Cellular Metabolism

How do cells obtain energy from food?

A. Types of metabolism

1. Autotrophs
   1. Absorption of nutrients
   2. Photosynthesis
2. Heterotrophs
   1. Digestion
   2. Transport
   3. Cellular Respiration
   4. Fermentation
3. Metabolism in ecosystems
   1. Consumers
   2. Producers

B. How cells produce energy

1. Digestion of food
   • Enzymes!
   1. Protein
   2. Fats
   3. Carbohydrates
      • Which of these gives you the most energy?
2. Transporting food into the cell
   1. Facilitated diffusion
   2. Phagocytosis
3. Cellular Respiration
   • "Burning food": C6H12O6 + 6O2 = 6CO2 + 6H2O
   • What does "respiration" have to do with "breathing"?

   Step 1: Glycolysis

   1. Occurs in cytoplasm
   2. Produces 2 pyruvate + 2 ATP

   Step 2: Krebs cycle

   1. Occurs in mitochondria
   2. Uses pyruvate, makes CO2

   Step 3: Electron Transport Chain

   1. Occurs in mitochondria
   2. Uses electron flow to make ATP
   3. Where do all the electrons come from?
      • Electron carriers: Coenzymes
4. Fermentation: When you're not using oxygen
   • The overworked muscle
   • The versatile yeast cell
   1. Glycolysis does not use oxygen
   2. Glycolysis gives off 2 ATP
   3. Pyruvate becomes a waste material
      • Lactic acid
      • Ethanol
      • Acetone
   4. Fermentation is used to make:
5. Unusual metabolism: The world of prokaryotes
   1. Life without oxygen: Strict anaerobes
   2. Facultative anaerobes can do it all
   3. Bacteria that live on ammonia, methane, or sulfur

Applications

1. Nutrition and calories
2. Exercise - feeling the burn
3. Alcohol, dairy and bread production
4. Life on the early Earth: The worst case of environmental poisoning