Cellular Respiration Overview

Cellular Respiration Overview

• Cellular respiration is the process of breaking down glucose to produce ATP (energy).
• Aerobic respiration requires oxygen, producing 30-38 ATP molecules per glucose molecule.
• Anaerobic respiration (fermentation) occurs without oxygen, only glycolysis occurs producing a low amount of ATP (2 ATP).

Stages of Cellular Respiration

• Glycolysis: Occurs in the cytoplasm, glucose is broken down into 2 pyruvate molecules. Produces 2 ATP, 2 NADH, occurs in both aerobic and anaerobic respiration.
• Pyruvate Oxidation (Preparatory Reaction): Occurs in the mitochondrial matrix, pyruvate is converted to Acetyl CoA. Produces 2 NADH and releases CO2.
• Citric Acid Cycle (Krebs Cycle): Occurs in the mitochondrial matrix, acetyl CoA enters the cycle, releasing CO2 and producing ATP, NADH, and FADH2.
• Electron Transport Chain (ETC) and Chemiosmosis: Occurs in the inner mitochondrial membrane, electrons from NADH and FADH2 are passed down a chain, generating a proton gradient. ATP synthase uses this gradient to produce a large amount of ATP (30-38). Oxygen is the final electron acceptor, forming water.

Reactants and Products

• Aerobic: Reactants: Glucose and Oxygen. Products: Carbon dioxide, Water, and 30-38 ATP.
• Anaerobic: Reactants: Glucose. Products: Lactic acid (animals) or ethanol and carbon dioxide (yeast), and 2 ATP.

Locations

• Glycolysis: Cytoplasm
• Pyruvate Oxidation: Mitochondrial Matrix
• Citric Acid Cycle: Mitochondrial Matrix
• Electron Transport Chain: Inner Mitochondrial Membrane

ATP Synthase

• Enzyme that generates ATP during the electron transport chain
• Uses the proton gradient to catalyze ATP production

Mitochondria

• The powerhouses of the cell, where cellular respiration takes place in eukaryotes.
• Double membrane structure.
• Matrix (inner compartment): Location of Krebs cycle and pyruvate oxidation.
• Cristae: Infoldings of the inner membrane that increase surface area for the ETC.
• Intermembrane space: the space between the outer and inner membranes, where the proton gradient is established for ATP production.

Importance of Oxygen

• Oxygen is the final electron acceptor in the electron transport chain.
• Without oxygen, cellular respiration cannot proceed efficiently, and cells resort to anaerobic respiration (fermentation). This yields much less energy.