Biology Seventh Edition Solomon Berg Martin Chapter 7

Biology, Seventh Edition CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways • Cellular respiration • Aerobic respiration – Requires molecular oxygen – Includes redox reactions • Anaerobic – Anaerobic respiration – Fermentation – Do not require oxygen • All exergonic (releases energy… spontaneous…downhill reaction) Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways What Type of Process is Cellular Respiration? • An Oxidation-Reduction Process or REDOX Reaction • Oxidation of GLUCOSE --> CO 2 + H 2 O (e- removed from C 6 H 12 O 6) • Reduction O 2 to H 2 O (e- passed to O 2) Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways What Carries the Electrons? • NAD+ • • (nicotinadenine dinucleotide) acts as the energy carrier NAD+ is a coenzyme It’s Reduced to NADH when it picks up two electrons and one hydrogen ion Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways Are There Any Other Electron Carriers? • YES! Another Coenzyme! • FAD+ (Flavin adenine dinucleotide) • Reduced to FADH 2 Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways Other Cellular Respiration Facts • Metabolic Pathway that breaks down carbohydrates • Process is Exergonic as Highenergy Glucose is broken into CO 2 and H 2 O • Process is also Catabolic because larger Glucose breaks into smaller molecules Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways Review of Mitochondria Structure • Smooth outer Membrane • Folded inner membrane • Folds called Cristae • Space inside cristae called the Matrix Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways What are the Stages of Cellular Respiration? • Glycolysis • Formation of acetyl Co-A • • The Krebs Cycle The Electron Transport Chain Copyright Cmassengale Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways • Four stages of aerobic respiration • Takes place in the cytosol – Glycolysis • Takes place in the mitochondrion – Formation of acetyl Co. A – Citric acid cycle – Electron transport chain/chemiosmosis Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways Summary of aerobic

Biology, Seventh Edition CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways • Glycolysis • • “Sugar splitting” Occurs in the cytosol Does not require oxygen (anaerobic) Divided into two major phases – Energy investment phase – Energy capture phase • 1 glucose molecule produces net yield of two NADH molecules and two ATP molecules Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways Glycolysis Energy investment • Phosphorylation occurs 2 ATP molecules transfer a phosphate to a G 3 P sugar Energy Capture • 4 ATP molecules and 2 NADH Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways • Formation of acetyl Co. A • Catalyzed by enzyme pyruvate dehydrogenase – First carboxyl group is split off as carbon dioxide – Then remaining two-carbon fragment is oxidized and electrons transferred to NAD+ – Finally, oxidized two-carbon group is attached to coenzyme A Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways Formation of acetyl Co. A • Catalyzed by the multienzyme complex pyruvate dehydrogenase Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways • Citric acid cycle (Krebs Cycle) • For 1 glucose, two acetyl groups enter the citric acid cycle • Each two-carbon acetyl group combines with a four-carbon compound • Two CO 2 molecules are removed • Energy captured as one ATP, three NADH, and one FADH 2 per acetyl group (These will act as energy carriers for the electron transport chain) **So… 2 acetyl groups yields 4 CO 2, 6 NADH, 2 FADH 2, 2 ATP Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways Citric acid cycle • Also known as the Krebs Cycle or the tricarboxylic acid (TCA) cycle • Because 1 glucose produces 2 acetyl Co. A molecules two cycles are required per glucose • After 2 turns the original glucose can be said to have been completely consumed • **So… 2 acetyl groups yields 4 CO 2, 6 NADH, 2 FADH 2, 2 ATP Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways Detail of citric

Biology, Seventh Edition CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways A Little Krebs Cycle History • Discovered by Hans Krebs in 1937 • He received the Nobel Prize in physiology or medicine in 1953 for his discovery • Forced to leave Germany prior to WWII because he was Jewish Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways • Electron transport chain • Series of electron carriers • Each carrier exists in oxidized or reduced form • Electrons pass down the electron transport chain in series of redox reactions • Lose energy as pass along the chain • Released energy is used to pump protons across the inner membrane space (Hydrogen ions=protons) • Oxygen is the final electron acceptor Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways Electron Transport Chain Summary • 34 ATP Produced • Oxygen is the final electron acceptor • H 2 O Produced • Occurs Across Inner Mitochondrial membrane • Uses coenzymes NAD+ and FAD+ to accept e- from glucose • NADH = 3 ATP’s • FADH 2 = 2 ATP’s Copyright Cmassengale Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways Accumulation of protons

Biology, Seventh Edition CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways Electron transport and chemiosmosis Energy from the energy carriers is used to move the H+ ions Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways Energy yield from

Biology, Seventh Edition CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways What if Oxygen is not Available • Anaerobic respiration takes place • Not as efficient as aerobic respiration Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways Fermentation v Occurs when O 2 NOT present (anaerobic) v. Called Lactic Acid fermentation in muscle cells (makes muscles tired) v. Temporary and 80% of the lactate will be exported to liver and regenerated into more glucose for muscle cells v. Called Alcohol fermentation in yeast (produces ethanol) v. Basis for production of beer, wine, and makes bread dough rise v. Nets only 2 ATP Copyright Cmassengale Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways • Many organisms depend on nutrients other than glucose • Products of protein and lipid catabolism enter same metabolic pathways as glucose • Amino acids are deaminated Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways Energy from carbohydrates, proteins, and fats • Amino acids can have an amine group removed by demamination and converted to urea…leaving the carbon chain to be metabolized • Lipids will generate 44 ATP Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 7 How Cells Make ATP: Energy-Releasing Pathways • Anaerobic respiration versus fermentation • Anaerobic respiration – Electrons transferred from fuel molecules to electron transport chain – Final electron acceptor is inorganic substance • Fermentation – Anaerobic process that does not use electron transport chain Copyright © 2005 Brooks/Cole — Thomson Learning