Presentation on theme: "Inquiry into Life Eleventh Edition Sylvia S. Mader"— Presentation transcript:
1 Inquiry into Life Eleventh Edition Sylvia S. Mader Chapter 7Lecture OutlineCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
2 7.1 Overview of cellular respiration Overall processOxidation of glucose to carbon dioxide, water, and energy. This is an Exergonic reaction used to drive ATP synthesis which is endergonic4 phases of respiration are required for complete oxidation of glucoseOxidation involves the removal of hydrogen atoms from substrates by redox coenzymes NAD+ and FAD
6 Overview of cellular respiration cont’d. Phases of cellular respirationGlycolysis (Takes place in the Cytoplasm)Use Energy from 2 ATP’s to activate glucoseBreakdown of glucose to 2 molecules of pyruvateOxidation by removal of hydrogens releases enough energy to make 2 ATP’s from each pyruvate results in a Net Gain of 2 ATP’s in this Phase per Glucose Molecule.
7 Phases of cellular respiration, cont’d. Preparatory reaction (Takes place in Matrix of Mitochondria)Pyruvate oxidized to acetyl CoA and carbon dioxide is removedPrep reaction occurs twice per Glucose molecule because glycolysis produces 2 pyruvatesNo ATP’s produced in this phase
8 Phases of cellular respiration, cont’d. Citric acid cycle (Takes place in Matrix of Mitochondria)Each Pyruvate was oxidized to acetyl CoA in Preparatory Reaction.Now Acetyl CoA is converted to citric acid and enters the cycleCyclical series of oxidation reactions that produces 1 ATP and carbon dioxide per cycle turnCitric acid cycle turns twice per Glucose Molecule because 2 acetyl CoA’s are produced per glucose2 ATP’s produced per Glucose Molecule in this phase
9 Overview of cellular respiration cont’d. Phases of cellular respiration, cont’d.Electron transport chain (Takes place in Cristae of Mitochondria)Series of electron carrier molecules which pass Electrons from one carrier to another releasing energy to make ATPAs the electrons move from a higher energy state to a lower one, energy is released to make ATPUnder aerobic conditions ATP per glucose molecule can be produced
10 Phases of cellular respiration, cont’d. In Anaerobic Conditions (No Oxygen Present)Glycolysis produces PyruvatePivotal metabolite in cellular respirationIf no oxygen is available, pyruvate is reduced to lactate (in animals) or ethanol and carbon dioxide (in plants) in a process called fermentation
12 7.2 Outside the mitochondria: Glycolysis Energy-investment stepsEnergy from 2 ATP is used to activate glucoseGlucose is split into 2 3-carbon G3P moleculesEnergy-harvesting stepsOxidation of G3P by removal of hydrogensHydrogens are picked up by NAD+ to form NADHOxidation of G3P and further substrates yields enough energy to produce 4 ATP by direct substrate phosphorylation, so there’s a net gain of 2 ATP’s.
13 Outside the mitochondria: glycolysis cont’d. Glycolysis yields:4 ATP by direct substrate phosphorylation2 ATP were consumed in the investments stepsNet gain of ATP from glycolysis is therefore 2 ATP2 NADH which will carry electrons to the electron transport chainNo Oxygen is required for Glycolysis to produce pyruvate.When oxygen is available pyruvate will enter the mitochondria for further oxidationIf no oxygen is available, pyruvate will enter the fermentation pathway
15 7.3 Inside the mitochondria Breathing, eating, and cellular respirationOxygen is taken in by breathingDigested food contains glucoseOxygen and glucose are carried to cells by the bloodstreamGlucose and oxygen enter cells where respiration occursCarbon dioxide is taken by the bloodstream to the lungs
16 Relationship between breathing, eating, and cell respiration
17 Inside the mitochondria cont’d. Preparatory reactionProduces the molecule that will enter the citric acid cycle3C pyruvate is converted to 2C acetyl CoACarbon dioxide is producedHydrogen atoms are removed from pyruvate and picked up to form NADHThis reaction occurs twice per glucose
18 Inside the mitochondria cont’d. Citric acid cycle2C acetyl group from prep reaction combines with a 4C molecule to produce 6C citrateOxidation of citrate by removal of hydrogensProduces 3 NADH and 1 FADH2Produces 1 ATP per cycle by direct substrate phosphorylationCycle turns twice per glucoseTotal yield: 6 NADH, 2 FADH2, 2 ATP, 4 CO2
20 Inside the mitochondria cont’d. Electron transport chain (ETC)2 electrons per NADH and FADH2 enter ETCElectrons are passed to series of electron carriers called cytochromesEnergy is captured and stored as a hydrogen ion concentration gradient. This process is called chemiosmosisFor each NADH enough energy is released to form 3 ATPFor each FADH2 there are 2 ATP produced
22 Inside the mitochondria cont’d. Electron transport chain cont’d.the final electron acceptor is oxygenAfter receiving electrons oxygen combines with hydrogen ions to form water as an end product ½ O2+ 2 e- + 2H+ H2ONAD+ and FAD recycle back to pick up more electrons from glycolysis, prep reaction, and citric acid cycle
23 Inside the mitochondria cont’d. Organization of cristaeElectron carriers are arranged along the cristaeAs electrons are passed, energy is used to pump H+ into the intermembrane space of mitochondrionThis builds an electro-chemical gradient that stores energyAs H+ moves back into matrix energy is released and captured to form ATP by ATP synthase complexesProcess is called chemiosmosis
25 Inside the mitochondria cont’d. Energy yield from cellular respiration is 36 – 38 ATP’s per Glucose MoleculeFrom direct phosphorylationNet of 2 ATP from glycolysis2 ATP from citric acid cycleFrom chemiosmosisElectron transport chain produces 32 – 34 ATP per Glucose Molecule
26 Accounting of energy yield per glucose molecule breakdown
27 Inside the mitochondria cont’d. Efficiency of cellular respirationThe difference in energy content of reactants (glucose and oxygen) and products (carbon dioxide and water) is 686 kcalATP phosphate bond has 7.3 kcal of energy36 ATP are produced in respiration 36 X 7.3 = 263 kcal263/686 = 39% efficiency of energy captureThe rest of the energy is lost as heat
28 7.4 Fermentation Fermentation Produces only a net of 2 ATP per glucose Occurs when O2 is not availableAnimal cells convert pyruvate to lactatePlant cells, yeasts convert pyruvate to ethanol and CO2Fermentation regenerates NAD+ which keeps glycolysis goingProduces only a net of 2 ATP per glucose
30 Fermentation cont’d. Advantages and Disadvantages of fermentation Provides a low but continuous supply of ATP when oxygen is limited and only glycolysis can functionCan provide a rapid burst of ATP in muscle cells, even when oxygen is in limited supply.Lactate is potentially toxic to muscles, lowering pH and causing fatigueTransported to liver where it is converted to pyruvateThis process requires oxygenDuring exercise an oxygen debt is built upOxygen debt is the amount of oxygen “owed” to the liver to convert accumulated lactic acid to pyruvate
31 Fermentation , cont’d. Energy yield of fermentation Produces only a net of 2 ATP per glucose through direct substrate phosphorylation by allowing glycolysis to continue. MUCH LESS efficient than Aerobic Cellular Respiration.Following fermentation most of the potential energy from glucose is still waiting to be releasedFermentation is a way to continue an ATP supply to cells when oxygen is in short supply
32 7.5 Metabolism Catabolism-break down reactions Carbohydrates-digested to glucose for cell respirationFats-digested to glycerol and fatty acidsGlycerol can enter glycolytic pathwayFatty acids metabolized to acetyl CoA which enters citric acid cycleProteins- deaminationAmino acids can enter pathway at different points
34 Metabolism cont’d. Anabolism- synthesis reactions Substrates of glycolysis and citric acid cycle can be substrates for synthesis of macromoleculesG3P can be converted to glycerolAcetyl groups can be converted to fatty acidsSome citric acid intermediates can be converted to amino acidsAnabolic reactions require the input of energy in the form of ATP generated in catabolic reactions
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