Cellular Respiration: Stages and Processes

Cellular Respiration

• Cellular respiration is a chemical process that releases energy from organic compounds (food), converting it into energy stored in ATP molecules.

Breathing versus Cellular Respiration

• Breathing is a physical process that allows animals and humans to come into contact with gases in the air.
• Cellular respiration is a chemical process that releases energy from food, converting it into energy stored in ATP molecules.

Chemical Pathways

• Cells use food to synthesize new molecules to carry out life processes.
• Cells do not burn glucose; they slowly release energy from it and other food compounds through several pathways.

Overview of Cellular Respiration

• In the presence of oxygen, glycolysis is followed by the Krebs cycle and electron transport chain.
• The three stages combined make up cellular respiration, releasing energy by breaking down food molecules in the presence of oxygen.
• The equation for cellular respiration is: 6O2 + C6H12O6 → 6CO2 + 6H2O + energy (ATP).

Glycolysis

• Glycolysis is the first stage of cellular respiration, releasing a small amount of energy (2 net ATP).
• If oxygen is present, glycolysis leads to the Krebs cycle and electron transport chain; if oxygen is absent, it leads to fermentation.

Mitochondria

• Mitochondria have three compartments: intermembrane space, cristae space, and matrix.
• They play a crucial role in aerobic respiration.

Aerobic Respiration: The Krebs Cycle and Electron Transport

• The Krebs cycle is the second stage of cellular respiration, breaking down pyruvic acid into carbon dioxide in a series of energy-extracting reactions.
• The Krebs cycle requires oxygen and produces ATP, NADH, and FADH2.
• Electron transport uses the high-energy electrons from NADH and FADH2 to produce a large amount of ATP.

Fermentation

• Fermentation is an anaerobic process that occurs in the absence of oxygen.
• There are two types of fermentation: alcoholic fermentation and lactic acid fermentation.
• Lactic acid fermentation is used by humans.

Comparison of Aerobic and Anaerobic Respiration

• Aerobic respiration is far more energy-efficient than anaerobic respiration.
• Aerobic processes produce up to 38 ATP per glucose, while anaerobic processes yield only 2 ATP per glucose.