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Cellular Respiration Glycolysis Glucose 2 NAD+ “2” ATP 2 NADH 4 ATP 2 PyruvateAcetyl- CoA Coenzyme A CO2 Kreb’s Cycle 2-carbons NADH FADH2 CO2 ETC 32 ATP! water heat O2

What if… You’re working out? Your muscles’ ATP demand increases But ‘you’ can only supply finite oxygen… For instance, a muscle cell needs 1200 ATP per second, but the ETCs can only supply 1000 What happens?

Cellular Respiration Glycolysis Glucose 2 NAD+ “2” ATP 2 NADH 4 ATP 2 PyruvateAcetyl- CoA Coenzyme A CO2 Kreb’s Cycle 2-carbons NADH FADH2 CO2 ETC 32 ATP! water heat O2 What do we need to keep THIS going? NAD+ is …? To keep this going we need to...?

Fermentation 1.If NAD+ is REDUCED to NADH 2.Then we need to OXIDIZE it back to NAD+ Glucose 2 NAD+ “2” ATP 2 NADH 4 ATP 2 Pyruvate

Fermentation If NAD+ is REDUCED to NADH Then we need to OXIDIZE it back to NAD+ In the ETC, Oxygen takes the electrons We don’t have enough oxygen, so we need to find something to take the electrons from NADH to make it NAD+

Fermentation Pyruvate can do that! Glucose 2 NAD+ “2” ATP 2 NADH 4 ATP 2 Pyruvate 2 Lactate (Lactic Acid)

Fermentation During Glycolysis, NAD+ is REDUCED to NADH (the two, 3-carbon molecules are oxidized)

Fermentation During Glycolysis, NAD+ is REDUCED to NADH (the two, 3-carbon molecules are oxidized) In fermentation, then we need to OXIDIZE it back to NAD+, so Pyruvate is REDUCED and forms lactic acid This LOWERS your muscle pH and causes ‘fatigue’ because your muscles don’t function as well at lower pH

By Oxidizing NADH back to NAD+, Glycolysis can keep going Glucose 2 NAD+ “2” ATP 2 NADH 4 ATP 2 Pyruvate 2 Lactate (Lactic Acid) That makes 2 NET ATP Not great, but it helps

Fermentation Lactic Acid fermentation keeps glycolysis going and that makes some ATP (without needing Kreb’s and ETC) This decreases pH and reduces cells’ ability to function Also, the cells/body go in to Oxygen Debt. You ‘borrowed’ to make ATP, now you have to pay it back With Oxygen

Fermentation This process can happen REALLY fast It’s a ‘good’ source of quick ATP NO oxygen needed

Fermentation NO oxygen needed Anaerobic Takes place in cytoplasm of cell

Fermentation No ATP are ‘produced’ during fermentation So why do cells do it? It makes NAD+, which keeps Glycolysis going THAT produces ATP

Homework Read Section 9.3; questions at end of section