Metabolism is the total set of chemical reactions that keeps a cell alive. It controls how nutrients are broken down, how energy is captured, and how new molecules are built. Understanding metabolism helps explain growth, movement, body temperature, digestion, and why cells need a steady supply of fuel and oxygen.
The main idea is that matter is rearranged while energy is transferred between molecules.
Key Facts
- Metabolism = catabolism + anabolism.
- Catabolism breaks large molecules into smaller molecules and often releases energy.
- Anabolism builds larger molecules from smaller molecules and requires energy input.
- ATP + H2O -> ADP + Pi + energy releases usable energy for cell work.
- ADP + Pi + energy -> ATP stores energy in a phosphate bond.
- Cellular respiration summary: C6H12O6 + 6O2 -> 6CO2 + 6H2O + ATP.
Vocabulary
- Metabolism
- Metabolism is the complete network of chemical reactions that transform matter and energy in an organism.
- Catabolism
- Catabolism is the set of pathways that break down molecules and release energy.
- Anabolism
- Anabolism is the set of pathways that build complex molecules using energy and smaller building blocks.
- ATP
- ATP, or adenosine triphosphate, is the main energy-carrying molecule used to power cellular processes.
- Enzyme
- An enzyme is a biological catalyst that speeds up a specific chemical reaction without being used up.
Common Mistakes to Avoid
- Thinking catabolism only destroys molecules is wrong because catabolic pathways also capture useful energy in ATP and electron carriers.
- Thinking anabolism releases energy is wrong because building large, ordered molecules usually requires an input of ATP or reducing power.
- Treating ATP as long-term energy storage is wrong because ATP is a short-term energy transfer molecule, while fats and carbohydrates store energy for longer periods.
- Ignoring enzymes is wrong because most metabolic reactions would be too slow for life without enzyme-catalyzed pathways.
Practice Questions
- 1 A cell uses 18 ATP molecules to build a protein and 7 ATP molecules to synthesize lipids. How many ATP molecules are used in total for these anabolic processes?
- 2 During a period of exercise, muscle cells produce 96 ATP from glucose breakdown. If each glucose molecule yields 32 ATP, how many glucose molecules were broken down?
- 3 Explain why catabolic and anabolic pathways are connected through ATP rather than operating as completely separate systems.