SECTION 1: GLYCOLYSIS & FATE OF PYRUVATE

Glycolysis – Starting Material

1 glucose (6C)

Glycolysis – End Products

2 pyruvate (3C each)

Glycolysis – Location

Cytoplasm (cytosol)

Glycolysis – ATP Scorecard

2 ATP invested, 4 ATP produced = 2 NET ATP; also produces 2 NADH

Glycolysis – Required Oxidizer

NAD⁺ → NADH

Substrate-Level Phosphorylation

ATP made directly when a phosphate is transferred from a substrate to ADP. Occurs in the cytoplasm (glycolysis) and mitochondrial matrix (Krebs cycle).

Oxidative Phosphorylation

ATP made using energy from the electron transport system (ETS). Occurs at the inner mitochondrial membrane.

Fate of Pyruvate – With Oxygen

Pyruvate → Acetyl CoA → enters Krebs Cycle in the mitochondria. End products: CO₂, H₂O, ATP.

Fate of Pyruvate – No Oxygen (Muscle)

Lactic acid fermentation. Pyruvate → lactic acid. Regenerates NAD⁺ so glycolysis can keep running.

Fate of Pyruvate – No Oxygen (Yeast)

Alcoholic fermentation. Pyruvate → ethanol + CO₂. Regenerates NAD⁺ so glycolysis can keep running.

Why does fermentation occur?

To regenerate NAD⁺ so glycolysis can continue producing ATP when oxygen is not available.

Lactic Acid & Oxygen Debt

Lactic acid builds up in muscle during intense exercise causing fatigue. Oxygen debt = extra O₂ needed after exercise to convert lactate back to glucose.

Cori Cycle

Lactate travels via blood from muscle to the liver → liver converts it back to glucose via gluconeogenesis → glucose returns to muscle.

Gluconeogenesis

Making NEW glucose from non-carbohydrate sources (lactate, amino acids, glycerol). Occurs in the liver.

Glycogenolysis

Breaking down stored glycogen to release glucose. Occurs in liver and muscle.

Glycogenesis

Building glycogen from glucose for storage. Occurs in liver and muscle.