SECTION 3: MITOCHONDRIA & KREBS CYCLE

Mitochondria – Intermembrane Space

Space between the outer and inner membranes. H⁺ (protons) accumulate here to create a gradient that drives ATP synthesis via chemiosmosis.

Mitochondria – Inner Membrane / Cristae

Folded inner membrane. Location of the Electron Transport System (ETS) and F₀F₁-ATP synthase. Folds (cristae) increase surface area.

Mitochondria – Matrix

Interior fluid of the mitochondria. Location of the Krebs Cycle. Contains enzymes, DNA, and ribosomes.

Krebs Cycle – Location

Mitochondrial matrix

Krebs Cycle – Starting Materials

Acetyl CoA (2C) + Oxaloacetate (4C) → Citrate (6C). Required oxidizers: NAD⁺ and FAD.

Krebs Cycle – End Products (per turn)

3 NADH, 1 FADH₂, 1 ATP (substrate-level), 2 CO₂. Oxaloacetate is regenerated.

Krebs Cycle – Scorecard (per glucose = 2 turns)

6 NADH, 2 FADH₂, 2 ATP, 4 CO₂ released.

Krebs Cycle – Control (ON)

Turned ON by ADP, NAD⁺, FAD — low energy signals indicating the cell needs more ATP.

Krebs Cycle – Control (OFF)

Turned OFF by ATP, NADH, FADH₂ — high energy signals indicating the cell has enough ATP.

Amino Acids → Krebs Cycle

Amino acids can be deaminated (NH₂ removed) and converted into Krebs intermediates (e.g. pyruvate, α-ketoglutarate, oxaloacetate) to provide energy.