Cellular respiration is the process by which cells break down macromolecules, like glucose, to produce ATP, the energy currency of the cell.
This overview covers the three main steps: Glycolysis, the Krebs cycle (Citric Acid Cycle), and the Electron Transport Chain (Oxidative Phosphorylation).
Glycolysis
Location: Cytosol
Process:
Starts the process of energy extraction from glucose.
Requires input of a glucose and two ATP molecules.
Outputs:
4 ATP (Net gain of 2 ATP)
2 NADH
2 Pyruvate molecules
Pyruvate Oxidation
Process:
Converts 2 pyruvate molecules to 2 acetyl CoA molecules.
Produces 2 NADH.
Krebs Cycle (Citric Acid Cycle)
Location: Mitochondria
Process:
Each acetyl CoA goes through the cycle separately.
For each acetyl CoA:
Produces 3 NADH
Produces 1 FADH2
Produces 1 ATP or GTP
Total Production (for both acetyl CoA):
6 NADH
2 FADH2
2 ATP
Electron Transport Chain (Oxidative Phosphorylation)
Location: Mitochondria
Process:
Uses NADH and FADH2 to create a concentration of hydrogen ions and an electrochemical gradient.
High concentration of hydrogen ions powers ATP production via ATP synthase.
ATP Yield:
2.5 ATP per NADH
1.5 ATP per FADH2
Total ATP Production from One Glucose Molecule
10 NADH:
2 from Glycolysis
2 from Pyruvate Oxidation
6 from Krebs Cycle
Yields approximately 25 ATP
2 FADH2 from Krebs Cycle:
Produces 3 ATP
4 ATP from Glycolysis and Krebs Cycle:
Total of 32 ATP from one glucose
Note: Theoretical yield is 38 ATP, but actual yield ranges between 30 and 32 ATP due to cellular conditions.
Additional Resources
Links for detailed videos on each step will be available.
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