Definition: Cellular respiration is a metabolic process that converts biochemical energy from nutrients into ATP (adenosine triphosphate), and then releases waste products.
Main Stages: The process involves several key stages:
Glycolysis
Krebs Cycle
Electron Transport Chain
Glycolysis
Location: Occurs in the cytoplasm of the cell.
Initial Process: Breaks down glucose (C6H12O6) into pyruvate.
Key Outputs:
ATP (net gain of 2 ATP)
NADH (electron carrier)
Pyruvate (converted to Acetyl-CoA for Krebs Cycle)
Krebs Cycle (Citric Acid Cycle)
Location: Takes place in the mitochondrial matrix.
Key Inputs:
Acetyl-CoA
NAD+
FAD
Major Outputs:
NADH
FADH2
2 ATP
Carbon dioxide (CO₂)
Function: Processes pyruvate and generates high-energy electron carriers for the next stage.
Oxidation and Reduction Reactions
Electrons Transfer: Essential for energy production.
Oxidation: Loss of electrons (e-), often resulting in a release of energy.
Reduction: Gain of electrons, resulting in an increase in energy.
Key Concept:
Oxidation is Loss, Reduction is Gain (OIL RIG).
Electron Transport Chain (ETC)
Location: Embedded in the inner mitochondrial membrane.
Function:
Receives high-energy electrons from NADH and FADH2.
Establishes a proton (H+) gradient across the inner mitochondrial membrane.
Process:
Electrons are transferred through protein complexes, moving to lower energy states.
Energy released is used to pump protons into the intermembrane space.
H+ ions flow back into the mitochondrial matrix through ATP synthase, generating ATP (chemiosmosis).
ATP Synthase
Function: Enzyme that synthesizes ATP from ADP and inorganic phosphate (Pi) using the proton gradient.
Process: As protons flow through, ATP synthase rotates and catalyzes ATP formation.
Net ATP Yield: Approximately 32 ATP molecules produced per glucose molecule during aerobic respiration.