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Respiration! • Chapter 9~ • Cellular Respiration: Harvesting Chemical Energy • Great Animation (show at end too) Big Picture! • Big Picture: Glucose has Stored Energy, Cells must Convert it to ATP (the fuel of the cell) – This happens through a series of energy releasing redox reactions that we will learn about shortly. • Overall Equation for cellular respiration: C6H12O6 + 6O2 ---> 6CO2 + 6H2O + E (ATP + heat) Redox reactions • Oxidation-reduction • Oxidation (i.e. to be oxidized) is e- loss; – Or oxygen gain • Reduction (i.e. to be reduced) is e- gain; – Or hydrogen atom gain • LEO GER • Redox reactions release energy!!! Cellular respiration • Cell Respiration = the controlled release of energy from organic compounds in cells to form ATP! STAGES: • Glycolysis: location: cytoplasm • Link Reaction: • Krebs Cycle: location mitochondrial matrix • Electron Transport Chain location: inner membrane of mitochondrion Glycolysis • Overall: 1 Glucose (6C)2 pyruvate molecules (3C each) • 10 total steps but we will focus on 4 stages: – Phosphorylation • cell uses ATP to phosphorylate hexose sugar (glucose) making a Hexose biphosphate – Lysis • Hexose is split in half to make two triose sugars – Oxidation • Each triose loses electrons and hydrogens • These are transferred to NAD+ to make NADH and H+ – ATP formation • ATP is produced by substratelevel phosphorylation • 2 Pyruvates are made. 2 inorganic phosphates Animation http://highered.mcgraw-hill.com/sites/0072507470/stud Glycolysis continued • Net energy yield per glucose molecule: 2 ATP plus 2 NADH + H+; • Note: occurs aerobically or anaerobically; also no CO2 is released For Reference: The 10 steps of Glycolysis After Glycolysis… Glycolysis can occur aerobically or anaerobically QuickTime™ and a Anaerobic Respiration= Aerobic Respiration= Cinepak decompressor are needed to see this picture. •No oxygen •Requires oxygen •Occurs in cytoplasm •Occurs in mitochondrion •Pyruvate converted to either •Pyruvate broken down into lactate OR ethanol and CO2 CO2 and H2O •No further yield of ATP •Large yield of ATP The Next Slides deal with Aerobic Respiration … Aerobic Respiration Steps: 1. Link Reaction 2. Krebs Cycle (Citric Acid Cycle) 3. Electron Transport Chain (ETC) The link reaction •Each pyruvate is converted into acetyl CoA •CO2 is released; (pyruvate is decarboxylated) •NAD+ NADH + H+ •Note: NAD+ gets reduced •NADH is an electron carrier Krebs/Citric Acid Cycle • From this point, for each turn, 2 C atoms enter (acetyl CoA) and 2 exit (carbon dioxide) • Oxaloacetate is regenerated (the “cycle”) • For each acetyl CoA that enters: – 3 NAD+ reduced to 3 NADH; – 1 FAD reduced to FADH2 – 1 ATP molecule produced Electron transport chain • The ETC carries electrons from carrier molecules (NADH & FADH2) down to oxygen (the final electron acceptor!) – The ETC pumps H+ into the intermembrane space! • ATP synthase: produces ATP by using the H+ gradient as H+ flows back into the matrix • Chemiosmosis: The production of ATP using the energy of hydrogen ion (proton) gradients across membranes. • This whole process of making ATP is also called oxidative phosphorylation (b/c it uses oxygen as the final electron acceptor) • OXYGEN is the final electron acceptor. It gets reduced to make H2O Electron Transport • • NADHFMN iron sulfur protein (FeS) a lipid called ubiquinone (Q) cytochromes O2 FADH2 starts donating its electrons to the iron sulfur protein. Therefore it is able to make less ATP than NADH. • http://highered.mcgrawhill.com/sites/0072437316/student_view0/chapter9/anim ations.html# • ATP synthase animation • ATP Review: Cellular Respiration • Glycolysis – 2 ATP (substrate-level phosphorylation) • Kreb’s Cycle: 2 ATP (substrate-level phosphorylation) • Electron transport & oxidative phosphorylation: – 32-34 ATP as follows: • 10 NADH used to make 30ATP • 2 FADH2 used to make 4 ATP • 38 TOTAL ATP/glucose Great Animation The Mighty MITOCHONDRION! (draw and label) Mitochondria (Structure and function) Structure Cristae Small space between inner and outer membranes Fluid matrix Function What if there’s no oxygen? (anaerobic respiration) • Glycolysis • Fermentation: alcohol~ pyruvate is converted to ethanol and CO2 (in yeast and bacteria) lactic acid~ pyruvate is converted to lactate (in animals) Why Fermentation? *Fermentation allows glycolysis to continue •It recycles NAD+ (a necessary oxidizing agent required for the continuation of glycolysis) • see next slide for review of glycolysis… 2 inorganic phosphates End of IB • The next slides are interesting but not in the syllabus What if there’s no Glucose? • Respiration still can continue • Beta-oxidation: lipid catabolism to acetyl CoA. • Amino acids – Converted to intermediates in glycolysis and Krebs cycle Control of Respiration • Feedback Inhibition • Examples – Phosphofructokinase (Enzyme 3 in Glycolysis) • allosterically inhibited by ATP • Allosterically activated by AMP (derived from ADP) – Why? Oxidizing agents in respiration • NAD+ (nicotinamide adenine dinucleotide)= initial electron acceptor (oxidizing agent) • NAD + is reduced to NADH • Oxygen is the eventual eacceptor (The ULTIMATE Oxidizing Agent) • Facultative anaerobes don’t require oxygen but can live with it. (yeast/bacteria) • Obligate anaerobes – Can’t live with oxygen – Clostridium botulinum (botulism bacterium)