Metabolic pathways are the series of chemical reactions that occur inside cells to convert nutrients into energy and useful molecules. They are essential for maintaining life, growth, and repair.
Here’s a overview of the major metabolic pathways in cells:
1. Glycolysis
- Where it happens: In the cytoplasm.
- What it does: Breaks down one molecule of glucose into two molecules of pyruvate.
- Energy yield: Produces a small amount of ATP and NADH.
- Type: Anaerobic (does not need oxygen).
2. Krebs Cycle (Citric Acid Cycle or TCA Cycle)
- Where it happens: In the mitochondrial matrix.
- What it does: Converts acetyl-CoA (from glucose, fats, or proteins) into carbon dioxide while producing NADH, FADH₂, and a little ATP.
- Type: Aerobic (requires oxygen indirectly).
3. Electron Transport Chain (ETC) and Oxidative Phosphorylation
- Where it happens: In the inner mitochondrial membrane.
- What it does: Uses NADH and FADH₂ from earlier steps to power ATP production.
- Energy yield: Produces the most ATP in the cell (about 34 per glucose).
- Type: Aerobic.
4. Beta-Oxidation of Fatty Acids
- Where it happens: In the mitochondria.
- What it does: Breaks down fatty acids into acetyl-CoA, which then enters the Krebs cycle to produce energy.
- Importance: Main energy source during fasting or long exercise.
5. Gluconeogenesis
- Where it happens: Mainly in the liver.
- What it does: Forms glucose from non-carbohydrate sources like amino acids, glycerol, and lactic acid.
- Importance: Keeps blood sugar levels stable during fasting.
6. Glycogenesis and Glycogenolysis
- Glycogenesis: Formation of glycogen (glucose storage form) in the liver and muscles.
- Glycogenolysis: Breakdown of glycogen back into glucose when the body needs energy.
7. Protein Metabolism
- What it does: Breaks down proteins into amino acids, which can be used to make new proteins or converted into glucose or energy when needed.
8. Photosynthesis (in plants)
- Where it happens: In chloroplasts.
- What it does: Converts light energy into chemical energy (glucose) using carbon dioxide and water.
- Importance: Provides energy and oxygen for all living organisms.
In short:
Major metabolic pathways include glycolysis, Krebs cycle, electron transport chain, beta-oxidation, gluconeogenesis, and glycogen metabolism.
Together, these pathways produce, store, and use energy, keeping the cell — and the entire body — alive and functioning efficiently.