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Cellular Respiration

Cellular RespirationCellular Respiration: Harvesting Chemical Energy

Ppt from: aurumscience.comLife Requires EnergyLiving cells require energy from outside sourcesSome animals, such as the giant panda, obtain energy by eating plants; others feed on organisms that eat plants

Energy flows into an ecosystem as sunlight and leaves as heatPhotosynthesis uses sunlight to generate oxygen and glucose sugar.Cell respiration uses chemical energy in the form of carbohydrates, lipids, or proteins, to produce ATP.ATPATP stands for Adenosine Tri-PhosphateATP is a molecule that serves as the most basic unit of energyATP is used by cells to perform their daily tasks

ATPATP can be broken down into a molecule of ADP by removing one of the phosphate groups.This releases energy.ADP can be remade into ATP later when the cell has food that can be broken down (i.e. glucose)

NADHNADH is a molecule that can carry H+ ions and electrons from one part of the cell to another.NADH is the energized version of this molecule that is carrying the H+ ion and two high-energy electrons.NAD+ is the non-energized version of this molecule that does not have the ion or the extra two electrons.

LE 8-9Adenosine triphosphate (ATP)EnergyPPPPPPiAdenosine diphosphate (ADP)Inorganic phosphateH2O++

LE 9-2ECOSYSTEMLightenergyPhotosynthesisin chloroplastsCellular respirationin mitochondriaSimple sugars (Glucose)+ O2CO2 + H2OATPpowers most cellular workHeatenergyCell Respiration and Production of ATPThe breakdown of organic molecules (carbohydrates, lipids, proteins) releases energy.Cellular respiration consumes oxygen and organic molecules and yields ATPAlthough carbohydrates, fats, and proteins are all consumed as fuel, it is helpful to trace cellular respiration with the sugar glucose: C6H12O6 + 6O2 6CO2 + 6H2O + EnergyGlycolysisGlycolysis is the first stage of cellular respiration. Occurs in cytoplasm.During glycolysis, glucose is broken down into 2 molecules of the 3-carbon molecule pyruvic acid. ATP and NADH are produced as part of the process.

ATP Production2 ATP molecules are needed to get glycolysis started.

ATP ProductionGlycolysis then produces 4 ATP molecules, giving the cell a net gain of +2 ATP molecules for each molecule of glucose that enters glycolysis.

NADH ProductionDuring glycolysis, the electron carrier 2 NAD+ become 2 NADH.2 NADH molecules are produced for every molecule of glucose that enters glycolysis.

GlycolysisGlycolysis uses up:1 molecule of glucose (6-carbon sugar)2 molecules of ATP2 molecules of NAD+

Glycolysis produces2 molecules of pyruvic acid (3-carbon acids)4 molecules of ATP2 molecules of NADH

Advantages of GlycolysisGlycolysis produces ATP very fast, which is an advantage when the energy demands of the cell suddenly increase.

Glycolysis does not require oxygen, so it can quickly supply energy to cells when oxygen is unavailable.Movement to the Citric Acid CycleBefore the next stage can begin, pyruvic acid must first be transported inside the mitochondria.Pyruvic acid is combined with an enzyme called Coenzyme A. This enzyme helps with the transportation.Pyruvic acid + Coenzyme A make Acetyl CoAOne more molecule of NADH is produced.This also releases one molecule of CO2 as a waste product.

LE 9-10CYTOSOLPyruvateNAD+MITOCHONDRIONTransport proteinNADH+ H+Coenzyme ACO2Acetyl Co AKrebs CycleDuring the citric acid cycle, pyruvic acid produced in glycolysis is broken down into carbon dioxide and more energy is extracted.

Citric Acid CycleAcetyl-CoA from glycolysis enters the matrix, the innermost compartment of the mitochondrion.Once inside, the Coenzyme A is released.

Citric Acid CycleThe molecule of acetate that entered from glycolysis joins up with another 4-carbon molecule already present. This forms citric acid.

Citric Acid CycleCitric acid (6-carbon molecule) is broken down one step at a time until it is a 4-carbon molecule.The two extra carbons are released as carbon dioxide.

Citric Acid CycleEnergy released by the breaking and rearranging of carbon bonds is captured in the forms of ATP, NADH, and FADH2.FADH2 has the same purpose as NADH to transport high-energy electrons and H+ ions.

Citric Acid CycleFor each turn of the cycle, the following are generated:1 ATP molecule3 NADH molecules1 FADH2 molecule

Citric Acid CycleRemember! Each molecule of glucose results in 2 molecules of pyruvic acid, which enter the Krebs cycle.So each molecule of glucose results in two complete turns of the Krebs cycle.Therefore, for each glucose molecule:6 CO2 molecules,2 ATP molecules,8 NADH molecules,2 FADH2 molecules are produced.

LE 9-11Pyruvic acid(from glycolysis,2 molecules per glucose)ATPATPATPGlycolysisOxidationphosphorylationCitricacidcycleNAD+NADH+ H+CO2CoAAcetyl CoACoACoACitricacidcycleCO223 NAD++ 3 H+NADH3ATPADP + PiFADH2FADElectron Transport ChainThe electron transport chain occurs in the inner membrane of the mitochondria.Electrons are passed along the chain, from one protein to another.Each time the electron is passed, a little bit of energy is extracted from it.Electrons drop in energy as they go down the chain and until they end with O2, forming waterElectron Transport ChainNADH and FADH2 pass their high-energy electrons to electron carrier proteins in the electron transport chain.

Electron Transport ChainAt the end of the electron transport chain, the electrons combine with H+ ions and oxygen to form water.

Electron Transport ChainEnergy generated by the electron transport chain is used to move H+ ions (from NADH and FADH2) against a concentration gradient.This creates a dam of H+ ions in the outer fluid of the mitochondria.

The electron transport chain generates no ATPThe chains function is to break the large free-energy drop from food to O2 into smaller steps that release energy in manageable amounts.The end result is a reservoir of H+ ions that can be tapped for energy, much like a reservoir in a hydroelectric dam.

ChemiosmosisThe electron transport chain has created a high concentration of H+ ions in the outer fluid of the mitochondria.H+ then moves back across the membrane, into the inner fluid. H+ ions pass through a channel protein called ATP SynthaseATP synthase uses this flow of H+ to convert ADP molecules (low energy) into ATP (high energy)

LE 9-14INTERMEMBRANE SPACEH+H+H+H+H+H+H+H+ATPMITOCHONDRAL MATRIXADP+PiA rotor within the membrane spins as shown when H+ flows past it down the H+ gradient.A stator anchored in the membrane holds the knob stationary.A rod (or stalk) extending into the knob also spins, activating catalytic sites in the knob.Three catalytic sites in the stationary knob join inorganic phosphate to ADP to make ATP.Total ATP ProductionDuring cellular respiration, most energy flows in this sequence: glucose NADH electron transport chain chemiosmosis ATPAbout 40% of the energy in a glucose molecule is transferred to ATP during cellular respiration, making about 38 total ATPRemainder is lost as waste heat

FermentationCellular respiration requires O2 to produce ATPGlycolysis can produce ATP with or without O2 (in aerobic or anaerobic conditions)In the absence of O2, glycolysis can couples with a process called fermentation to produce ATP.Types of FermentationFermentation consists of glycolysis + reactions that regenerate NAD+, which can be reused by glycolysisTwo common types are alcohol fermentation and lactic acid fermentation

Alcohol FermentationYeast and a few other microorganisms use alcoholic fermentation that produces ethyl alcohol and carbon dioxide.This process is used to produce alcoholic beverages and causes bread dough to rise.Pyruvic acid + NADH Alcohol + CO2 + NAD+Lactic Acid FermentationMost organisms, including humans, carry out fermentation using a chemical reaction that converts pyruvic acid to lactic acid.Pyruvic acid + NADH Lactic acid + NAD+

In lactic acid fermentation, pyruvate is reduced to NADH, the only end product is lactic acid. No carbon dioxide is released.Lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurtHuman muscle cells use lactic acid fermentation to generate ATP when O2 is scarce (out of breath)Result: Soreness!

Yeast and many bacteria are facultative anaerobes, meaning that they can survive using either fermentation or cellular respirationMost other organisms cannot survive in the long-run using glycolysis and fermentation, they require oxygen. These are obligate aerobic organisms.

LE 9-18PyruvateGlucoseCYTOSOLNo O2 presentFermentationEthanolorlactateAcetyl CoAMITOCHONDRIONO2 present Cellular respirationCitricacidcycleThe Evolutionary Significance of GlycolysisGlycolysis occurs in nearly all organismsGlycolysis probably evolved in ancient prokaryotes before there was oxygen in the atmosphereOther Energy SourcesCatabolic pathways funnel electrons from many kinds of organic molecules into cellular respirationGlycolysis accepts a wide range of carbohydratesProteins must be digested to amino acids; amino groups can feed glycolysis or the citric acid cycleFats are digested to glycerol (used in glycolysis) and fatty acids (used in generating acetyl CoA) An oxidized gram of fat produces more than twice as much ATP as an oxidized gram of carbohydrate

LE 9-19CitricacidcycleOxidativephosphorylationProteinsNH3AminoacidsSugarsCarbohydratesGlycolysisGlucoseGlyceraldehyde-3-PPyruvateAcetyl CoAFattyacidsGlycerolFatsVideo Review on ATP & Respirationhttps://www.youtube.com/watch?v=00jbG_cfGuQ&list=PL3EED4C1D684D3ADF&index=7&feature=plpp_video