Chapter 7 Glycolysis and the Citric Acid Cycle

You Must Know  NAD+ and NADH  The role of glycolysis in oxidizing glucose to two molecules of pyruvate.  How pyruvate is moved from the cytosol into the mitochondria and introduced into the citric acid cycle.  That the citric acid cycle oxidizes organic molecules to produce NADH and FADH 2

Figure 7.UN03 Respiration becomes oxidized becomes reduced For each molecule of glucose degraded to CO 2 and water by respiration, the cell makes up to 32 molecules of ATP

NAD  Nicotinamide (oxidized form) Nicotinamide (reduced form) Oxidation of NADH Reduction of NAD  Dehydrogenase NADH  2[H] (from food) 2 e −  2 H  2 e −  H  HH HH  During respiration, electrons from organic compounds are usually first transferred to NAD  Reduced form Oxidized form

Electrons via NADH Glycolysis GlucosePyruvate oxidation Acetyl CoA Citric acid cycle Electrons via NADH and FADH 2 Oxidative phosphorylation: electron transport and chemiosmosis CYTOSOL ATP Substrate-level ATP Substrate-level MITOCHONDRION ATP Oxidative Overview of cellular respiration

Electrons via NADH Glycolysis GlucosePyruvate CYTOSOL ATP Substrate-level MITOCHONDRION Net gain of 2 ATP Glycolysis occurs whether or not O 2 is present.

Substrate-level phosphorylation Substrate P ADP Product ATP  Enzyme

Energy Investment Phase Energy Payoff Phase Net Glucose 2 ADP  2 P 4 ADP  4 P 2 NAD   4 e −  4 H  4 ATP formed − 2 ATP used 2 ATP 4 ATP used formed 2 NADH  2 H  2 Pyruvate  2 H 2 O 2 NADH  2 H  2 ATP Glycolysis

Figure Electrons via NADH Glycolysis GlucosePyruvate oxidation Acetyl CoA Citric acid cycle Electrons via NADH and FADH 2 CYTOSOL ATP Substrate-level ATP Substrate-level MITOCHONDRION

Figure 7.10 CYTOSOL Pyruvate (from glycolysis, 2 molecules per glucose) CO 2 CoA NAD  NADH MITOCHONDRION CoA Acetyl CoA  H  In the presence of O 2, pyruvate enters the mitochondrion (in eukaryotic cells). Pyruvate is oxidized

Figure 7.10b CoA Citric acid cycle FADH 2 FAD ADP  P i ATP NADH 3 NAD  3  3 H  2CO 2 CoA Acetyl CoA Citric Acid Cycle All along the citric acid cycle organic molecules are oxidized and NAD + is reduced to become NADH and FAD is reduced to become FADH 2. The NADH and FADH 2 produced by the cycle relay electrons extracted from food to the electron transport chain.