⚡ Show all reasoning — the AI marks against the AQA mark scheme. Partial credit for correct biology even if wording differs.
1 markEnzyme definitionAQA 8461 style
Which of the following best describes an enzyme?
A A substrate that speeds up chemical reactions
B A biological catalyst made of protein that speeds up reactions without being used up
C A molecule that is permanently changed by chemical reactions
D A protein that slows down harmful chemical reactions
3 marksDenaturation explanationAQA 8461 P1 style
Explain what happens to an enzyme when the temperature rises significantly above its optimum temperature. (3 marks)
Hint: Sequence: bonds broken → active site shape changes → substrate cannot bind → enzyme denatured (permanent).
+30 XP
1 markpH and enzymeAQA 8461 style
Why does pepsin (stomach enzyme) work best at pH 2 but not at pH 7?
A At pH 7, pepsin dissolves and cannot function
B At pH 7, the ionic bonds in pepsin's active site are changed, altering its shape so substrate cannot bind
C At pH 7, the substrate molecule changes shape and no longer fits the active site
D At pH 7, pepsin becomes too active and breaks down
4 marksDigestion enzymesAQA 8461 style
A student eats a cheese sandwich. Name the enzymes involved in digesting the carbohydrates, proteins and lipids in the sandwich, and state the products of each reaction. (4 marks)
Hint: Three food components (starch, protein, fat) → three enzymes → three sets of products. Add bile as a bonus point.
+40 XP
1 markLock and keyAQA 8461 style
Why can amylase digest starch but not proteins?
A Amylase is too small to bind to proteins
B Proteins are found in different parts of the body from amylase
C The active site of amylase is complementary in shape only to starch molecules, not protein molecules
D Proteins denature amylase before it can act on them