Mitochondrion

1. Chapter 7: RespirationRespiration: The release of stored energy (sugar). Usually involves oxygen (the reason we breath is to release energy from our food).Aerobic vs Anaerobic: Aerobic means in the presence of oxygen.

2. Mitochondrion Inner Membrane Outer Membrane Outer Space/ Intermembrane Space Inner Space

3. First Stage: Glycolysis BASICS: Glycolysis doesn’t require oxygen (anaerobic)! Glycolysis doesn’t occur in the mitochondria, so it can happen in prokaryotes (lacking organelles). Glycolysis occurs in the cytoplasm. Glycolysis begins with glucose and ends with two pyruvate molecules, yielding minimal energy gain.

4. First Stage: Glycolysis • Two ATP are invested to rearrange glucose. • When glucose is split into two 3-carbon compounds, energy is released. • Released energy is stored in 4 ATP (through substrate-level phosphorylation, or direct transfer of phosphate group). • NAD+ picks up e- and H+ to become NADH

5. ENERGY-REQUIRING STEPS OF GLYCOLYSIS glucose ATP 2 ATP invested ADP P glucose-6-phosphate P fructose-6-phosphate ATP ADP P fructose-1,6-bisphosphate (see next slide) Fig. 8.4b, p. 135

6. ENERGY-RELEASING STEPS OF GLYCOLYSIS PGAL PGAL NAD+ NAD+ NADH NADH Pi Pi P P P P 1,3-bisphosphoglycerate 1,3-bisphosphoglycerate substrate-level phosphorylation ATP ATP 2 ATP invested P P 3-phosphoglycerate 3-phosphoglycerate P P 2-phosphoglycerate 2-phosphoglycerate H2O H2O P P PEP PEP substrate-level phosphorylation ADP ADP ATP ATP 2 ATP invested pyruvate pyruvate Fig. 8.4c, p. 135 to second set of reactions

8. Second Step: Krebs Cycle • Two pyruvate molecules enter the mitochondrion (enter into the inner compartment of mito). • Coenzyme-A strips a carbon, yielding CO2. • Acetyl-CoA enters Krebs Cycle/Citric Acid Cycle, yielding more CO2. • Final yield: ATP, NADH, FADH2.

9. 1 Pyruvate from cytoplasm inters inner mitochondrial compartment. OUTER COMPARTMENT 4 As electrons move through the transport system, H+ is pumped to outer compartment. NADH 3 NADH and FADH2 give up electrons and H+ to membrane-bound electron transport systems. acetyl-CoA NADH Krebs Cycle NADH ATP ATP 5 Oxygen accepts electrons, joins with H+ to form water. ATP 2 Krebs cycle and preparatory steps: NAD+ and FADH2 accept electrons and hydrogen stripped from the pyruvate. ATP forms. Carbon dioxide forms. ATP free oxygen ADP + Pi INNER COMPARTMENT 6 Following its gradients, H+ flows back into inner compartment, through ATP synthases. The flow drives ATP formation. Fig. 8.5b, p. 136

10. PREPARATORY STEPS pyruvate coenzyme A (CoA) NAD+ (CO2) NADH CoA Acetyl–CoA KREBS CYCLE CoA oxaloacetate citrate H2O NADH H2O NAD+ isocitrate malate NAD+ H2O NADH fumarate a-ketogluterate FADH2 CoA NAD+ FAD NADH succinate CoA succinyl–CoA Fig. 8.6, p. 137 ADP + phosphate group (from GTP) ATP

12. Step 3: Electron Transfer Phosphorylation • NADH and FADH2 transfer e- and H+ to inner membrane of mitochondria, buiding up concentration of protons in intermembrane space. • When protons flow through ATP synthases, up to 34 ATP are produced. • Oxygen will accept extra hydrogens, resulting in water.

13. Electron Transport Chain

14. ATP Synthase

15. 1 Pyruvate from cytoplasm inters inner mitochondrial compartment. OUTER COMPARTMENT 4 As electrons move through the transport system, H+ is pumped to outer compartment. NADH 3 NADH and FADH2 give up electrons and H+ to membrane-bound electron transport systems. acetyl-CoA NADH Krebs Cycle NADH ATP ATP 5 Oxygen accepts electrons, joins with H+ to form water. ATP 2 Krebs cycle and preparatory steps: NAD+ and FADH2 accept electrons and hydrogen stripped from the pyruvate. ATP forms. Carbon dioxide forms. ATP free oxygen ADP + Pi INNER COMPARTMENT 6 Following its gradients, H+ flows back into inner compartment, through ATP synthases. The flow drives ATP formation. Fig. 8.5b, p. 136

16. Possible Pathways Glucose Glycolysis (no oxygen, for muscle) Lactate Fermentation (no oxygen for yeast, bacteria) Alcoholic Fermentation (if oxygen) Aerobic Respiration (in mitochondria)

17. Alcoholic Fermentation (anaerobic) If no oxygen is available, only glycolysis can occur. In this case, pyruvate doesn’t enter the mitochondrion but rather is modified in the cytoplasm. The result is ethanol and carbon dioxide. Very little energy release as compared to aerobic respiration, so not an option for large, active animals.

18. Lactic Acid Fermentation (anaerobic) If no oxygen is available, only glycolysis can occur. In this case, pyruvate doesn’t enter the mitochondrion but rather is modified in the cytoplasm. The result is lactate. Very little energy release as compared to aerobic respiration, so only used for short bursts of energy.