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AP® Biology · Unit 1 · Topic 1.5

Lipids: Topic Checklist (Biology 1.5)

Specific “I can…” statements for fatty acids, fats, phospholipids, steroids and cholesterol, each linked to the guide section and practice question that shows whether you can really do it.

Work through the list without notes. If you cannot do a statement, follow its link, then come back. Guide = study guide; Practice = practice questions.

Understanding

  • I can explain why most lipids are hydrophobic, using the polarity of C–H bonds, and say why lipids are not counted as polymers. (Guide: “What makes a molecule a lipid?”)
  • I can tell a saturated fatty acid from an unsaturated one, and explain what “more unsaturated” means. (Guide: Figure 1; Practice Q1)
  • I can describe how a fat is built from glycerol and three fatty acids, and say how many water molecules are released. (Guide: “Fats (triglycerides)”; Figure 2)
  • I can describe a phospholipid’s hydrophilic head and hydrophobic tails, and explain why phospholipids form a bilayer in water. (Guide: Figure 3; Practice Q2, Q5)
  • I can state the jobs of fats, steroid hormones, cholesterol and phospholipids, and recognise a steroid by its four fused rings. (Guide: “Structure decides function”)

Calculation and skills

  • I can calculate the mass of fat or carbohydrate needed to store a given amount of energy, with units on every line. (Guide: Worked example 1; Practice Q3, Q7)
  • I can describe a trend in a table or graph using quoted values, and estimate a value between two data points. (Guide: Worked example 2; Practice Q4)
  • I can calculate means from repeated trials and say whether the ranges overlap. (Practice Q6)

Reasoning

  • I can explain why more double bonds make a lipid more liquid at room temperature, using kinks and packing, not bond strength. (Guide: “Why kinks change whether a fat is solid or liquid”; Practice Q4)
  • I can predict how a change in the lipids a cell makes (more or fewer unsaturated tails, no cholesterol, no phospholipids) would affect its membranes, and justify the prediction. (Guide: Worked example 2; Practice Q5, Q6)
  • I can explain why fat is a better energy store than carbohydrate for an animal that must carry its store. (Guide: Worked example 1; Practice Q7)
  • I can identify the independent variable and the purpose of a control in an experiment on membrane lipids. (Practice Q6)

All ticked? Move on to Topic 1.6, Nucleic Acids, or return to the course roadmap.

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