Chapter 8 - Cellular Respiration

Summary of glucose metabolism

• review of energy in ecosystems

• photosynthesis and aerobic respiration are linked to each other

• carbon dioxide + water + sunlight energy ---------> glucose + oxygen

• glucose + oxygen ---------> carbon dioxide + water + chemical energy (ATP) + heat energy

2 Pathways for releasing energy from glucose

1. aerobic respiration

2. anaerobic respiration (fermentation)

Glucose breakdown - Step 1 - Glycolysis

• occurs in the cytoplasm of all cells

• glucose is split apart into pyruvate

• some energy is released as ATP and NADH

Fate of pyruvate - Fermentation

• if there's no oxygen (anaerobic respiration)

• occurs in the cytoplasm

• does not make ATP; it turns NADH back into NAD⁺

• pyruvate is converted to lactate

• pyruvate is converted to ethanol and carbon dioxide

Fate of pyruvate - Citric Acid Cycle

• if there's oxygen (aerobic respiration)

• occurs in the mitochondria's matrix

• pyruvate is broken into carbon dioxide

• more energy is released as ATP and NADH (carries high energy electrons)

Electron transport and ATP production

• occurs in the mitochondria's inner membrane

• the electrons carried by NADH are given to an electron transport chain

• as the electrons are passed along, they are used to do work (pumping H⁺)

• oxygen catches the electrons at the end of the chain forming water

• as H⁺ move back across the membrane, they make lots of ATP

Summary of glucose breakdown

• no oxygen: glycolysis + fermentation = 2 ATP

• oxygen: glycolysis + cellular respiration = 36 ATP

© Carol L. Wymer, 2004