Cellular Respiration PDF

Cellular Respiration: The Story The purpose of cellular respiration is to transfer the chemical energy from glucose to ATP. Lets get started with Cellular Respiration….. Stage 1: Glycolysis Where does it happen? In the Cytoplasm of the cell Does it need Oxygen? Glycolysis is an anae...

Cellular Respiration: The Story The purpose of cellular respiration is to transfer the chemical energy from glucose to ATP. Lets get started with Cellular Respiration….. Stage 1: Glycolysis Where does it happen? In the Cytoplasm of the cell Does it need Oxygen? Glycolysis is an anaerobic process (no O2) What does it do? 1 (6C) glucose molecule is broken down into 2 (3C) pyruvates (a.k.a. Pyruvic acid) Energy Produced? For each Glucose broken down, there is a net gain of 2 ATP (4 ATP are produced but two are used in the process) Energy in the form of electrons and hydrogen is carried in NADH 2 ATP 2 ADP Glucose (6C) Fructose 1, 6 Bisphosphate (6C) 4 ADP 4 ATP 2 NAD 2 NADH 2 X Pyruvate (2 x 3C) 2 ATP = 62 kJ/mol 2.2% Efficient 1 molecule of glucose = 2870 kJ So what happens when there is no Oxygen???? Fermentation: Lactic Acid Alcoholic Lactic Acid Fermentation - Occurs in Bacterial cells - In muscle cells under certain conditions (oxidized back to pyruvate when O2 is available) Alcoholic Fermentation - in yeast cells - Pyruvic acid  acetaldehyde  Ethanol NAD+ goes back to reaction to continue ATP synthesis Let’s remember the Mitochondria (the energy organelle) Stage 2: Pyruvate Oxidation 2 Pyruvate are transported into the Matrix of the mitochondria CO2 CoA Pyruvate (3C) Acetyl Co-A (2C) NAD+ NADH 2 Pyruvate + 2 NAD+ + 2CoA ----> 2 Acetyl-CoA + 2 NADH + 2H+ + 2CO2 Stage 3: Kreb’s Cycle (a.k.a. The Citric Acid Cycle) Where does it happen? In the Mitochondrial Matrix Does it need Oxygen? Absolutely!!! No oxygen no Kreb’s Cycle What does it do? Transfer energy to NAD and FAD which are reduced to NADH and FADH2 It’s a cyclical reaction, a series of redox reactions. Occurs twice for every molecule of Glucose Energy Produced? 6 NADH, 2 FADH2 and 2 ATP are produced Acetyl-CoA + Oxaloacetate + ADP + P + 3 NAD + FAD CoA + Oxaloacetate + 2CO2 + ATP + 3 NADH + FADH2 Lets Review: - The glucose molecule is now completely dismantled. - Some of the energy is in the form of ATP but MOST is in the electrons of NADH and FADH 2 NADH 2 NADH Glycolysis 2 ATP Pyruvate Oxidation 2 CO2 2 Pyruvate 2 Acetyl CoA 4 CO2 Kreb’s Cycle (CAC) 6 NADH 2 FADH2 2 ATP Stage 4: Electron Transport Chain Where does it happen? On the inner mitochondrial membrane Does it need Oxygen? Oxygen serves as the final electron acceptor! What does it do? NAD and FADH lose the H atom electrons to a series of proteins in the inner mitochondrial membrane (arranged in order of increasing electronegativity) Energy Produced? Energy released is used to pump protons into the intermembrane space which is then used to generate ATP.  Each compound is reduced by gaining 2 electrons (GER) from the protein before it.  Then each compound is oxidized by losing the 2 electrons (LEO) to the next protein.  Electrons are finally passed to oxygen (very electronegative) and along with 2H+ from the matrix  form H2O 2H+ + ½ O2 + 2e-  H2O  The energy released is used to pump 2H+ (protons from intermembrane space, through three proton pumps, into the mitochondrial matrix) EVERY NADH PUMPS 6 H+ ACROSS  3 ATP EVERY FADH2 PUMPS 4 H+ ACROSS  2 ATP Chemiosmosis  Protons accumulate in the INNER MEMBRANE SPACE creating an electrochemical gradient  Protons must diffuse through a protein channel in membrane (ATPase). As they do they release energy (proton motive force) which is used to synthesize ATP  ATP synthesis by chemiosmosis is coupled with electron transport, and both are dependent on the availability of electrons (from glucose) and oxygen. matrix Inner mitochondrial membrane Intermembrane space FOR EVERY 2H+ PUMPED ACROSS THE MEMBRANE BY THE ETC 1 ATP IS PRODUCED. Theoretical Yield of ATP: from 1 molecule of Glucose Glycolysis 2 ATP 2 ATP 2 NADH 4 ATP FADH2 (to cross membrane it is converted into FADH2) Pyruvate Oxidation 2NADH 6 ATP Kreb’s Cycle 2 ATP 2 ATP 6 NADH 18 ATP 2 FADH2 4 ATP 36 ATP See Chart on Page 114 In the end the actual yield is approximately 30 ATP. - some H+ leak through the intermitochondrial membrane, not through the ATPase - Some H+ are used by the cell for other activities Overall Efficiency: 30 ATP x 31 kJ/ATP x 100 = 32% 2870 kJ Time for some fun!!! Section 2.2 Questions on page 115 #1-16, 18, 19 a, c