Core concept
Energy and ATP
Cells capture energy from food as ATP and spend it on pumping, moving and building.
Every cell runs on ATP. Cells break down food molecules and capture part of the released energy by making ATP; they spend ATP to pump ions against their gradients, to contract, and to build large molecules. Most ATP is made in mitochondria, which need a steady supply of oxygen.
That is why tissues with a high, unstoppable demand are the most fragile when blood flow fails. Heart muscle beats every second of your life and relies almost entirely on oxygen, so a blocked coronary artery injures it within minutes. When you meet any active process, ask where its ATP comes from and what happens when the supply stops.
Where it shows up
Chemistry and physics for physiology
Cells
Muscle tissue
- The sliding filament model and cross-bridge cycle
- Muscle energy and fatigue
- Muscle fiber types and exercise
The endocrine system
- The pancreas and blood glucose
Metabolism and nutrition
- Nutrients, vitamins and minerals
- Carbohydrate metabolism in detail
- Lipid and protein metabolism
- Fed and fasting states
- Energy balance and body temperature