1. Pathways that reduce NAD+ to NADH How do cells transfer electrons from food to NAD+ to make NADH? –From sugars –From proteins –From fatty acids Images are from Wikimedia Commons unless otherwise indicated

2. Oxidation of glucose to CO 2 http://www.biologie.uni-hamburg.de/b-online/e19/19d.htm Glycolysis Pyruvate oxidation Citric acid cycle

3. Glycolysis: partial oxidation of glucose to pyruvate

4. Glycolysis – in cytoplasm of all cells 1.Uses 2 ATPs to “activate” glucose 2.Splits glucose into two 3-carbon sugars 3.Partially oxidizes the sugars, yielding 2 NADH per glucose 4.Substrate-level phosphorylation of ADP to make 4 molecules of ATP 5.Nets 2 pyruvates, 2 ATP, 2 NADH

5. In respiring cells, pyruvate is oxidized to CO 2 + acetyl CoA Two molecules of pyruvate are oxidized to 2 acetyl CoA + 2CO 2, generating 2 NADH per molecule of glucose. http:// www.micro.siu.edu/micr201/chapter8N.html

6. Citric acid cycle generates ATP, reduced electron carriers and oxidizes acetate to CO 2 Campbell & Reece Biology 8 th ed.

8. Fats and proteins http://www.life.umd.edu/classroom/bsci424/BS CI223WebSiteFiles/GeneralCatabolism.gif http://www.ruf.rice.edu/~bioslabs/studies/ mitochondria/mitokrebs.html

9. Locations of eukaryotic energy pathways Campbell & Reece Biology 8 th ed.

10. Respiring cells make most of their ATP via oxidative phosphorylation. What happens in the absence of respiration (no electron transport chain function)?

11. Fermentation reduces pyruvate to lactic acid or ethanol, to regenerate NAD+ from NADH 2 ADP + 2PiPi 2 ATP Glucose Glycolysis 2 NAD + 2 NADH 2 Pyruvate + 2 H + 2 Acetaldehyde 2 Ethanol (a) Alcohol fermentation 2 ADP + 2 PiPi 2 ATP GlucoseGlycolysis 2 NAD + 2 NADH + 2 H + 2 Pyruvate 2 Lactate (b) Lactic acid fermentation 2 CO 2

12. In the absence of respiration Cells can make ATP through glycolysis and fermentation of glucose Cells cannot run pyruvate oxidation or citric acid cycle (no mitochondrial function in eukaryotes)