Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig Draw this drawing on a blank sheet of cellulose.

Chapter 6 How Cells Harvest Chemical Energy Introduction to Cell Metabolism Glycolysis Aerobic Cell Respiration Anaerobic Cell Respiration

O2O2 CO 2 BREATHING Lungs CO 2 O2O2 Bloodstream Muscle cells carrying out CELLULAR RESPIRATION Sugar + O 2  ATP + CO 2 + H 2 O Breathing and Cell Respiration are related

GlucoseOxygen gasCarbon dioxide WaterEnergy Cellular Respiration uses oxygen and glucose to produce Carbon dioxide, water, and ATP.

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

Loss of hydrogen atoms Glucose Gain of hydrogen atoms Energy Reduction and Oxidation OILRIG Oxidation is losing electrons Reduction is gaining electrons Glucose gives off energy as is 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? NAD+ and FAD NAD+ + 2 H  NADH + H+ FAD + 2 H  FADH 2 Remember that H = 2 electrons and 2H+

Reduction and Oxidation These co-enzymes are very important for cell respiration because they transfer high-energy electrons to electron transport systems (ETS).

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

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

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.

Generation of ATP Chemiosmosis

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

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

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

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

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

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

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

Each pyruvic acid molecule is broken down to form CO 2 and a two-carbon acetyl group, which enters the Krebs cycle Acetyl CoA Pyruvic Acid

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

Krebs Cycle Where? In the Mitochondria What? Uses Acetyl Co-A to generate ATP, NADH, FADH 2, and CO 2.

Krebs Cycle

General Outline of Aerobic Respiration Glycolysis Krebs Cycle Electron Transport System

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

Electron Transport System

For each glucose molecule that enters cellular respiration, chemiosmosis produces up to 38 ATP molecules

Overview of Aerobic Respiration

General Outline Glucose Pyruvic Acid Glycolysis Oxygen Aerobic No Oxygen Anaerobic Transition Reaction Krebs Cycle ETS 36 ATP 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 few ATP are produced per glucose

Fermentation