Worked examplesThree real structure and function of biological macromolecules questions
From the practice pool, not the mock papers — each with the reasoning that produces the answer.
61% of them come with a figure. Reading the graph or diagram correctly is most of the work here before any content knowledge applies.
83% test a single AP skill: Concept Explanation. That makes this topic unusually predictable to prepare for.
Concept Explanation
A phospholipid contains an unsaturated fatty acid tail with a cis double bond. Which structural effect is most directly associated with that double bond?
- AThe double bond converts the phospholipid into a nucleic acid.
- BCis unsaturation introduces a kink that reduces tight tail packingcorrect
- CThe double bond creates peptide bonds between adjacent phospholipids.
- DThe double bond removes the phosphate-containing head group.
Why B is correct
A cis double bond in an unsaturated fatty acid creates a kink in the tail. Kinked tails pack less tightly than straight saturated tails, which can affect membrane fluidity.
The stem asks students to explain a specific mechanism, not just recall a unit term: "A phospholipid contains an unsaturated fatty acid tail with a cis double bond. Which structural effect is most...". The correct choice is supported by A cis double bond in an unsaturated fatty acid creates a kink in the tail. The tempting alternatives such as double bond converts the phospholipid into a nucleic acid or double bond creates peptide bonds between adjacent phospholipids fail because they do not produce the same outcome described in the stem.
Concept Explanation
Glycogen is a highly branched polysaccharide used for energy storage in animals. Which feature of branching is most directly useful for rapid glucose mobilization?
- ABranches make glycogen a nucleic acid with complementary bases.
- BBranches remove all covalent bonds from the polysaccharide.
- CMore branch ends provide more sites for enzyme actioncorrect
- DHigh specific heat is caused by water molecules releasing heat without changing molecular motion.
Why C is correct
Branching in glycogen creates many terminal ends. Enzymes can act at these ends, allowing glucose units to be added or removed efficiently during storage and mobilization.
The stem asks students to explain a specific mechanism, not just recall a unit term: "Glycogen is a highly branched polysaccharide used for energy storage in animals. Which feature of branching is...". The correct choice is supported by Branching in glycogen creates many terminal ends. The tempting alternatives such as Branches make glycogen a nucleic acid with complementary bases or Branches remove all covalent bonds from the polysaccharide fail because they do not produce the same outcome described in the stem.
Visual Representations · with figure
Which statement best matches the evidence shown in Figure 1?
- AMarker A: Kinases transfer phosphate groups from ATP to target proteins.
- BMarker B: Phosphatases can remove phosphate groups and reverse signaling changes.
- CMarker C: Covalent modification can change protein shape and activitycorrect
- DMarker D: Protein shape affects whether binding sites are accessible.
Why C is correct
Figure 1 must be used to determine which marker is supported by the visual model. Marker C: Phosphorylation can change protein conformation and alter activity. Phosphorylation can add negative charge and alter interactions among amino acid side chains. The model links phosphorylation to a conformational change that exposes the active site and increases substrate binding.
The evidence in the prompt matters before the topic label: "A protein model shows a regulatory site that can be phosphorylated. When a phosphate group is added, nearby...". The supported answer is "Adding a phosphate can change protein conformation and regulate activity" because The model links phosphorylation to a conformational change that exposes the active site and increases substrate binding. Distractors such as protein active site is always unaffected by changes away from the... or Phosphate groups remove all charges from amino acid side chains either ignore the stated pattern or name a related concept without matching the evidence.
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Last reviewed 2026-08-28. Topic and unit names follow the
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