Advanced Topic 997 of 1102 Biochemistry, Environment & Industry

Cholesterol

A steroid in membranes and a precursor to hormones.

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In-depth explanation of Cholesterol

Cholesterol is a rigid steroid with a four-ring skeleton, a short hydrocarbon side chain and a hydroxyl group. Within animal cell membranes it sits between phospholipids, buffering fluidity so that membranes stay stable across a range of temperatures. It is the precursor of steroid hormones such as cortisol and oestrogen, of bile acids that emulsify dietary fat, and of vitamin D synthesised in skin under UV light. Cholesterol is carried in blood by lipoproteins, with LDL delivering it to tissues and HDL removing the excess. Excess LDL cholesterol can deposit as plaque in artery walls.

Going deeper: Cholesterol

Key ideas: A steroid with four fused rings, one hydroxyl group and a branched hydrocarbon tail, C27H46O. Embedded in animal membranes it reduces fluidity at high temperature and prevents packing at low temperature. It is the precursor of bile acids, vitamin D and steroid hormones. Carried in blood by LDL (to tissues) and HDL (back to liver).

Common mistakes and connections: Students call LDL bad cholesterol as if it were a different molecule; the molecule is identical, only the carrier lipoprotein differs. Plants have no cholesterol, they make sterols such as sitosterol. Dietary cholesterol affects blood levels less than saturated fat. Links to hormones and phospholipids.

Visualization of Cholesterol

Total blood cholesterol categories. Excess LDL cholesterol is the part that can deposit as plaque in artery walls. The interactive lesson shows this as a live animation or chart.

Worked example and use case

Statin drugs lower blood cholesterol by inhibiting the enzyme HMG-CoA reductase.

Frequently asked questions about Cholesterol

What is Cholesterol?

A steroid in membranes and a precursor to hormones.

Is Cholesterol a beginner, intermediate or advanced topic?

Cholesterol is a advanced topic in Biochemistry, Environment & Industry. It builds on beginner and intermediate topics, so review those first if needed.

What should I learn before Cholesterol?

Study these earlier topics in Biochemistry, Environment & Industry first: Saturated and Unsaturated Fatty Acids, Trans Fats, Phospholipids.

What comes after Cholesterol?

The next topics in Biochemistry, Environment & Industry are DNA Structure and RNA Types.

Can I practise Cholesterol with quizzes?

Yes. The interactive lesson includes a self-check question on Cholesterol, and the Biochemistry, Environment & Industry quiz draws on every topic in this area.

Where Cholesterol fits in Biochemistry, Environment & Industry

Cholesterol is topic 22 of 127 in Biochemistry, Environment & Industry.