MCB 100 1st Edition Lecture 17 Outline of Last Lecture I. Enzymes- what they can/cannot doII. ATP- the energy molecule of cells Outline of Current Lecture I. What are some ways that a cell uses ATP? II. Respiration a. Glycolysis b. Krebs cycle c. Electron transport chain d. Oxidative phosphorylation Current LectureI. What are some ways that a cell uses ATP?A. Substrate activationi. For glucose to be broken down it must be activated by the attachment of 2 phosphates. The cell converts glucose to glucose-1, 6-bisphosphate, which can be broken down to yield energy and form ATPii. ATP and similar nucleotide triphosphates are the activated building blocksof nucleic acid biosynthesisiii. Energy from ATP is used to attach amino acids to tRNA molecules. (key energy consuming step in protein biosynthesis) B. Power cellular motioni. Energy from ATP is used to make flagella rotate and muscle fibers contract. ii. Energy from the hydrolysis of a similar compound, GTP, is used to make a ribosome move along a strand of mRNA in a specific direction; energy from ATP can be used to make GTP B. Pump ions or other molecules across a membranei. Active transport to take in nutrients or excrete wastes A. Cells make most of their ATP in 2 ways: i. Substrate-level phosphorylation: energy to form a high energy phospho-anhydride bond can come from the hydrolysis of a higher energy bond such as a mixed anhydride bond (carboxylic acid- phosphate) or a phospho-enol bond)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.a. Requires the sacrifice of a chemical bond that has a higher energy than the high energy bond of ATPb. An enzyme transfers a phosphate group from an organic compound to ADP to form ATP. The cell must form a metabolic intermediate that has a very high energy bond joining a phosphate group to an organic compound before the SLP occursc. S~P + ADP --> S + ATP d. Enzymes that catalyze the transfer of the phosphate groups in SLP are called "kinases". SLP reactions take place in the cytoplasm and involve water-soluble enzymes. ii. The H+ ATPase (proton-ATPase): This method uses the potential energy of the proton motive force (PMF). Also known as the chemoosmotic theory or oxidative phosphorylation. a. There must be a membrane separating two compartments that have a difference in the concentration of protons b. Protons flow through the portal from the side with the highest concentration to the side with the lowest. Energy from the flow of protons can be used to synthesize ATP c. Proton gradients can be established using the chemical reactions of respiration via the electron transport chain, or through a photo-activated electron transport chainII. Aerobic Respirationa. Oxidation of glucose to carbon dioxide and waterb. Steps: i. Glycolysis1. Makes: 4 ATPs2. Uses: 2 ATPs 3. Profit: 2 ATPs 4. 10 reactions, makes 2 ATPs per glucose 5. 1 glucose molecule --> 2 molecules of pyruvate 6. Pyruvate dehydrogenase reaction: 2 molecules + 2 molecules --> 2 acetyl-CoA + 2 CO2 of pyruvate of Coenzyme A ii. Krebs cycle1. Makes: 2 GTPs 2. 8 NAD+ --> 8 NADH 3. 2 FAD --> 2 FADH2 4. 2 ATPs are generated by substrate-level phosphorylation5. Can happen in the absence of air. Oxygen atoms come from water molecules i. Electron transport chain and oxidative phosphorylation 1. 2 FADH2 --> FAD2. 10 NADH --> NAD+ 3. Makes PMF that can make 34 ATPs4. Oxidative phosphorylation = a series of redox reactions involving membrane bound enzymes and electron carriers that results in the re-oxidation of NADH + H+ back to NAD+, the reduction of O2 to H2O and the production of about 34 ATPs per glucose; it yields a proton motive force (PMF) that is sufficient to produce about 3 ATPs per NADH oxidized and 2 ATPs per FADH2 oxidized a. PMF- a proton gradient across a membrane can be used to drive several processes, including: ATP synthesis, active uptake of nutrients, ion pumps, and flagella rotation 2. Electron transport chain (ETC) is a series of enzymes and electron carriersembedded in a membrane. The ETC is located in the mitochondrial membrane in eukaryotic cells and in the cytoplasmic membrane in bacteria a. NADH + H+ is oxidized to NAD+ b. Electrons are passed from carrier to carrier, protons are pumped across membranec. Oxygen is reduced to water, in aerobic respiration oxygen is the terminal electron acceptor. Protons flow through ATP synthase and generate ATP from ADP + Pi d. 2 NADH + 2 H+ + O2 --> 2 NAD+ + 2H2O b. Aerobic respiration yields about 38 ATPs per glucose molecule
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