BIOL125_Ch8 Text Notes

BIOL125_Ch8 Text Notes - BIOL 125 (Microbiology) Text Notes...

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BIOL 125 (Microbiology) Text Notes Chapter 8: Microbial Metabolism 1. THE METABOLISM OF MICROBES a. Cellular reactions fall into two major categories: catabolism and anabolism. i. Catabolism – larger molecules are degraded or broken down into smaller molecules, usually with the release of energy. ii. Anabolism (Biosynthesis) – larger molecules are build from smaller molecules, which is usually driven by energy from catabolism. b. Enzymes: Catalyzing the Chemical Reactions of Life QuickTime and a decompres or are ne ded to se this picture. i. Enzyme – a special class of protein (biocatalyst) that increase the rate of a chemical reaction without becoming part of the products or being consumed in the reaction. 1) Most uncatalyzed metabolic reactions do not occur fast enough to sustain cell processes. ii. How Do Enzymes Work? 1) Energy of Activation (Activation Energy) – resistance to a reaction, which must be overcome for a reaction to proceed. a) In the lab, overcoming this initial resistance can be achieved by: i) Increasing thermal energy (heating) to increase molecular velocity. ii) Increasing the concentration of reactants to increase the File: 124a64dbb1ab8f7564ac9adb558ec42f0dfb80dd.doc Updated 8/14/09
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Text Notes Chapter 8 Page 2 rate of molecular collisions. iii) Adding a catalyst. 2) Enzymes promote a reaction by serving as a physical site upon which the reactant molecules ( substrate ) can be positioned for various interactions. 3) Enzyme speed is the number of substrate molecules converted per enzyme per second. iii. Enzyme Structure. 1) The primary structure of all enzymes is protein (with some exceptions). 2) Enzymes can be classified as simple or conjugated. a) Simple Enzymes – are complied of protein alone. b) Conjugated Enzymes (Holoenzymes) – consist of a protein ( apoenzyme ) and one or more cofactors . i) Cofactors – either organic molecules (coenzymes) or inorganic elements (metal ions) that conjugated enzymes need to function. ii) In some enzymes, the cofactor is loosely associated with the apoenzyme by noncovalent bonds; in others, it is linked by covalent bonds. iv. Apoenzymes: Specificity and the Active Site. 1) Apoenzyme – the protein part of an enzyme, as opposed to the nonprotein or inorganic cofactors (from the text Glossary). 2) Apoenzymes exhibit levels of molecular complexity called primary, secondary, tertiary, and quaternary organization. a) The first three levels arise when a single polypeptide chain undergoes an automatic folding process and achieves stability by forming disulfide and other types of bonds. 3) Active Site (Catalytic Site) – the actual pocket where the substrate binds. There can be one or several sites. v.
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This note was uploaded on 08/12/2009 for the course BIOL 125 taught by Professor Dr.sujathapamula during the Spring '09 term at San Jacinto.

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BIOL125_Ch8 Text Notes - BIOL 125 (Microbiology) Text Notes...

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