Respiration

Concepts

• Respiration is a catabolic process used to extract energy from food to do cellular work.
• Aerobic respiration requires oxygen.       Blank aerobic respiration diagram.
• Anaerobic respiration does not need oxygen.

Aerobic Respiration

• Converts food energy (glucose) into cellular energy (ATP)
• C₆H₁₂O₆   +   6 O₂ 6 CO₂   +   6 H₂O
• 38% efficient
• Three stages to aerobic respiration

Glycolysis

• Occurs in cytosol.
• One 6-carbon glucose reduced to two 3-carbon pyruvate.
• Net gain of two ATP and two electron carriers.
• Retained in all living organisms.

Krebs cycle

• Occurs in mitochondria.
• One pyruvate reduced to three CO₂, an ATP and five electron carriers.
• Takes two turns of cycle to process remains of one glucose.
• So total yield is six CO₂, two ATP and ten electron carriers!

Electron Transport Chain

• Occurs in mitochondria.
• Energy of electron cascade is used to pump protons (H+)!
• Used electrons are passed to oxygen. Oxygen reduced to form water.
• H+ reentering inner mitochondrion membrane phosphorylate ADP.
• Gain of 32 ATP.

Some of the Players

• ATP
• Pyruvate
• Electron carriers:
  • NAD+ (nicotinamide adenine dinucleotide) : cofactor molecule that acts as electron carrier.
  • NADH : reduced form of NAD+.
  • FAD+ (flavin adenine dinucleotide) : membrane-bound electron carrier.
  • FADH₂ (flavin adenine dinucleotide) : reduced FAD+
  • Acetyl-CoA : acetyl group with coenzyme-A carrier molecule.