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BIOL125_Ch8 Lecture Notes

BIOL125_Ch8 Lecture Notes - BIOL 125(Microbiology Lecture...

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Unformatted text preview: BIOL 125 (Microbiology) Lecture Notes Chapter 8: Microbial Metabolism 1. MICROBIAL METABOLISM a. Metabolism – sum of all chemical reactions and physical changes (ex. cell growth, colony growth) that are taking place in a living cell. b. Chemical Reactions i. Chemical reactions take place in a cell by constantly breaking old bonds and making new bonds (i.e. the rearranging of molecules). ii. A chemical reaction in a cell results from the collision of reactant molecules, which produces a product. 1) Reactants – molecules entering a chemical reaction. 2) Product – molecules formed after a chemical reaction. iii. Two types of chemical reactions: catabolism and anabolism. 1) Catabolism – complex molecules are broken down into simple molecules. a) Releases energy. b) Chemical reactions generate energy in the form of ATP to conduct metabolic activities. 2) Anabolism – complex molecules are built from simple molecules. a) Requires energy. b) Chemical reactions generate complex molecules for the cell to grow. iv. The speed of chemical reactions can be increased in three ways: 1) Heating of increasing thermal energy (kills the cell). 2) Increasing the concentration of the reactants (not possible in a living cell). 3) By lowering the activation energy with the help of enzymes. c. Activation Energy i. Activation Energy – minimum energy required to start a chemical reaction. ii. Enzymes mediate the chemical reaction in a cell by increasing the chances of a collision between substrate (reactant) molecules. 1) Enzymes increase the rate of conversion of substrate to product, thus reducing the activation energy. File: cdcd2b26d1dd3dc2164099a88e44f1f7c224a921.doc Updated 8/14/09 Microbiology Lecture Notes Chapter 8 Page 2 2. ENZYMES a. Enzymes – proteins encoded by genes on the chromosome. They are catalysts that help convert substrate to products. QuickTime & and a decompres or are ne ded to se this picture. b. In an enzymatic reaction, enzymes do not undergo any change, but merely provide a place where the substrates (reactants) can interact to produce a product. c. All enzymes are synthesized in the cytoplasm of the cell. d. Active Site (Catalytic Site) – where the substrate binds to the enzyme. i. The site is very specific for a given substrate (reactant). ii. Some enzymes can have more than one active site, meaning they can bind with different substrates. iii. The bond formed between an enzyme and a substrate is very weak and reversible. iv. The binding generates changes in the substrate leading to the formation of products. e. Enzymes can be simple enzymes or holoenzymes. i. Simple Enzymes – consist of protein alone. ii. Holoenzymes (Conjugated Enzymes) – contain protein and nonprotein molecules....
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BIOL125_Ch8 Lecture Notes - BIOL 125(Microbiology Lecture...

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