concept of Gross Primary Production (GPP)?

  • The Calvin cycle synthesises hexose sugars from $CO_2$; GPP is the total chemical energy stored in these newly synthesised organic biological molecules within a given area.
  • The light-independent reaction destroys biomass through photorespiration, which is subtracted from GPP to calculate NPP.
  • GPP measures the total amount of light energy absorbed by chlorophyll during the light-dependent reaction only.
  • The Calvin cycle relies entirely on GPP to provide the ATP necessary to reduce GP to TP.
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This question links Topic 5 (Photosynthesis) with Topic 5 (Ecosystems/Energy transfer).

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Answer: The Calvin cycle synthesises hexose sugars from $CO_2$; GPP is the total chemical energy stored in these newly synthesised organic biological molecules within a given area.

Synoptic link: The Calvin cycle (light-independent reaction) fixes carbon into organic molecules like glucose. GPP is the ecological measurement of this exact biochemical process—the total chemical energy store created by plants.

QUESTION 5 · syno · LEVEL 3

How do the physical properties of the phospholipid bilayer explain the specific cellular action of Antidiuretic Hormone (ADH) in the kidneys?

  • The hydrophobic core of the bilayer prevents water from easily crossing the collecting duct membrane; ADH triggers the insertion of aquaporin channel proteins to allow rapid facilitated diffusion (osmosis).
  • ADH acts as a non-polar lipid that physically dissolves the phospholipid bilayer, letting water leak into the blood.
  • The bilayer actively pumps water out; ADH is a competitive inhibitor of this water pump.
  • ADH binds to the hydrophilic phosphate heads, reversing their charge to repel water molecules.
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This question links Topic 1 (Cell membranes) with Topic 6 (Osmoregulation).

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Answer: The hydrophobic core of the bilayer prevents water from easily crossing the collecting duct membrane; ADH triggers the insertion of aquaporin channel proteins to allow rapid facilitated diffusion (osmosis).

Synoptic link: Because water is polar, it cannot cross the hydrophobic lipid bilayer efficiently. ADH (Topic 6) solves this problem by causing aquaporins (channel proteins, Topic 1) to fuse with the membrane, facilitating rapid osmosis.

QUESTION 6 · syno · LEVEL 2

A plant is infected by a virus. How does the structure of the virus prevent the plant from fighting it off with antibiotics?

  • Viruses are acellular and lack the metabolic pathways and cell wall structures (like peptidoglycan) that antibiotics are designed to disrupt.
  • Viruses possess a thick waxy cuticle that prevents the antibiotic from diffusing into their cytoplasm.
  • Plant viruses mutate their DNA so rapidly that antibiotics cannot bind to their ribosomes.
  • Plants do not possess a circulatory system, so the antibiotic cannot be transported to the virus.
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This question links Topic 2 (Cell structure/Viruses) with Topic 2/4 (Antibiotics/Immunity).

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Answer: Viruses are acellular and lack the metabolic pathways and cell wall structures (like peptidoglycan) that antibiotics are designed to disrupt.

Synoptic link: Viruses consist only of genetic material and a capsid. Antibiotics work by disrupting bacterial cell walls or prokaryotic ribosomes. Because viruses lack these structures and rely entirely on the host cell's machinery, antibiotics are ineffective against them.

QUESTION 7 · syno · LEVEL 2

Which biological molecules are synthesised using the nitrate ions ($NO_3^-$) absorbed by plant roots from the soil?

  • Amino acids (to make proteins), ATP, and nucleic acids (DNA and RNA).
  • Glucose, cellulose, and starch.
  • Triglycerides, phospholipids, and cholesterol.
  • Glycogen, chitin, and water.
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This question links Topic 5 (Nitrogen cycle) with Topic 1 (Biological molecules). Nitrogen is required for the amine group in amino acids and the nitrogenous base in nucleotides.

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Answer: Amino acids (to make proteins), ATP, and nucleic acids (DNA and RNA).

Synoptic link: The nitrogen cycle provides plants with nitrates. Nitrogen is an essential chemical element found in amino acids (proteins), ATP, and the nitrogenous bases of nucleotides (DNA/RNA). It is not found in standard carbohydrates or lipids.

QUESTION 8 · syno · LEVEL 3

How is the universal nature of the genetic code essential for the production of human insulin using genetically modified bacteria?

  • Because the code is universal, the specific DNA base triplets of the human insulin gene will be translated by the bacterial ribosomes into the exact same amino acid sequence.
  • It ensures that the bacterial restriction enzymes will only cut human DNA and not their own plasmids.
  • It means the bacterial cell wall is fully permeable to human mRNA.
  • It allows the bacteria to undergo mitosis exactly like a human eukaryotic cell.
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This question links Topic 4 (Genetic code) with Topic 8 (Recombinant DNA technology).

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Answer: Because the code is universal, the specific DNA base triplets of the human insulin gene will be translated by the bacterial ribosomes into the exact same amino acid sequence.

Synoptic link: 'Universal' means the same codons code for the same amino acids in almost all organisms. This is why a human gene inserted into a bacterium (in vivo cloning) correctly produces the human protein.

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