Chapter 7: Respiration Respiration: 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.

Mitochondrion Inner Space Inner Membrane Outer Membrane Outer Space/ Intermembrane Space

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.

First Stage: Glycolysis 1.Two ATP are invested to rearrange glucose. 2.When glucose is split into two 3-carbon compounds, energy is released. 3.Released energy is stored in 4 ATP (through substrate-level phosphorylation, or direct transfer of phosphate group). 4.NAD+ picks up e- and H+ to become NADH

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

Fig. 8.4c, p. 135 ATP PGAL ATP NADH ATP 2 ATP invested ENERGY-RELEASING STEPS OF GLYCOLYSIS 2 ATP invested NAD + PiPi PiPi 3-phosphoglycerate 2-phosphoglycerate PEP ADP 1,3-bisphosphoglycerate PPPP PP PP PP pyruvate to second set of reactions substrate-level phosphorylation H2OH2O H2OH2O

Second Step: Krebs Cycle 1.Two pyruvate molecules enter the mitochondrion (enter into the inner compartment of mito). 2.Coenzyme-A strips a carbon, yielding CO 2. 3.Acetyl-CoA enters Krebs Cycle/Citric Acid Cycle, yielding more CO 2. 4.Final yield: ATP, NADH, FADH 2.

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

Fig. 8.6, p. 137 oxaloacetate malate citrate isocitrate  -ketogluterate fumarate succinate CoA succinyl–CoA ATP NADH FADH 2 NAD + FAD NAD + CoA H2OH2O H2OH2O H2OH2O ADP + phosphate group (from GTP) KREBS CYCLE PREPARATORY STEPS pyruvate NAD + CoA Acetyl–CoA coenzyme A (CoA) (CO 2 )

Step 3: Electron Transfer Phosphorylation 1.NADH and FADH 2 transfer e- and H+ to inner membrane of mitochondria, buiding up concentration of protons in intermembrane space. 2.When protons flow through ATP synthases, up to 34 ATP are produced. 3.Oxygen will accept extra hydrogens, resulting in water.

Electron Transport Chain

ATP Synthase

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

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

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.

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.