Cellular Respiration Process by which cells extract energy from food Literally it’s about using bond energy (electrons) to regenerate ATP May be anaerobic or aerobic

C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O

Aerobic Respiration as a 3-Act Play Act I: Glycolysis Act II: The Kreb’s Cycle Act III: Oxidative Phosphorylation and the Electron Transport Chain

Glycolysis 6C glucose split to 2, 3C pyruvates Yield 2 ATP Yield 2 NADH 10 reaction steps, each catalyzed by specific enzymes.

What’s the point of glycolysis? The key point of glycolysis is that all cells, without even using oxygen, are able to make food monomers reactive enough to split down to pyruvate. The pyruvate molecules then proceed to further steps that extract much more energy from the bonds.

“The fate of pyruvate” In anaerobic conditions, it is converted to lactic acid or ethanol, with a yield of 4 ATP/glucose In aerobic conditions, it enters the mitochondria, proceeds through Kreb’s Cycle and Oxidative Phosphorylation at the ETC for yield of 36 ATP/glucose

Aerobic Respiration as a 3-Act Play Act I: Glycolysis Act II: The Kreb’s Cycle Act III: Oxidative Phosphorylation and the Electron Transport Chain

Kreb’s Cycle (aka Citric Acid Cycle) A metabolic “furnace” that oxidizes pyruvate fuel. Each pyruvate is broken down to 3 CO 2. 2 pyruvates  2 ATP 6 NADH 2 FADH 2

What’s the point of Krebs Cycle? The point of the Krebs cycle is to reduce coenzymes. In Krebs, NAD+ and FAD are reduced to NADH & FADH 2 from the oxidation of pyruvate (or actually, Acetyl, CoA). The reduced coenzymes, NADH & FADH 2 act as electron taxi cabs, shuttling their key passengers to the cristae.

Mitochondria Anatomy Review Remember: Glycolysis -- in cytosol Krebs -- in mito matrix Ox Phos –at mito cristae (in the “electron transport chain” ETC)

Aerobic Respiration as a 3-Act Play Act I: Glycolysis Act II: The Kreb’s Cycle Act III: Oxidative Phosphorylation and the Electron Transport Chain Chemiosmosis simulationsimulation

Oxidative Phosphorylation and the Electron Transport Chain

What’s the point of oxidative phosphorylation at the ETC? The electrons, originally from glucose, are delivered to the ETC by NADH and FADH 2, and are passed down the ETC. This “electrical energy” runs a molecular machinery that pumps protons across the cristae. These protons pass back through the cristae at the ATP synthase enzyme, regenerating ATP!

Review of Cells & Metabolism Enzymes & Activation Energy ATP and coupled reactions Cellular Respiration –Glycolysis Anaerobic fermentation or lactic acid formation Aerobic, proceed to below –Krebs Cycle –Ox. Phos. & the ETC