How Cells Harvest Chemical Energy Chapter 9 How Cells Harvest Chemical Energy Introduction to Cell Metabolism Glycolysis Aerobic Cell Respiration Anaerobic Cell Respiration

Breathing and Cell Respiration are related CO2 Lungs Muscle cells carrying out CO2 Bloodstream O2 CELLULAR RESPIRATION Sugar + O2  ATP + CO2 + H2O

How efficient is cell respiration? Energy released from glucose banked in ATP Energy released from glucose (as heat and light) Gasoline energy converted to movement 100% About 40% 25% Burning glucose in an experiment “Burning” glucose in cellular respiration Burning gasoline in an auto engine

Reduction and Oxidation OILRIG Oxidation is losing electrons Reduction is gaining electrons Loss of hydrogen atoms Energy Glucose Gain of hydrogen atoms Glucose gives off energy and is oxidized

Reduction and Oxidation OILRIG Gain or loss of electrons is often in the form of hydrogen. The hydrogen is then passed to a coenzyme such as NAD+

Reduction and Oxidation What are some common co-enzymes/electron carriers? NAD+ and FAD NAD+ + 2 H  NADH + H+ FAD + 2 H  FADH2

Generation of ATP There are two ways to generate ATP Chemiosmosis Substrate-Level Phosphorylation

Generation of ATP Substrate Level Phosphorylation Enzyme ATP can also be made by transferring phosphate groups from organic molecules to ADP Adenosine substrate Adenosine product Figure 6.7B

Generation of ATP Substrate Level Phosphorylation Enzyme ATP can also be made by transferring phosphate groups from organic molecules to ADP Adenosine substrate Adenosine product Figure 6.7B

Glycolysis General Outline No Oxygen Anaerobic Oxygen Aerobic Glucose Glycolysis No Oxygen Anaerobic Oxygen Aerobic Pyruvic Acid Transition Reaction Fermentation Krebs Cycle ETS 36 ATP

Glycolysis Where? The cytosol What? Breaks down glucose to pyruvic acid

Glycolysis Energy In: 2 ATP Energy Out: 4 ATP NET 2 ATP Steps – A fuel molecule is energized, using ATP. Glucose 1 3 Step Glycolysis 1 Glucose-6-phosphate 2 Fructose-6-phosphate Energy In: 2 ATP 3 Fructose-1,6-diphosphate Step A six-carbon intermediate splits into two three-carbon intermediates. 4 4 Glyceraldehyde-3-phosphate (G3P) (TRIOSE PHOSPHATE) 5 Step A redox reaction generates NADH. 5 1,3-Diphosphoglycerate (2 molecules) 6 Steps – ATP and pyruvic acid are produced. 3-Phosphoglycerate (2 molecules) Energy Out: 4 ATP 6 9 7 2-Phosphoglycerate(2 molecules) 8 2-Phosphoglycerate(2 molecules) NET 2 ATP 9 Pyruvic acid (2 molecules per glucose molecule)

General Outline of Aerobic Respiration Glycolysis Transition Reaction Krebs Cycle Electron Transport System

Transition Reaction/Pre-Krebs/Link Reaction: Occurs in the Matrix Each pyruvic acid molecule is broken down to form CO2 and a two-carbon acetyl group, which enters the Krebs cycle. An Oxidative Decarboxylation Reaction: Pyruvic Acid Acetyl CoA

General Outline of Aerobic Respiration Glycolysis Transition Reaction Krebs Cycle Electron Transport System

Krebs Cycle

Krebs Cycle

General Outline of Aerobic Respiration Glycolysis Krebs Cycle Electron Transport System

Electron Transport System

ELECTRON TRANSPORT CHAIN Electron Transport System Protein complex Intermembrane space Electron carrier Inner mitochondrial membrane Electron flow Mitochondrial matrix ELECTRON TRANSPORT CHAIN ATP SYNTHASE Figure 6.12

Generation of ATP Chemiosmosis Cells use the energy released by “falling” electrons in the ETS to pump H+ ions across a membrane Uses the enzyme ATP synthase.

Reduction and Oxidation As the electrons move from carrier to carrier, energy is released in small quantities. Electron transport system (ETS)

Generation of ATP Chemiosmosis

CHEMIOSMOSIS The coupling of ATP synthesis to electron transport via a concentration gradient. It is the MECHANISM for oxidative phosphorylation in Aerobic C.R. and Photosynthesis

Overview of Aerobic Respiration

Fermentation Requires NADH generated by glycolysis. Where do you suppose these reactions take place? Yeast produce carbon dioxide and ethanol Muscle cells produce lactic acid Only a 2 ATP are produced per glucose

Fermentation