Presentation on theme: "Harvesting stored energy"— Presentation transcript:
1 Harvesting stored energy Glucose is the modelcatabolism of glucose to produce ATPglucose + oxygen energy + water + carbondioxiderespiration+ heatC6H12O66O2ATP6H2O6CO2+fuel (carbohydrates)COMBUSTION = making a lot of heat energy by burning fuels in one stepMovement of hydrogen atoms from glucose to waterRESPIRATION = making ATP (& some heat) by burning fuels in many small stepsATPATPglucoseenzymesO2O2CO2 + H2O + heatCO2 + H2O + ATP (+ heat)
2 ATP = adenosine triphosphate -the energy “currency” of cellsATP stores energy in the bonds between phosphates
3 Energy Currency of Cells When the bond between phosphates is broken:ATP ADP + Pienergy is releasedADP = adenosine diphosphatePi = inorganic phosphateThis reaction is reversible.
4 ATP ADP + Pi Really high energy bond ATP – adenosine tri(3) phosphate. Energy is used to attach a third phosphate group onto ADP –adenosine di(2) phosphate. ATP is often called the energy currency of the cell. Its energy that can be saved and used later as needed. But like money it has to be earned.
5 How do we harvest energy from fuels? Digest large molecules into smaller onesbreak bonds & move electrons from one molecule to anotheras electrons move they “carry energy” with themthat energy is stored in another bond, released as heat or harvested to make ATP• They are called oxidation reactions because it reflects the fact that in biological systems oxygen, which attracts electrons strongly, is the most common electron acceptor.• Oxidation & reduction reactions always occur together therefore they are referred to as “redox reactions”.• As electrons move from one atom to another they move farther away from the nucleus of the atom and therefore are at a higher potential energy state.The reduced form of a molecule has a higher level of energy than the oxidized form of a molecule. • The ability to store energy in molecules by transferring electrons to them is called reducing power, and is a basic property of living systems.loses e-gains e-oxidizedreduced+–+e-e-e-oxidationreductionredox
6 How do we move electrons in biology? Moving electrons in living systemselectrons cannot move alone in cellselectrons move as part of H atommove H = move electronspe+H–loses e-gains e-oxidizedreducedoxidationreductionEnergy is transferred from one molecule to another via redox reactions.C6H12O6 has been oxidized fully == each of the carbons (C) has been cleaved off and all of the hydrogens (H) have been stripped off & transferred to oxygen (O) — the most electronegative atom in living systems. This converts O2 into H2O as it is reduced.The reduced form of a molecule has a higher energy state than the oxidized form. The ability of organisms to store energy in molecules by transferring electrons to them is referred to as reducing power. The reduced form of a molecule in a biological system is the molecule which has gained a H atom, hence NAD+ NADH once reduced.soon we will meet the electron carriers NAD & FADH = when they are reduced they now have energy stored in them that can be used to do work.C6H12O66O26CO26H2OATP+oxidationHreductione-
7 Moving electrons in respiration Electron carriers move electrons by shuttling H atoms aroundNAD+ NADH (reduced)FAD+2 FADH2 (reduced)reducing power!PO–O–OCNH2N+Hadenineribose sugarphosphatesNAD+nicotinamideVitamin B3niacinNADHPO–O–OCNH2N+HHHow efficient!Build once, use many ways+HreductionNicotinamide adenine dinucleotide (NAD) — and its relative nicotinamide adenine dinucleotide phosphate (NADP) which you will meet in photosynthesis — are two of the most important coenzymes in the cell.In cells, most oxidations are accomplished by the removal of hydrogen atoms. Both of these coenzymes play crucial roles in this.Nicotinamide is also known as Vitamin B3 is believed to cause improvements in energy production due to its role as a precursor of NAD (nicotinamide adenosine dinucleotide), an important molecule involved in energy metabolism. Increasing nicotinamide concentrations increase the available NAD molecules that can take part in energy metabolism, thus increasing the amount of energy available in the cell.Vitamin B3 can be found in various meats, peanuts, and sunflower seeds. Nicotinamide is the biologically active form of niacin (also known as nicotinic acid).FAD is built from riboflavin — also known as Vitamin B2. Riboflavin is a water-soluble vitamin that is found naturally in organ meats (liver, kidney, and heart) and certain plants such as almonds, mushrooms, whole grain, soybeans, and green leafy vegetables. FAD is a coenzyme critical for the metabolism of carbohydrates, fats, and proteins into energy.oxidationcarries electrons as a reduced molecule
8 Steps of RespirationThe complete oxidation of glucose proceeds in stages:1. glycolysis2. pyruvate oxidation3. Krebs cycle4. electron transport chain & chemiosmosis
10 Glycolysis 6C 3C Breaking down glucose glucose pyruvate 2x “glyco – lysis” (splitting sugar)ancient pathway which harvests energywhere energy transfer first evolvedtransfer energy from organic molecules to ATPstill is starting point for ALL cellular respirationbut it’s inefficientgenerate only 2 ATP for every 1 glucoseoccurs in cytosolglucose pyruvate2x6C3CWhy does it make sense that this happens in the cytosol?Who evolved first?That’s not enough ATP for me!
11 Mitochondria — Structure Double membrane energy harvesting organellesmooth outer membranehighly folded inner membranecristaeintermembrane spacefluid-filled space between membranesmatrixinner fluid-filled spaceDNA, ribosomesenzymesfree in matrix & membrane-boundintermembranespaceinnermembraneoutermatrixcristaemitochondrial DNAWhat cells would have a lot of mitochondria?
12 Mitochondria – Function Dividing mitochondriaWho else divides like that?Membrane-bound proteinsEnzymes & permeasesbacteria!Almost all eukaryotic cells have mitochondriathere may be 1 very large mitochondrion or 100s to 1000s of individual mitochondrianumber of mitochondria is correlated with aerobic metabolic activitymore activity = more energy needed = more mitochondriaWhat cells would have a lot of mitochondria?Active cells:• muscle cells• nerve cellsWhat does this tell us about the evolution of eukaryotes?Endosymbiosis!Advantage of highly folded inner membrane?More surface area for membrane-bound enzymes & permeases
13 [ ] Oxidation of pyruvate Pyruvate enters mitochondrial matrix 3 step oxidation processreleases 2 CO2 (count the carbons!)reduces 2 NAD 2 NADH (moves e-)produces 2 acetyl CoAAcetyl CoA enters Krebs cycle[2x]pyruvate acetyl CoA + CO23CNAD2C1CWhere does the CO2 go?Exhale!CO2 is fully oxidized carbon == can’t get any more energy out itCH4 is a fully reduced carbon == good fuel!!!
14 3. Krebs Cycle -oxidizes the acetyl Co-A -occurs in the matrix of the mitochondria
15 Krebs CycleAfter glycolysis, pyruvate oxidation, and the Krebs cycle, glucose has been oxidized to:- 6 CO2- 4 ATP- 10 NADH- 2 FADH2These electron carriers proceedto the electron transport chain.
16 Electron Transport Chain series of proteins built into inner mitochondrial membraneyields ~36 ATP from 1 glucose!only in presence of O2 (aerobic respiration)That sounds more like it!O2
17 Electron carriers pass electrons & H+ to ETC H cleaved off NADH & FADH2electrons stripped from H atoms H+ (protons)electrons passed from one electron carrier to next in mitochondrial membrane (ETC)flowing electrons = energy to do worktransport proteins in membrane pump H+ (protons) across inner membrane to intermembrane spaceNAD+QCNADHH2OH+e–2H+ +O2FADH212NADH dehydrogenasecytochrome bc complexcytochrome c oxidase complexFADOxidation refers to the loss of electrons to any electron acceptor, not just to oxygen.Uses exergonic flow of electrons through ETC to pump H+ across membrane.H+H+H+
18 Allow the protons to flow through ATP synthase “proton-motive” forceChemiosmosis:Set up a H+ gradientAllow the protons to flow through ATP synthaseSynthesizes ATPADP + Pi ATPH+ADP + PiATP
19 ATP Pyruvate from cytoplasm Intermembrane space Inner mitochondrial ElectrontransportsystemCQNADHe-2. Electrons provide energy to pump protons across the membrane.H+1. Electrons are harvested and carried to the transport system.e-Acetyl-CoANADHe-H2OKrebscyclee-3. Oxygen joins with protons to form water.1FADH2O22O2+2H+CO2H+ATPATPH+ATP4. Protons diffuse back in down their concentration gradient, driving the synthesis of ATP.ATPsynthaseMitochondrialmatrix
21 Oxidation Without O2 Respiration occurs without O2 via either: 1. anaerobic respiration-methanogens (CO2 CH4)-sulfur bacteria (SO4 H2S)2. fermentation-ethanol (yeast)-lactic acid (animal cells)
22 Pyruvate is a branching point fermentationanaerobic respirationmitochondriaKrebs cycleaerobic respiration
23 Fermentation (anaerobic) Bacteria, yeast1C3C2Cpyruvate ethanol + CO2NADHNAD+back to glycolysisbeer, wine, breadAnimals, some fungiCount the carbons!!Lactic acid is not a dead end like ethanol. Once you have O2 again, lactate is converted back to pyruvate by the liver and fed to the Kreb’s cycle.pyruvate lactic acid3CNADHNAD+back to glycolysischeese, anaerobic exercise (no O2)
24 Catabolism of Protein & Fat In the absence of carbohydrates, animals can break down other molecules:-proteins: amino acids converted to a molecule that enters glycolysis or the Krebs cycle-fats: fatty acids enter Krebs cycle (produces more energy than glucose)