Cellular Respiration: Glycolysis, Krebs Cycle, ATP Yield & Fermentation

Phosphorylation

The addition of a phosphate group to a molecule.

ATP (Adenosine Triphosphate)

An energy-carrying molecule consisting of adenine, a ribose sugar, and three phosphate groups.

Substrate-level phosphorylation

The direct formation of ATP by transferring a phosphate group to ADP (ADP + Pi = ATP).

Oxidative phosphorylation

ATP production linked to redox reactions and the electron transport chain (ADP + Pi = ATP).

OIL RIG

Mnemonic meaning Oxidation Is Loss (of electrons/hydrogen), Reduction Is Gain (of electrons/hydrogen).

Cellular Respiration Inputs

Glucose (enters via facilitated diffusion using carrier proteins) and oxygen (enters via simple diffusion).

Glycolysis Location and Requirement

Occurs in the cytoplasm and does not require oxygen (O2).

Glycolysis Net Yield

Yields a net of 2 ATP and 2 NADH + H+ per glucose molecule (after paying back the 2 ATP used in the first 5 steps).

Pyruvate Oxidation (Acetyl CoA Formation)

A process in the mitochondrial matrix where pyruvate is oxidized into acetyl CoA, losing $CO_2$ and producing NADH + H+ (done twice per glucose).

Krebs (Citric Acid) Cycle Location

mitochondria

Krebs Cycle Yield (Per Two Turns)

Produces 6 NADH + H+, 2 ATP, 2 FADH2, and 4 $CO_2$.

Total Yield Before Electron Transport Chain

10 NADH + H+, 4 ATP, and 2 FADH2 in total from glycolysis, pyruvate oxidation, and the Krebs cycle.

Electron Transport Chain Location

The Mitochondria

Final Electron Acceptor

Oxygen

Cyanide Toxicity

Chokes and cuts off Complex 4 / oxygen, halting the electron transport chain.

Chemiosmosis ATP Breakdown

Converting NADH + H+ back to NAD+ yields 30 ATP, and converting FADH2 back to FAD yields 4 ATP.

Total ATP Yield

38

Fermentation

A method used by some organisms to produce ATP without oxygen while maintaining a constant supply of NAD^

Lactic Acid Fermentation

Pyruvate is converted into lactic acid, converting NADH + H+ back into NAD^+; occurs in low-O2 muscle cells and in making foods like soy sauce and sauerkraut.

Ethanol Fermentation

Pyruvate is converted into acetaldehyde, which is then converted into ethanol and CO_2; used to make beer and champagne.