Aerobic Respiration Overview
Aerobic respiration is a multistep process that releases energy from respiratory substrates using oxygen. This page covers the initial stages of respiration, including glycolysis and the link reaction.
Glycolysis
Glycolysis is the first process in both aerobic and anaerobic respiration, occurring in the cytoplasm.
Definition: Glycolysis is the splitting of glucose into two pyruvate molecules, producing a net gain of 2 ATP and 2 NADH.
The process involves phosphorylation of glucose and results in:
• 2 pyruvate molecules
• 2 NADH molecules
• Net production of 2 ATP molecules
The Link Reaction
Following glycolysis, the link reaction converts pyruvate to acetyl-CoA.
Highlight: The link reaction connects glycolysis to the Krebs cycle by producing acetyl-CoA, which enters the cycle.
Key points of the link reaction:
• Occurs when oxygen is present (aerobic conditions)
• Converts pyruvate to acetyl, which binds to Coenzyme A
• Produces NADH and CO₂
Anaerobic Respiration
When oxygen concentration is low, cells can still produce some ATP through anaerobic respiration.
Example: In mammals, pyruvate is converted to lactate during anaerobic conditions, allowing glycolysis to continue.
Anaerobic respiration in different organisms:
• Mammals: Pyruvate → Lactate
• Yeast and plants: Alcoholic fermentation (Pyruvate → Ethanal → Ethanol)
The Krebs Cycle
The Krebs cycle, also known as the citric acid cycle, is a series of reactions that complete the oxidation of glucose.
Vocabulary: Substrate-level phosphorylation - the production of ATP by direct transfer of a phosphate group from a substrate to ADP.
Key points of the Krebs cycle:
• Occurs twice for each glucose molecule
• Produces 4 CO₂, 6 NADH, 2 FADH₂, and 2 ATP per glucose
• ATP is produced via substrate-level phosphorylation
