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Chapter 9: CELLULAR RESPIRATION!!! Mr. Freidhoff Metabolism • Metabolism: The set of chemical reactions that occur in living organisms in order to maintain life. –Anabolism: Building up –Catabolism: Breaking down Cellular Respiration • Inputs: –Glucose –Oxygen • Outputs: –Carbon dioxide –Water –Energy (ATP) Cellular Respiration Equation C6H12O6 + 6O2 6CO2 + 6H2O + 38 ATP Reactions • Photosynthesis and Cellular Respiration are opposite reactions. Chemical Energy • Form of potential energy. • Chemical energy stored in Carbohydrates is transferred to ATP molecules. • Energy also released by heat. ATP Cycle • ATP is recyclable. • ADP and Phosphate group can be restored to ATP. – Input of energy – Where? • Foods • ATP is “energy currency.” • 10 million ATP can be regenerated in 1 minute. Aerobic vs. Anaerobic • Aerobic Process: Requires Oxygen. – If no oxygen is present, reaction will NOT occur. • Anaerobic Process: Doesn’t require oxygen. Cellular Respiration • Includes both aerobic and anaerobic respiration but is often used to refer to aerobic respiration. NAD/NADH • Each NADH represents stored energy. • NADH passes the electrons to the electron transport chain (ETC). • NAD+ + H → NADH • NAD+ are recyclable. FAD/FADH2 • Different chemical formula than NAD+. • Each FADH2 represents stored energy. – Also transport electrons to ETC. • FAD + H2 → FADH2 • FAD are recyclable. Cellular Respiration 3 Steps 1.Glycolysis 2.Krebs Cycle 3.Electron Transport Chain Glycolysis • Glyco = sugar; lysis = breaking. • Occurs in Cytoplasm. • 1 glucose molecule gets broken down into 2 (three carbon) pyruvates. – 2 ATP are used to break down glucose. Glycolysis • Produces 4 ATP, net of 2 ATP. • Produces 2 NADH. Glycolysis • Inputs: – Glucose • Outputs: – 2 NADH – Net of 2 ATP. – 2 pyruvate molecules. Oxidative decarboxylation • AKA: The transition step. • Small step between Glycolysis and Krebs Cycle. – Occurs in mitochondria matrix. • Converts Pyruvate (3C) to Acetyl CoA (2C). • Requires oxygen to occur. • Occurs twice. – Why? The Transition Step • Inputs: – 2 pyruvate molecules (3C) • Outputs: – 2 Acetyl CoA (2C) *When you lose a carbon, it’s always in the form of CO2 – 2 CO2 – 2 NADH Krebs Cycle • Also known as TCA or Citric Acid Cycle. • Discovered By Hans Krebs. • Cycle occurs twice for every glucose molecule. – Why? – You receive 2 Acetyl CoAs from Transition step. Krebs Cycle Krebs Cycle • Inputs: –2 Acetyl CoA • Outputs: –6 NADH –2 FADH2 –4 CO2 –2 ATP • Occurs in the mitochondrial matrix. • Several enzymes change compounds in the cycle. Electron Transport Chain • Located at the Inner Mitochondrial Membrane. • Inputs: 10 NADH and 2 FADH2. • Where are the NADH and FADH2 molecules coming from? – Glycolysis and Krebs Cycle. • Membrane proteins are binding sites for NADH and FADH2. Electron Transport Chain • NADH and FADH2 molecules donate their hydrogen ions and electrons at protein sites. • Electrons travel through ETC. • Hydrogen ions and electrons bond with oxygen to form water. – 6 H2O (Byproduct) ATP SYNTHASE!!! • Located in the membrane of mitochondria. • Bonds ADP and a phosphate group to make ATP. • Powered by Hydrogen ions. NADH and FADH2 • For every NADH molecule, 3 ATP are created. – 10 NADH x 3 ATP = 30 ATP • For every FADH2 molecule, 2 ATP are created. – 2 FADH2 x 2 ATP = 4 ATP • Total of 34 ATP created at the ETC. – Most out of three steps. Electron Transport Hydrogen Ion Movement Channel Intermembrane Space ATP synthase Inner Membrane Matrix ATP Production Energy Yield from Glucose Metabolism Electrons carried via NADH and FADH2 Electrons carried via NADH Citric acid cycle Glycolysis Pyruvate Glucose Oxidative phosphorylation: electron transport and chemiosmosis Mitochondrion Cytosol ATP ATP ATP Substrate-level phosphorylation Substrate-level phosphorylation Oxidative phosphorylation Mitochondria • Inner membrane is folded. – Called Cristae • What does this folding give the mitochondria? – More surface area. • Why is that important? – More and faster ATP production. – Evolutionary beneficial. Mitochondria • Found in plants and animals. • DNA found in mitochondrial matrix, not nucleus. • Mitochondrial DNA is passed down from mother to offspring. Mitochondria • Mitochondria started out as single celled prokaryotic cells. • Billions of years ago, eukaryotic life engulfed mitochondria and kept them around. • Why was this an evolutionary advantage? – Tons more ATP! Anaerobic Respiration • Not an efficient method of ATP production. • AKA: fermentation. • Two primary types: – Lactic Acid Fermentation – Alcohol Fermentation Lactic Acid Fermentation • In muscle tissues during rapid and vigorous exercise, muscle cells may be depleted of oxygen. • Muscles then switch from respiration to lacticacid fermentation. Lactic Acid Fermentation • Glycolysis is the only stage that occurs. • Glucose Pyruvate Lactic acid + energy • Notice that glycolysis doesn’t use Oxygen! Alcohol Fermentation • Occurs within some yeasts and bacteria. • Creates products such as wines and beers. • Fermentation also creates bread. Yeasts • Single celled fungi. • Go through fermentation by breaking down sugars and producing CO2. • Just one gram holds about 25 billion cells. Why is fermentation important to evolution? • 3.5 billion years ago, there was no oxygen on Earth. • Organisms evolved around the atmosphere at that time. How efficient is cell respiration? Energy released from glucose (as heat and light) Energy released from glucose banked in ATP Gasoline energy converted to movement About 40% 25% 100% Burning glucose in an experiment “Burning” glucose in cellular respiration Burning gasoline in an auto engine ATP Production • Aerobic Respiration: With Oxygen • Steps – Glycolysis: 2 ATP – Krebs Cycle: 2 ATP – Electron Transport Chain: 34 ATP • Total ATP: 38 ATP • Products: CO2, H20 • Anaerobic Respiration: Without Oxygen • Steps – Glycolysis: 2 ATP • Total ATP Production: 2 ATP • Products: Lactic Acid How Is a Marathoner Different from a Sprinter? • Individuals inherit various percentages of the two main types of muscle fibers, slow and fast. – The difference between the two is the process each uses to make ATP. – Slow fibers make it aerobically using oxygen. – Fast fibers work anaerobically without oxygen. How Is a Marathoner Different from a Sprinter? • The percentage of slow and fast muscle fibers determines the difference between track athletes. – Those with a large percentage of slow fibers make the best long-distance runners. – Those with more fast fibers are good sprinters.