Cellular respiration Workshop Key points regarding the following processes 1.Glycolysis 2.Krebs cycle 3.Oxidative phosphorylation The purpose of cellular respiration Provide the cell with energy in the form of ATP (Adenosine Tri-Phosphate) ATP is a temporary energy store When bonds break they release energy, and it is this energy that drives the cell’s processes. ATP----> ADP + iP (inorganic phosphate) + energy The overall reaction C6H12O6 + 6 O2 + 38 ADP +38 Pi → 6 CO2 + 6H20 + 38 ATP 2 types of cellular respiration Aerobic respiration – uses oxygen (like when you do aerobic exercises you use a lot of oxygen – breath hard during running) ●Anaerobic respiration- does not use oxygen less (ATP) produced ●Reduction – loss of electron ●Oxidation – gain of electron ● Glycolysis The hormone insulin signals to the cell’s plasma membrane to transport glucose into the cell ●Glycolysis means the breakdown of the glucose molecule ●Glucose contains 6 carbons C6H12O6 ●The process breaks glucose down into 2 molecules of Pyruvate ●Pyruvate is the ionized form of pyruvic acid ●Each molecule of pyruvate contains 3 carbons ●Ion = electrically charged atom or molecule ●Anion = negative charged atom ●Cation = positively charged atom ● Glycolysis This process occurs in the cytosol ●This process does not require oxygen and produces no CO2 ●Produces 4 molecules of ATP ●However 2 ATP are used so only 2 of the original 4 are made available to the cell ●the process also produces ● 2 NADH + 2 H+ ●NAD+ is a co-enzyme that becomes reduced ●Reduction is the addition of an electron to a molecule ●Most of the electrons from glucose are initially transferred to NAD+ ●Glucose has hydrogen and the hydrogen gives up electrons to NAD+ ●2 H = 2e- + 2H+ ●2 NAD+ + 4 e- + 4 H+ → 2 NADH + 2 H+ ● ● GLYCOLYSIS The overall reaction ●Glucose + 2 NAD+ +2ADP + 2Pi → ●2 pyruvate + 2 NADH + 2 H+ + 2 ATP ●Lets break it down looking at which reactants become which products ●In this overview we will ignore H2O ● Glucose → 2 pyruvate ●4 ATP – 2 ATP used → 2 ATP or ●2 ADP + 2 Pi → 2 ATP ●2 NAD+ + 4 e- + 4 H+ → 2 NADH + 2 H+ ● The linking step Occurs in the mitochondria- pyruvate can only enter the mitochondria in the presence of oxygen ●The linking step turns pyruvate into Acetyl Co-enzyme A so it can enter the krebs cycle ●The two pyruvate from glycolysis continue to the linking step that converts each molecule into Acetyl Co-enzyme A ●2 pyruvate -→ 2 Acetyl Co-enzyme A ●This step also produces → 2NADH + 2 H+ ●In addition the linking step produces 2 CO2 ●The CO2 lost is a result of the carboxl groups ( --COO-) which is already fully oxidized and has little energy is removed from pyruvate and given off as a molecule of CO2 ● The linking step Pyruvate is turned into acetyl coA, in the process giving off a CO2 ●This means that the resulting molecule of acetyl coA only ● has 2 carbons as it enters the krebs cycle ●COO- (carboxl group) is an anion, it becomes oxidized to form CO2 Krebs Cycle The krebs cycle is also refered to as the citric acid cycle or the tricarboxylic acid cycle ●The 2 Acetyl Co-enzyme A produced during the linking step can now enter the Krebs cycle ●Each revolution of the krebs cycle is commonly referred to as one spin ●1 glucose → 2 pyruvate → 2 Acetyl CoA ●Each acetyl coA participates in one revolution of the krebs cycle ●So the krebs cycle spins twice for each glucose ● Krebs Cycle The krebs cycle occurs in the mitochondrial matrix ●One spin produces 2 CO2 however uses no oxygen, so 4 for each glucose ●One spin produces 1 ATP, so 2 for each glucose ●3 NADH and 1 FADH2 are produced per spin, so 6 NADH and 2 FADH2 ● This accounts for 8 of 12 reduced co-enzymes from the krebs cycle ●However there where 2 NADH produced during the linking step, so that brings the total to 10 of 12 reduced co-enzymes ●The other 2 co-enzymes are 2 NADH that came from glycolysis bringing the total to 12 reduced co-enzymes ●10 NADH and 2 FADH2 ● KREBS CYCLE The overall reaction for the krebs cycle including the linking step ● 2 pyruvate + 8 NAD+ + 2 FAD + 2 ADP + 2 Pi + 6 H2O → ●6 CO2 + 8 NADH + 8 H+ + 2 FADH2 + 2 ATP ●The purpose of the krebs cycle is to take glucose from the food we eat that has been modified by glycolysis and the linking step and oxidize it. Which basically means steal the electrons. Once the electrons have been removed from acetyl coA they are donated to NAD+ and FAD. Addition of electrons is termed reduction. That is why it is said that the krebs cycle produces 10 out of 12 reduced co-enzymes ● Oxidative Phosphorylation Occurs within the inner mitochondrial matrix ●Involves 2 processes simultaneously ●1. Electron transport chain ●2. Chemiosmotic coupling ●Chemiosmosis means energy stored in a hydrogen concentration gradient across a membrane is used to perform work for the cell, in this case synthesis of ATP ● Oxidative Phosphorylation This process requires oxygen ●During the krebs cycle NAD+ and FAD where reduced (electrons where added to them) ●Now they will donate their electron to the electron transport chain (oxidation) ●The electron transport chain is a series of proteins located in the inner mitochondrial membrane ●These proteins include iron sulfur proteins, co-enzyme q and cytochromes ●NADH donates its electron to FMN (Flavin Mono-Nucleotide) ●FADH2 donates its electron to coenzyme Q ● Electron transport chain NADH and FADH2 give up their electrons to a component of the electron transport chain. Then these electrons are passed to the next component of the chain. ●Each time an electron is passed from one component to the next they lose some energy ●This energy is used to move hydrogen ions against their concentration gradient into the intermembrane space ● The last protein in the chain is cytochrome a3 ●once the electrons reach cytochrome a3 they react with hydrogen ions to form hydrogen ●hydrogen then reacts with oxygen to form water ●-e + H+ = hydrogen ●oxygen is the ultimate electron acceptor ●it is very important for oxygen to be present ●without oxygen the electrons have nowhere to go, and the electron transport chain becomes overwhelmed. ● Chemiosmotic coupling This process produces the ATP ●Each time an electron moves from one component of the electron transport chain to the next, energy is released ●This energy is used to more hydrogens against their concentration gradient, from the matrix to the intermembrane space of the mitochondria. ●This process requires energy because the hydrogen ions are moving against their concentration gradient. ●Once the hydrogen ions have been moved to the intermembrane space they can move down their concentration gradient. ● DO NOT CLOSE THIS PLEASE When a molecule moves down its concentration gradient it does not require energy The hydrogen ions move from the intermembrane space to the matrix through a protein called ATP synthase. ATP synthase is an enzyme located in the inner mitochondrial membrane