Chapter 13 How Cells Obtain Energy From Food Essential Cell Biology FOURTH EDITION Copyright © Garland Science 2014 Alberts Bray Hopkin Johnson Lewis Raff Roberts Walter

Enzymes Allow Energy to be Extracted from Food in Discrete Steps and Stored in Activated Carrier Molecules Fig ATP NADH

Fig Catabolism Occurs in Three Stages

Overview of Glycolysis Fig. 13-4

Fig A little more detail…. ATP consumed Set up for ATP production exceeding ATP consumption NADH production (NAD + regenerated by ETC of mitochondria in aerobic organisms)

NAD + regenerated by fermentation in anaerobic cells Fig. 13-6

Skeletal muscles contain both aerobic slow twitch and anaerobic fast twitch muscle fibers. fast slow Karp,CMB7 slow twitch: long duration, low intensity contractions (+ mitochondria) fast twitch: short duration, high intensity contractions (- mitochondria)

Step 6Step 7 Focus on Steps Producing NADH and ATP Panel 13-1  G = +1.5  G = Combined  G = - 3.0

Fig High-Energy Bond Created in Step 6 Provides Energy for ATP Synthesis in Step 7 can be used in OxPhos substrate level phosphorylation

Step 6: -short-lived high energy thioester bond formed between Cys of enzyme and substrate -electrons transferred from substrate to NAD + -high energy Pi bond displaces high energy thioester bond linking substrate to enzyme Step 7: -high energy Pi transferred to ADP in ATP synthesis by substrate-level phosphorylation Fig. 13-9a Details of High Energy Bond

Fig-139b Steps 6 & 7 Generate Products for ATP Synthesis by Two Mechanisms

Phosphate Bonds with Higher Energy Than Those in ATP Can Be Used to Produce ATP by Substrate-Level Phosphorylation Step 7 Step 10 Fig energy investment: step 1 creatine phosphate (~10.0) stored in muscle

Step 10 Also Involves Substrate-Level Phosphorylation Panel 13-1

Pyruvate Converted to Acetyl CoA and CO2 by Pyruvate Dehydrogenase in Mitochondria large complex contains multiple copies of enzymatic subunits 1 and 3 tethered to core subunit 2 Fig

Fig Citric Acid Cycle NADH used in ATP synthesis by OxPhos Fats also enter cycle as acetyl-CoA.

Electron transport generates H + gradient during Oxidative Phosphorylation Fig IMMOMM matrix ATP and NADH activated carriers produced

Two Other Activated Carriers Produced in Citric Acid Cycle GTP (ATP equivalent) FADH 2 e - carrier Fig produced by SDH embedded in IMM

Krebs Used SDH Inhibitor to Show Pathway is Cyclical x Malonate Inhibits SDH Step Fig

Addition of either A-D or F-H caused accumulation of E (Succinate) during inhibition. Fig

Glycolysis and Citric Acid Cycle Also Provide Entry Points to Anabolic Pathways Fig also provide entry points for other C sources for catabolism

Big Picture of Metabolic Pathways in Cells Glycolysis and Citric Acid Cycle in Red Fig

Regulating Catabolism vs. Anabolism: allosteric modulation of key enzymes by ATP & AMP Catabolism Anabolism Fig ATP AMP ATP AMP starvation stimulates starvation inhibits

Acetyl-CoA Fig Fig Excess Glucose Stored in Form of Glycogen and Triacylglycerol