Cellular Respiration Overview

Study Notes

Cellular respiration is the primary mechanism cells use to produce energy, primarily ATP
Key processes involve glucose oxidation
Sequential stages, from glycolysis to the electron transport chain, are detailed
Aerobic vs anaerobic respiration (fermentation) differences are highlighted
Mitochondria's role is emphasized, specifically in the citric acid cycle and electron transport chain

Respiration as the Main Source of Cellular Energy: Glucose breakdown produces energy, stored primarily in ATP.
- The overall glucose oxidation reaction is C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy
- Energy is released, with some lost as heat
Sequential Stages of Glucose Oxidation:
- Glycolysis: Cytosol, glucose is split into two pyruvate molecules, yielding 2 ATP and 2 NADH.
- Citric Acid Cycle (Krebs Cycle): Pyruvate is oxidized in the mitochondrial matrix, forming acetyl CoA, and further oxidized in the cycle producing 1 ATP, three NADH, and one FADH₂ molecule per acetyl group (two cycles per glucose molecule).

Essential for respiration, particularly the citric acid cycle and the electron transport chain
Critical processes occur in the inner mitochondrial membrane

Aerobic respiration of one glucose molecule produces approximately 36 ATP molecules
Most ATP is produced in the final stage of respiration, through oxidative phosphorylation in the mitochondria
The inner mitochondrial membrane contains electron carrier proteins

Occurs when oxygen is limited
Pyruvate is converted to lactate or ethanol, producing significantly less ATP (2 ATP per glucose molecule)
This is compared to the much efficient aerobic process

The citric acid cycle is central to catabolism and anabolism
Glucose is the primary substrate, but other molecules (like fats and proteins) can also enter the cycle
Catabolism is the breakdown of organic molecules to release energy; anabolism is the building of cellular components