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1 CELL RESPIRATION AND FERMENTATION Khan Academy 15min cell respiration Bozeman biology What is cellular respiration? Stepwise oxidation of high energy food molecules to low energy molecules: CO2 + H2O organic mol. + O2 ----- CO2 + H2O + Energy Fire is an oxidation rxn but unlike living systems it releases Energy all at once. Living systems respiration occurs in a series of controlled steps releasing food energy a little at a time. AEROBIC RESPIRATION: ( 38atp/glucose) W/ OXYGEN (CH2O)n + O2 --- CO2 + H2O + Energy ANAEROBIC RESPIRATION ( FERMENTATION) w/o oxygen ( 2atp/glucose ) Breakdown of food using organic mol. Instead of Oxygen as an oxidizer. ( much less efficient ) 2 -Fermentation ( anaerobic) : only breaks down food molecules(glucose) part way. -Energy stored as chemical potential energy -There are other metabolic pathways for proteins and lipids that feed molecules into the respiratory pathway. OVERVIEW OF THE BREAKDOWN OF GLUCOSE UNDER AEROBIC CONDITIONS: 1. Glucose ( C6H12O6) is broken down to Carbon dioxide and water in a long series of exergonic rxns. 2. Some of the energy stored in the glucose molecules chem. Bonds is used to make ATP. 3. Most of the energy transfer occurs as hydrogen atoms removed from glucose are passed through a pathway called the electron transport system in a series of redox rxns. 3 COENZYMES: (NAD+ , FAD+2) 1. Organic molecules that help to carry substances from one rxn to another. ( in this case: specifically hydrogen atoms) NADH , FADH2 2. Many coenzymes are made from vitamins 3. Coenzymes are reuseable: a.NAD nicotinamide adenine dinucleotide b. FAD flavin adenine dinucleotide OVERALL OXIDATION OF ONE GLUCOSE DURING CELL RESPIRATION: 4 BASIC PARTS: 1. Glycolysis 2. Preparation for the CAC ( citric acid cycle) ( also known as the kreb cycle) 3. Citric acid Cycle 4. e- transport and chemiosmotic ATP synthesis 4 1. GLYCOLYSIS: a. Breaks down GLUCOSE into 2 PYRUVATE Molecules b. A small amount of ATP is made (2ATP) c. NAD is reduced to NADH that then takes the hydrogen to the e- transport chain. 2NAD+ + H2 +2e- ---- 2NADH 1. GYLCOLYSIS INPUTS: 1. GLUCOSE ( 6 C) 2. 2 ATP OUTPUTS: 1. PYRUVATE (3C ) 2. 4 ATP 3. 2NADH -Many organisms survive solely on ATP mad during glycolysis when O2 is not available . -Occurs in the Cytosol. 5 -The first half of Glycolysis uses energy 2ATP’s - Each ATP donates a phosphate group to a 3 carbon molecule -The 2nd half of glycolysis nets 4ATP’s -- direct energy use 2NADH ---- chemiosmosis 2 ( 3carbon pyruvates) -- CAC - Pyruvate and NADH formed during glycolysis move into the mitochondria - The folded inner membrane of the mitochondria forms a closed compartment called the mitochondrial matrix. It is protein rich. Copyright 2004 by Alberts, Bray, Johnson, Lewis, Raff, Roberts, Walter. Garland Publishing: Taylor Francis Group. 6 The stepwise oxidation of sugars begins with glycolysis. 7 2. PREPARATION FOR THE CITRIC ACID CYCLE ( KREB CYCLE) - Each 3 carbon Pyruvate gives up one carbon atom as CO2 leaving a two carbon Acetyl group. Hydrogens released are picked up by NAD+ forming NADH. ( NADH will go to etransport chain) INPUTS : 2 PYRUVATE MOLECULES (3 CARBON) Structural Formula C3H3O3pyruvate ion OUTPUTS: - 2 CO2 - 2 Aceytl CoA - 2 NADH 8 - Structure of NAD+/NADH - 3. CITRIC ACID CYCLE: ( Kreb Cycle) - The two carbon Acetyl groups are broken down into 2CO2 molecules - INPUTS Acetyl CoA -OUTPUTS: 1. ATP (2) 2. NADH (6) 3.FADH2 (2) 4.CO2 9 In the CAC , Citric acid is recycled by the attachment of a 2 carbon Acetyl group to Oxaloacetate (4C) . mitochondrion 10 One Turn of the Cycle Acetyl-CoA + 3 NAD+ + FAD + GDP + Pi --- 3 NADH + FADH2 + CoA-SH + GTP > + 3 H2O + 3 CO2 Acetyl-CoA Oxaloacetate Citrate Malate Isocitrate Fumarate a-Ketoglutarate Succinate Succinyl-CoA 11 4.ELECTRON TRANSPORT CHAIN AND CHEMIOSMOTIC ATP SYNTHESIS NADH + FADH2 produced in glycolysis and the citric acid cycle pass hydrogens they carry to a system of electron transport molecules housed in the membrane. Here the hydrogen is separated into H+ and e- and the hydrogen ion is pushed from the matrix to the intermembrane space setting up a hydrogen ion gradient across the inner membrane. 12 -The H+ Gradient provides energy to join ADP + Pi forming ATP -Some electron transport molecules in the chain carry hydrogen atoms while others only carry electrons -The first molecule in the chain lies on the inner surface of the mitochondrial membrane. It can accept two hydrogen atoms from NADH + H+ and transports them through the membrane to the outer surface. 13 H+ builds up on the outside membrane 1 glucose = 64 H+ moved to the outside Note: most energy is made in the e- transport chain via chemiosmotic ATP synthesis. OXYGEN’S ROLE IN RESPIRATION: 1. Oxygen is breathed into the lungs where it enters the bloodstream via the alveoli. 2. It is attached to rbcs on the heme group 3. It goes to each cell in your body via blood 4. Oxygen diffuses into the cell and into the mitochondria 5. e- arriving at the end of the ETC have given up most of their energy. These electrons plus some H+ ions are taken by O2 forming H2O. O2 + 4e- + 4H+ ---- 2H2O Note: w/o oxygen the carrier proteins can’t get rid of the e- so the system backs up 14 Dissociation of water into hydrogen ion and hydroxide ion H2O ---- H+ + OHElectron transport chain lies on the inner membrane of the mitochondria Pg 119 old book KNOW LAST TWO PARAGRAPHS Uncouplers : Substances that permit hydrogen ions to leak through the membrane without going through channels where their energy is used by ATP synthetase. 15 (a) In the presence of excess phosphate and substrate and intact mitochondria, oxygen is consumed only when ADP is added. When all of the added ADP has been convertedinto ATP, electron transport stops and oxygenconsumption ceases. (b) The addition of 2,4-dintrophenol uncouples electron transfer fromATP synthesis. The oxygen is completelyconsumed in the absence of ADP. Uncouplers Enable Organisms to Generate Heat. The uncoupling of oxidative phosphorylation from electron transport generates heat. Hibernating animals and new borne animals (including human beings) contain brown adipose tissue. The adipose tissue is brown due to the high mitochondria content of the tissue. A protein called thermogenin uncouples ATP synthesis from electron transport by opening up a passive proton channel (UCP-1) through the inner mitochondrial membrane. The collapse of the pH gradient generates heat. Proton Motive Force Drives Transport 16 The primary purpose of the proton gradient is to generate ATP by oxidative phosphorylation. The potential energy of the gradient can also be used for active transport. The inner mitochondrial membrane is impermeable to charged molecules. Dinitrophenols used for diet supplement s until several people ran out of ATP and died. Many antibiotics are uncouplers . ex Gramicidin Know steps pg 120 first 2 paragraphs 17 FERMENTATION: (AKA: ANAEROBIC RESPIRATION) 2 TYPES: (Both pathways use glycolysis which nets 2ATP and 2 pyruvates) 1. LACTATE: Bi-product = lactate (lactic acid) 2. ALCOHOL: Bi-product = ethanol - If a cell runs out of oxygen all the transport molecules are soon stuck holding electrons and the chain stops running , the proton gradient runs out, the CAC also backs up and stops . Organisms can still produce small amounts of energy via Anaerobic respiration. 18 19 20 ATP SYNTHASE ENZYME (F0 F1 complex) Structure of ATP synthase, the FO proton channel and rotating stalk are shown in blue, the F1 synthase domain in red and the membrane in grey. An ATP synthase (EC 3.6.3.14) is a general term for an enzyme that can synthesize adenosine triphosphate (ATP) from adenosine diphosphate (ADP) and inorganic phosphate by using some form of energy. This energy is often in the form of protons moving down an electrochemical gradient, such as from the lumen into the stroma of chloroplasts or from the inter-membrane space into the matrix in mitochondria. The overall reaction sequence is: ADP + Pi → ATP These enzymes are of crucial importance in almost all organisms, because ATP is the common "energy currency" of cells. The antibiotic oligomycin inhibits the FO unit of ATP synthase. 21 The electron transport chain in the mitochondrion is the site of oxidative 22 The similarity between intracellular mitochondria and free-living bacteria is striking. The known structural, functional, and DNA similarities between mitochondria and bacteria provide strong evidence that mitochondria evolved from intracellular prokaryotic symbionts that took up residence in primitive eukaryotic cells. (endosymbiont theory) [edit] Mitochondrial redox carriers Prokaryotes similar to Mitochondria / plastids Cyclic DNA Cyclic DNA Small ribosomes Small ribosomes Plasma membrane Plasma membrane 23 FATS AND PROTEINS MAY ENTER THE METABOLIC PATHWAYS OF CELL RESPIRATION. -Both fats and proteins enter cell respiration at the Acetyl level. They can then be used to power cell respiration. Proteins Are de-aminized 24 25 Your body uses approx. 1 LB of ATP per minute That is just less than one mole of ATP /minute 6.02 X 1023 A person will use up their bodyweight in ATP in about 24hrs