Metabolism

How the body turns food into energy, building blocks and signals.

1. Energy and ATP

   How cells couple reactions to ATP, pass electrons to NAD+, FAD and NADP+, make ATP from a proton gradient and use energy organ by organ.

2. Glucose

   How glucose is absorbed and enters cells, and how glycolysis, pyruvate dehydrogenase, the citric acid cycle and oxidative phosphorylation make ATP from it.

3. Fed and fasting

   How insulin and glucagon switch the body between storing and releasing fuel, from glycogen to gluconeogenesis, ketone bodies and the course of a fast.

4. Fats

   How the body digests fat, carries it in lipoproteins, burns and makes fatty acids, and why linoleic and α-linolenic acid must come from food.

5. Cholesterol

   How human cells make, sense, take up and remove cholesterol, from the mevalonate pathway to the LDL receptor, PCSK9 and bile acids.

6. Amino acids and nitrogen

   How dietary protein is digested and absorbed, how amino groups pass through transamination and the urea cycle, and what phenylketonuria shows.

7. Folate, B12 and one-carbon metabolism

   How folate and vitamin B12 transfer single carbon atoms to DNA bases and methionine, and why lack of either causes megaloblastic anaemia.

8. How the body processes medicines

   First-pass metabolism, the cytochrome P450 enzymes, conjugation, drug transporters, induction and inhibition, and the inherited differences behind them.

9. From genes to proteins

   How DNA encodes proteins, how genes are transcribed, spliced and translated, and how variants in PAH, HBB, LDLR, ALDH2 and LCT change traits.

10. The cell and its compartments

    How membranes, pumps and organelles divide the chemistry of a human cell, and how insulin at the cell surface changes which genes are transcribed.

11. Vitamins as cofactors

    How B vitamins and vitamins C and K serve human enzymes as cofactors, which diseases their lack causes, and what supplement trials in adults found.

12. Hormones and signalling

    How insulin, glucagon, adrenaline, cortisol, thyroid hormones, leptin, ghrelin and GLP-1 act on receptors and second messengers, and how feedback limits them.