Chapter 5 – Short answer
a) Phosphorylation - the addition of phosphate to a chemical compound
b) What are the 3 mechanisms of phosphorylation used by organisms? • Substrate level phosphorylation – ATP is generated when a high-energy phosphate is directly transferred from a phosphorylated compound (substrate) to ADP • Oxidative phosphorylation – electrons are transferred from a group of organic compounds to a group of electron carriers (NAD+ and FAD); occurs in inner mitochondrial of eukaryotes and in plasma membrane of prokaryotes; the sequence of electron carriers is called electron transport chain; the transfer of electrons from one electron carrier to the next releases energy, used to generate ATP from ADP in a process called chemiosmosis • photophosphorylation – occurs in photosynthetic cells, which contain light-trapping pigments (chlorophyll); light cause chlorophyll to give up electrons. Energy released from the transfer of electrons (oxidation) of chlorophyll thru a system of carrier molecules is used to generate ATP.
c) Oxidation – the removal of electrons
d) Chemiosmosis – process whereby energy is released when protons moves along a gradient and is used to synthesize ATP; responsible for most of the ATP generated; process – electrons from NADH pass down the ETC. Carriers in the chain actively transport protons across membranes thru proton pumps. One-directional pumping established a protein gradient; excess H+ on one side of membrane makes that side positively charged compared with the other side, creating a proton motive force…protons on the side of the membrane with higher proton diffuse thru special proton channels that contain ATP synthase; when this flow occurs, E is released and used by the enzyme to synthesize ATP from ADP and Pi
e) Holoenzyme – apoenzyme and cofactor that make a whole, active enzyme
f) Reduction – the gain of electrons
g) fermentation – releases energy from oxidation of organic molecules; doesn’t require oxygen or use the Krebs cycle or ETC; uses an organic molecule as the final electron acceptor
h) respiration – ATP generating process in which molecules are oxidized and the final electron acceptor is an inorganic molecule. 2 types: aerobic/anaerobic; aerobic – for organisms that use oxygen – final electron acceptor is O2; anaerobic – final electron acceptor is inorganic molecule other than O2, or rarely, and organic molecule
i) Coenzyme – cofactor that is a non-protein organic molecule; eg coenzyme A, flavin coenzymes (FAD, FMN), NAD+ and NADP+
3) State what happens during the following steps of carbohydrate metabolism: a) Glycolysis – oxidation of glucose (6-carbon sugar) to two 3-carbon sugars and then to 2 molecules of pyruvic acid with the production of some ATP and energy-containing NADH
b) TCA/Kreb cycle – series of biochemical reactions in which the large amount of potential chemical energy stores in acetyl CoA is released step by step. In this cycle, a series of oxidations and reductions transfer that potential energy, in the form of electrons, to electron carrier coenzymes, chiefly NAD+. The pyruvic acid derivatives are oxidized and the coenzymes are reduced; for every 2 molecules of acetyl coA that enter the cycle, 4 molecules of CO2 are liberated by decarboxylation, 6 molecules of NADH and 2 of FADH2 are produced by oxidation-reduction reactions, and 2 molecules of ATP are generated by substrate-level phosphorylation. Summary - oxidation of acetyl CoA (derivative of pyruvic acid) to carbon dioxide, with the production of some ATP and energy containing NADH, and another reduced electron carrier FADH2 (reduced form of flavin adenine dinucleotide)
c) Electron transport chain – consists of a sequence of carrier molecules that are capable of oxidation and reduction. As electrons are passed thru the chain, there occurs a stepwise release of energy, which is used to drive the chemiosmotic generation of ATP. In eukaryotic cells – ETC...
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