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Date _________ • Chapter 7~Cellular Respiration: Harvesting Chemical Energy or The Biochemistry of heterotrophs Principles of Energy Harvest Organisms who can’t make their own food are called heterotrophs. This means they must convert the the energy found in the organic compounds they eat. They do this thru a series of catabolic and anabolic redox pathways. Overall: C6H12O6 + 6O2 ---> 6CO2 + 6H2O + E (ATP + heat) Redox reactions • • More Oxidation-reduction Reducing agent: • Oxidizing agent: • So, in cell respiration: Glucose is oxidized (reducing agent) and oxygen is reduced. (oxidizing agent) • (The main Redox reactions) So make connections! So let’s brainstorm what heterotrophs are going to do in their biochemical pathways….. Compared to plants • Similarities • Differences Now we have to really be careful! C6H12O6 Why ATP? • • • • Less stable=higher NRG potential Recyclable (rechargeable) (ADP, AMP) 36 ATP for every 1 glucose More easily stored and retrieved Double H baby sitters required!!! Now we are really “playing with fire”!!! • NAD+ (nicotinamide adenine dinucleotide) And FAD+ (flavin adenine dinucleotide) • Both collect electrons from the intermediate reactions and shuttle electron (-) and proton (+) ions across membranes. • Oxygen eventually collects all the hydrogen atoms. • FAD is a better carrier, but more energy expensive to make Cellular respiration Overview • Glycolysis: cytosol; degrades glucose into PGAL which becomes pyruvate after each PGAL loses an H (collected) • Kreb’s (Citric) Cycle: mitochondrial matrix (just inside the mito); pyruvate into carbon dioxide, more H’s lost and collected • Electron Transport Chain: inner membrane of mitochondrion; H electrons passed to oxygen Glycolysis (what you need to know) • 1 Glucose +2 ATP +4 NAD+ 4 ADP + 4 P 2 PGAL + 2 NADH 2 pyruvate + 4 ATP + 4 NADH + 2 ADP+ 2 P • So, 1 glucose = 2 pyruvate, 2 ATP (net) and 4 NADH • Energy investment: Cell “burns” 2 ATP (ATPADP) to initiate process, as glucose is stable and won’t catabolize on its own. • Energy payoff : 1) 4 ATP are produced by substrate-level phosphorylation (NET gain of 2 ATP) 2) 4 NAD+ are reduced to NADH, 3) 2 pyruvates (C3H4O3) that can still be used. • Anaerobic and it Occurs in the cytosol (Pyruvate and pyruvic acid are the same thing) • Random pic alert! Glycolysis QuickTime™ and a Cinepak decompressor are needed to see this picture. Stage or phase 2: Citric Acid Cycle (Kreb’s Cycle) • First, unstable pyruvate must be temporarily stabilized. To do this, pyruvate is combined a helper called “co-enzyme A” (CoA) to form a compound called Acetyl-CoA. We must release CO2 to do this and release some hydrogen so allow different NAD+ to pick them up as NADH. • This binding to co-enzyme A (CoA) accomplishes 2 important things, 1-it increases the permeability into the mitochondrion and 2- slows degradation of the pyruvate * • * 2 Carbon acetyl CoA binds to 4 Carbon oxaloacetate to form a 6 Carbon Citric Acid (citrate)…COOL! CAC continued • 2 carbon Acetyl CoA + O2 + NAD + FAD + ADP + P + oxaloacetate Citrate + 4NADH + 1ATP +1 FADH2 + 4 CO2 + CoA • Multiple the numbers by 2 as 1 glucose = 2 pyruvates • Again (like Glycolysis, only using substrate level phosphorylation) • Aerobic as oxygen required to remove carbon in the form of CO2 (Bohr’s Shift) Cyclic as we regenerate CoA each round • Occurs in the inner space of the mitochondrion called the matrix (See next diagram) The mito! CO2 and O2-Bohr’s Shift pH, temp, blood pressure HOMEOSTASIS • Man that’s a big head…..JK Now...why did we collect all those H’s??? To harness their power!!! Third phase or stage: Electron transport chains • Uses electron carrier molecules (NAD and FAD) along with special membrane proteins embedded in the cristae to safely move Hydrogen’s electron and proton power (proton motive force) ultimately to ATP Synthase. • Ubiquinone, Cytochrome C, NADH reductase • Use the proton motive force to make even more ATP . Many shuttle stations due to the folding of the cristae • Will use oxygen to drive the movement of hydrogen ions from carriers so we call this oxidative phosphorylation. • Hydrogen’s proton is moved through the cristae’s proteins and to waiting oxygen, while the resulting electrons follow but are shuttled through specific places in the cristae first. They too eventually find the water! • http://video.search.yahoo.com/yhs/search;_ylt=AwrTcdWlL7dYaiEAqVgPxQt.?p=electron+transport+chain&fr=yhs-iryfullyhosted_003&fr2=piv-web&hspart=iry&hsimp=yhsfullyhosted_003&type=wncy_popjar_15_34&vm=r#id=40&vid=86c40148754ea83030746b806a4a37d7&action=view ETC=Chemiosmosis • When we are done, we will make about 34 ATP and water for the energy investment of ZERO! Remember, this ability to use ions is brought to you by the cristae!! • Semipermeable membrane…. • Allows what to cross? • Why important here?? Electron transport chain Review/ATP made during Cellular Respiration • Glycolysis: 2 ATP (substrate-level phosphorylation) • Citric (Kreb’s) Cycle: 2 ATP (substrate-level phosphorylation) • Electron transport: (oxidative phosphorylation) 2 NADH (glycolysis) = 6ATP 2 NADH (acetyl CoA) = 6ATP 6 NADH (Citric) = 18 ATP • 2 FADH2 (Citric) = 4 ATP • 38 TOTAL ATP/glucose Whew!!!! Related metabolic processes • Fermentation: No O end products are ethanol, CO2 OR lactic acid and CO2 Glucose pyruvate to ethanol OR lactic acid~ and CO2 (anaerobic) • Facultative anaerobes (yeast/bacteria) 2 All roads…..