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How Cells Harvest Chemical Energy How Cells Harvest Chemical Energy Global Athlete Outreach Program US CytoThesis Systems Medicine Center www.CytoThesis.US US OncoTherapy Systems BioMedicine Group CytoThesis Bioengineering Research Group General Biology – Dept Mathematics Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings How is a Marathoner Different from a Sprinter ? • Long-distance runners have many slow muscle fibers in their muscles – Slow muscle fibers break down glucose for ATP production aerobically using oxygen – These muscle cells can sustain repeated, long contractions Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Sprinters have more fast muscle fibers – Fast fibers make ATP without oxygen— anaerobically – They can contract quickly and supply energy for short bursts of intense activity Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • The dark meat of a cooked turkey is an example of slow fiber muscle – Leg muscles support sustained activity – The white meat consists of fast fibers (less myoglobin) – Wing muscles allow for quick bursts of flight dark meat white meat Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings INTRODUCTION TO CELLULAR RESPIRATION • Nearly all the cells in our body break down sugars for ATP production • Most cells of most organisms harvest energy aerobically, like slow muscle fibers – The aerobic harvesting of energy from sugar is called cellular respiration – Cellular respiration yields CO2, H2O, and a large amount of ATP Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 6.1 Breathing supplies oxygen to our cells and removes carbon dioxide • Breathing and cellular respiration are closely related BREATHING O2 CO2 Lungs CO2 Bloodstream O2 Muscle cells carrying out CELLULAR RESPIRATION Sugar + O2 ATP + CO2 + H2O Figure 6.1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 6.2 Cellular respiration banks energy in ATP molecules • Cellular respiration breaks down glucose molecules and banks their energy in ATP – The process uses O2 and releases CO2 and H2O Glucose Oxygen gas Carbon Water Energy dioxide Figure 6.2A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • The efficiency of cellular respiration (and comparison with an auto engine) Energy released Energy released Gasoline energy from glucose from glucose converted to (as heat and light) banked in ATP movement 100% heat About 40% 25% Burning glucose “Burning” glucose Burning gasoline in an experiment in cellular respiration in an auto engine Figure 6.2B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 6.3 Connection: The human body uses energy from ATP for all its activities • ATP powers almost all cell and body activities Table 6.3 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings BASIC MECHANISMS OF ENERGY RELEASE AND STORAGE 6.4 Cells tap energy from electrons transferred from organic fuels to oxygen • Glucose gives up energy as it is oxidized Loss of hydrogen atoms Energy Glucose Gain of hydrogen atoms Figure 6.4 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 6.5 Hydrogen carriers such as NAD+ shuttle electrons in redox reactions • The movement of electrons from one molecule to another is an oxidation-reduction reaction, or redox reaction • In a redox reaction, the loss of electrons from one substance is called oxidation, and the addition of electrons to another substance is called reduction • Enzymes remove electrons from glucose molecules and transfer them to a coenzyme Figure 6.5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings loss of electrons OXIDATION Dehydrogenase and NAD+ NAD+: nicotinamide adenine dinucleotide REDUCTION addition of electrons Figure 6.5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 6.6 Redox reactions release energy when electrons “fall” from a hydrogen carrier to oxygen • NADH delivers electrons to a series of electron carriers in an electron transport chain – As electrons move from carrier to carrier,Each carrier their ehas- than a greater its uphill energy is released in small quantitiesaffinity for neighbor. Energy released and now available for making ATP Electron flow ELECTRON CARRIERS of the electron transport chain Figure 6.6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • In an explosion, 02 is reduced in one step. • All the energy is released as heat and light. Energy released as heat and light Figure 6.6B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 6.7 Two mechanisms generate ATP High H+ concentration • Cells use the energy ATP synthase uses gradient released by “falling” energy to make ATP electrons to pump H+ Membrane ions across a membrane Electron transport – The energy of the chain gradient is harnessed ATP to make ATP by the synthase process of chemiosmosis Energy from Low H+ concentration Figure 6.7A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • ATP can also be made by transferring Enzyme phosphate groups from organic molecules to ADP Adenosine Organic molecule (substrate) – This process is called Adenosine substrate-level phosphorylation New organic molecule (product) Figure 6.7B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings STAGES OF CELLULAR RESPIRATION AND FERMENTATION 6.8 Overview: Respiration occurs in three main stages • Cellular respiration oxidizes sugar and produces ATP in three main stages – Glycolysis occurs in the cytoplasm – The Krebs cycle and the electron transport chain occur in the mitochondria Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • An overview of cellular respiration High-energy electrons carried by NADH GLYCOLYSIS KREBS ELECTRON TRANSPORT CHAIN Glucose Pyruvic CYCLE acid AND CHEMIOSMOSIS Cytoplasmic fluid Mitochondrion Figure 6.8 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 6.9 Glycolysis harvests chemical energy by oxidizing glucose to pyruvic acid Glucose Pyruvic acid Figure 6.9A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings PREPARATORY Steps 1 – 3 A fuel Glucose PHASE molecule is energized, Step (energy investment) • Details of using ATP. 1 Glucose-6-phosphate glycolysis 2 Fructose-6-phosphate 3 Fructose-1,6-diphosphate Step 4 A six-carbon 4 intermediate splits into two three-carbon Glyceraldehyde-3-phosphate intermediates. (G3P) 5 ENERGY PAYOFF Step 5 A redox PHASE reaction generates NADH. 1,3-Diphosphoglyceric acid (2 molecules) 6 Steps 6 – 9 ATP 3-Phosphoglyceric acid and pyruvic acid 7 (2 molecules) are produced. 2-Phosphoglyceric acid 8 (2 molecules) 2-Phosphoglyceric acid (2 molecules) 9 Pyruvic acid Figure 6.9B (2 molecules per glucose molecule) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 6.10 Pyruvic acid is chemically groomed for the Krebs cycle • Each pyruvic acid molecule is broken down to form CO2 and a two-carbon acetyl group, which enters the Krebs cycle Pyruvic Acetyl CoA acid (acetyl coenzyme A) CO2 Figure 6.10 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 6.11 The Krebs cycle completes the oxidation of organic fuel, generating many NADH and FADH2 molecules • The Krebs cycle is a Acetyl CoA series of reactions in which enzymes strip away electrons and + H from each acetyl KREBS 2 CO group CYCLE 2 FADH2 : flavin adenine dinucleotide -reduced FAD: flavin adenine dinucleotide -oxidized Figure 6.11A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 2 carbons enter cycle Oxaloacetic acid 1 Citric acid 5 CO2 leaves cycle KREBS 2 CYCLE Malic acid 4 Alpha-ketoglutaric acid 3 CO2 leaves cycle Succinic acid Step 1 Steps 2 and 3 Steps 4 and 5 Acetyl CoA stokes NADH, ATP, and CO2 are generated Redox reactions generate FADH2 the furnace during redox reactions. and NADH. Figure 6.11B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 6.12 Chemiosmosis powers most ATP production • The electrons from NADH and FADH2 travel down the electron transport chain to oxygen • Energy released by the electrons is used to pump H+ into the space between the mitochondrial membranes • In chemiosmosis, the H+ ions diffuse back through the inner membrane through ATP synthase complexes, which capture the energy to make ATP Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Chemiosmosis in the mitochondrion Protein complex Intermembrane Electron space carrier Inner mitochondrial membrane Electron flow Mitochondrial matrix ELECTRON TRANSPORT CHAIN ATP SYNTHASE Figure 6.12 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 6.13 Connection: Certain poisons interrupt critical events in cellular respiration cyanide ， rotenone oligomycin carbon monoxide ELECTRON TRANSPORT CHAIN ATP SYNTHASE Figure 6.13 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 6.14 Review: Each molecule of glucose yields many molecules of ATP • For each glucose molecule that enters cellular respiration, chemiosmosis produces up to 38 ATP molecules Cytoplasmic Mitochondrion fluid Electron shuttle across membranes KREBS GLYCOLYSIS 2 KREBS CYCLEELECTRON 2 Acetyl Glucose Pyruvic CYCLE TRANSPORT CHAIN CoA AND CHEMIOSMOSIS acid by substrate-level used for shuttling electrons by substrate-level by chemiosmotic phosphorylation from NADH made in glycolysis phosphorylation phosphorylation Maximum per glucose:
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