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ANAEROBIC PATHWAYS . NAD+ is in limited supply, so if the cell does not have a way to oxidize the NADH back to NAD+ glycolysis will come to a halt.
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ANAEROBIC PATHWAYS • NAD+ is in limited supply, so if the cell does not have a way to oxidize the NADH back to NAD+ glycolysis will come to a halt. • The ETC oxidizes NADH to NAD+ when oxygen is present. Eukaryotic organisms have two primary means of oxidizing NADH when oxygen is not present. Bacteria have developed tons of methods. • These processes are called fermentation. • Glycolysis occurs and glucose is broken down into 2 pyruvate, 2 NADH + 2H+, and 2 ATP (net). • Then:
ETHANOL FERMENTATION (yeast cells) • Pyruvate is immediately decarboxylated into acetylaldehyde (CH3COH) • NADH is then oxidized back into NAD+ and the protons (H+) turn acetylaldehyde into ethanol. • Still only a net of 2ATP.
LACTATE FERMENTATION (animal cells) • Pyruvate is immediately reduced by NADH (NADH is oxidized into NAD+) to form lactate • Lactate (lactic acid) is thought to cause muscle pain and stiffness, but current research suggests it is just a correlation • Oxygen debt is the amount of oxygen required to catabolize lactate into carbon dioxide and water. • Lactic acid is transported to the liver and is oxidized back into pyruvate when the oxygen debt is repaid.
VO2 max • The maximum volume of oxygen that the cells of the body can remove from the bloodstream while the body experiences maximal exertion (mL/kg/min) • Measures the body's capacity to generate the energy required for physical activity • Higher VO2 values are associated with higher aerobic fitness (see Table 2 and 3, pg 122) • Average ~35 mL/kg/min, Elite athlete ~70 mL/kg/min • Lab Activity 2.3.4 p. 131 Estimating VO2 max (a less intense, inexpensive way to estimate your VO2 max).