6O2 + C6H12O6 -> 6CO2 + 6H2O + energy Oxygen + glucose -> carbon dioxide + water + energy

Kreb’s Cycle (Citric Acid Cycle) Regulated by many different enzymes Occurs in mitochondrial matrix A two-carbon compound attached to a co- enzyme enters The carrier/co-enzyme is Coenzyme A

Just ONE ATP molecule. Not enough to live on

Kreb’s Cycle (Citric Acid Cycle) Remember, this… Happens here

Electron Transport Chain

Electron Transport Chain Oxidizes NADH to NAD+ Creates a charged membrane and proton gradient Makes ATP (and heat) Oxygen is the Final Electron Acceptor Without oxygen, you die… and that’s bad The reduced oxygen, with protons, makes water

6O2 + C6H12O6 -> 6CO2 + 6H2O + energy Oxygen + glucose -> carbon dioxide + water + energy

Kreb’s and ETC What do we need to keep ETC going? NADH, FADH2 and Oxygen How/where does NAD+ and FAD+ get ‘recycled’? What do we need to keep the Kreb’s Cycle going?

So, where does the ‘two-carbon compound’ come from?

Glycolysis “First” step in Cellular Respiration Glucose is broken down into 2, 3-carbon molecules Some ATP is made Occurs in cytoplasm/cytosol

Glycolysis- occurs in cytoplasm 3 carbons each

Pyruvic Acid enters mitochondrion Pyruvic Acid is OXIDIZED And a CO2 leaves -> Acetyl-CoA 3 carbons each

Glycolysis Pyruvic Acid vs Pyruvate Two, 3-carbon molecules A TWO-carbon molecule enters the Kreb’s Cycle… A carbon is taken away in between Lost as CO2

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

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?

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

Fermentation If NAD+ is REDUCED to NADH 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! 2 NADH 2 NAD+ 2 Lactate 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 That makes 2 NET ATP Not great, but it helps 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)

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

Lactic Acid – Cori Cycle The liver stores glucose and glycogen Lactic Acid is taken into the blood and carried to the liver How did we get from glucose to lactic acid? In the liver, the process is “reversed” using ATP from aerobic respiration

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

Obj 15 What is the relationship between ‘metabolism’, cellular respiration, energy needs, endothermy and ectothermy? Endotherm – produces its own body heat Ectotherm – relies on environment and behavior for body heat Homeostasis?