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Transcript
Miss Tee Monday, March 22nd Glycolysis in every living cell break down of one glucose molecule (6Carbon sugar) into (2) 3-Carbon sugar (pyruvate) Yield of ATP low Takes place in cytosol Pyruvate Oxidation Pyruvate transported to matrix Modified into acetyl CoA Prepares molecule for further oxidation in Kreb’s cycle (S-bond unstable) Sir Hans Krebs 1937, awarded Nobel Prize for discovery of cyclic series of enzymatic reactions in mitochondria Def: cyclic series of enzymatic rxns that transfers energy from organic molecules to ATP, NADH, and FADH2 and removes carbon atoms as CO2 8 steps By the end: Original glucose molecule completely consumed 6 carbon atoms leave as 6 CO2 waste CCCCCC CCC + CCC CC + CC + CO2 + CO2 4 CO2 (glucose) (2 pyruvate) (2 acetyl CoA + 2 CO2) (4CO2) Energy stored in 2 ATP (1 ATP/acetyl CoA molecule) Where do you see substrate-level phosphorylation? Step 5 Electron transport chain Consists of series of enzymes on IMM Electrons are released from NADH, FADH2 Enzymes arranged in increasing electronegativity Alternating redox, gaining and losing 2 e Electrons shuttle through ETC, occupying more stable positions Oxygen: final electron acceptor Strips 2 e- from enzyme complex + 2 H+ from matrix = H20 Free energy released used to actively transport protons (H+) through proton pumps By creating a simple chemical gradient, specialized enzyme ATP Synthase is powered to phosphorylate ADP = ATP Miss Tee Monday, March 22nd 3 minutes of silent review Identify areas of weak understanding Consult your colleague Come up with a strategy (mnemonic, acronym, simile) to help you remember Kids Prefer Cheese Over Fried Green Spinach. Kingdom, Phylum, Class, Order, Family, Genus, Species NADH and FADH2 slightly different: FADH2 skips 1st enzyme transfers 2 e- directly to Q FADH2 contributes 2 protons 2 ATP NADH contributes 3 protons 3 ATP What about cytosolic NADH from glycolysis? Cannot access matrix (inner membrane impermeable) Electrons passed to FAD = FADH2 Cytosolic NADH ATP yield different from matrix NADH Why are there many folds of the inner membrane? Limiting factor NAD+ and FAD molecules Converts chemical potential energy into electrochemical potential energy Like a charged battery: accumulation of charge on one side of an insulator Creates electrochemical potential (voltage) H+ unable to diffuse through phospholipid bilayer Forced through specialized proton channels coupled to ATP synthase Drives ADP + Pi ATP Process for synthesizing ATP using the energy of an electrochemical gradient and the ATP synthase enzyme Continual production of ATP by this method dependent upon maintenance of H+ reservoir ATP transported via facilitated diffusion into cytosol, needed for active transport, movement, synthesis reactions *Why do we need O2? To survive, we need ATP from ETC/chemiosmosis We need a maintenance of H+ reservoir We need the flow of e We need O2 to “pull” electrons down the ETC (in their “energy-yielding fall”…like a skydiver) Food Glucose (2) G3P molecules (2) pyruvate molecules Molecule prepped for Kreb’s cycle Acetyl CoA (ticket into Kreb’s) Kreb’s cycle (ATP; NADH, FADH2) Electrons dropped off at the ETC Electrons dropped off at the ETC NADH 3 protons (3 ATP) FADH2 2 protons (2 ATP) CAVEAT: cytosolic NADH ultimately contributes 2 ATP proton gradient established H+ will travel through specialized channel coupled to ATP Synthase Shipped off to wherever it is needed Virtual Cell animation http://vcell.ndsu.edu/animations/atpgradient/m ovie-flash.htm We breathe to acquire O2 to accept the final electron in the ETC. The ETC serves to separate electrons of hydrogen atoms from their protons. The protonmotive force (electrochemical gradient) drives ATP synthesis. Amount of energy consumed by an organism at a given time BMR: basal metabolic rate minimum amount of energy required for organism survival Accounts for 60-70% energy consumed per day When is an individual’s BMR greatest?? Ethanol Fermentation Lactic Acid Fermentation Organisms have evolved ways of recycling NAD+ and allowing glyoclysis to occur in the absence of O2 Fermentation: transfer of hydrogen atoms from NADH to different molecules instead of ETC Hypoxic environment How do we make use of this? Wine, beer, liquor Bread, pastries Soy sauce How does yeast work?? Single-celled fungi (Saccharomyces cerevisiae) Live yeast cells + flour (starch) Ferment glucose, release CO2 bubbles cause dough to rise Ethanol evaporates in high heat in oven Why is most wine 12% alcohol by volume?? Yeast + grape juice (sugars) Ethanol produced Stops at 12%, point at which yeast die Strenuous exercise Muscle cells require >> O2 than provided Hypoxic environment Lactate threshold: Point during exhaustive, all-out exercise at which lactic acid builds up in the blood stream faster than the body can remove it. Anaerobic metabolism produces energy for short, high-intensity bursts of activity (lasting no more than a few minutes) Lactic acid build-up reaches a threshold can no longer be absorbed and, therefore, accumulates This is the lactate threshold What does this mean for athletes? Helps determine how to train, at what pace they can maintain during endurance sports. Lactate threshold can be increased greatly with training Athletes, coaches devise complicated training plans to increase this value Train to endure increasingly higher intensity exercise increase # of mitochondria Convert more glucose potential energy to usable energy (ATP) Having a higher lactate threshold means an athlete can continue at a high-intensity effort with a longer time to exhaustion. How do you accomplish this? Interval training and continuous training Nutrition