Citric Acid Cycle Notes

Second step of cellular respiration.
Pyruvate from glycolysis enters mitochondria and is oxidized in the citric acid cycle.
Generates ATP.

Glycolysis: Glucose is oxidized to pyruvate in the cytoplasm, yielding a net of 2 ATP and NADH.
Pyruvate enters the mitochondria via transport protein.
Pyruvate oxidation: Pyruvate loses a molecule of carbon dioxide and is converted to acetyl coenzyme A.
NAD+ is reduced to NADH.
Acetyl coenzyme A (two-carbon molecule) enters the citric acid cycle.

Cycle starts with oxaloacetate and regenerates it.
Acetyl coenzyme A (2C) combines with oxaloacetate (4C) to form citrate (6C).
Citrate loses and gains water to form isocitrate (6C).
Isocitrate forms alpha-ketoglutarate (5C), losing carbon dioxide and reducing NAD+ to NADH.
Alpha-ketoglutarate loses another carbon dioxide, adds coenzyme A, forming succinyl coenzyme A (4C).
Succinyl coenzyme A loses coenzyme A to form succinate (4C), generating ATP or GTP.
Succinate forms fumarate (4C), reducing FAD to FADH2.
Fumarate adds water to form malate (4C).
Malate is converted back to oxaloacetate, reducing NAD+ to NADH.

Per pyruvate molecule: 1 ATP, 3 NADH, and 1 FADH2 are produced.
Per glucose molecule (two pyruvates): 2 ATP, 6 NADH, and 2 FADH2 are produced.
NADH and FADH2 are electron carriers for ATP synthesis via the electron transport chain.
Input: Pyruvate from cytosol to mitochondria.
Outputs: ATP, NADH, and FADH2.