Metabolism Basics
Metabolism is the set of chemical reactions that turn food into usable energy and the parts your body needs.
- Two sides: Catabolism breaks molecules to release energy; anabolism builds new molecules.
- ATP: Cells convert food energy into ATP, the “spendable” energy form.
- Enzymes: Protein helpers that make reactions fast and controlled.
- Mitochondria: Main ATP makers when oxygen is available.
- Even at rest: Your BMR (basal metabolic rate) powers heartbeat, breathing, brain work, and body temperature.
Fuel Pathways
Your body changes fuel and speed depending on activity level, oxygen, and biology.
- Fuel choices: Carbs → glucose (fast fuel), fats → fatty acids (lots of energy, slower), proteins → amino acids (mainly building, backup fuel).
- With oxygen (aerobic): Mitochondria make lots of ATP, which is best for steady efforts (e.g., a jog) or long practice.
- Low oxygen (anaerobic): Quick ATP with lactate—best for short bursts (a sprint).
- What sets “speed”: Muscle mass, training (more mitochondria), hormones (especially thyroid), sleep, and age all shift metabolic rate.
Fun Facts
Here are some interesting facts about metabolism:
- Hummingbirds burn fuel so fast their hearts can beat >1,000 times per minute.
- Hibernating bears drop their metabolism to survive months with almost no food.
- Babies have brown fat that burns energy to make heat.
- The glow of fireflies comes from an ATP-powered enzyme reaction.
Review
Let’s quickly recap what we learned about metabolism:
- What do we call breaking molecules down to release energy? Catabolism
- What do we call building new molecules from smaller ones? Anabolism
- Which cell organelle produces the most ATP during aerobic respiration? Mitochondria
- What do we call the proteins that speed up chemical reactions? Enzymes
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