MCB 100 1st Edition Lecture 15 Outline of Last Lecture I. Mathematical considerations of bacterial growthA. Total count vs. viable count B. Generation time C. Growth rate II. Methods of enumerating microorganismsA. Direct microscopic count B. Membrane filter methodC. Most probable number D. Dry-weight method III. Turbidity Outline of Current Lecture I. MetabolismA. Anabolic and catabolic reactions II. Enzymes III. Bacterial enzymes IV. General steps of an enzyme catalyzed for biochemical reactions V. Enzyme classes VI. Metabolic pathways and metabolic intermediates VII. Simple proteins and conjugated proteins VIII. Conditions that can affect the activity of an enzyme Current LectureI. Metabolism: the sum of all the chemical reactions that occur in an organism (and there are a few thousand different chemical reactions going on in a typical cell) A. Anabolic reactions i. Involves in the building up of biological molecules (DNA, proteins, lipids, polysaccharides, and precursor molecules) ii. Produce the complex molecules that cytoplasm is made ofiii. Associated with growthiv. Consume energy in the form of ATP B. Catabolic reactionsi. Release energy that is used to produce ATP ii. Involved in the breaking down of complex molecules to yield simple molecules that the cell can use as synthetic raw material 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.II. Enzymes- The biological catalysts of biochemical reactions A. Most enzymes are proteins but there are some RNA molecules with catalytic activityB. Enzymes are made by living cells and are absolutely required for growth. Impairmentof enzymes (sometimes just one) can cause death of a cell (or a drastic change In its activity)C. An enzyme destabilizes chemical bonds in the substrates (reactants) and promotes formation of the activated complex, a state that is in between the substrates and the products D. A typical enzyme can make a reaction go 100 million times faster E. Typical cells have about 2000-3000 different enzymesF. The lock and key model for enzyme activity refers to the need for structural compatibility b/w the substrate and the enzyme. Enzymes are very specific catalysts. A given enzyme will recognize only one type of substrate molecule and cnvert it to only one particular type of product. The shape of the active site of an enzyme is complementary to the shape of the substrate. G. A catalyst = a substance that helps a chemical reaction occur faster; the active site ofan enzyme is the catalytic site (usually a pocket or cleft where the substrates bind)i. A catalyst accelerates chemical reactions by reducing the activation energy barrier. Reactant molecules bind to the surface of a catalyst and are converted to products ii. Catalysts are not consumed by chemical reaction that they accelerate iii. Active site/catalytic site: 1. Functional groups on amino acids that surround the active site bind to thesubstrate molecules, create stress on the old chemical bonds and encourage formation of new chemical bonds leading to formation of the product 2. Some enzymes convert a single substrate to a single product but many enzymes use 2 or more substrates and produce 2 or more products B. 3 general areas in/around a cell where enzymes are found i. Outside cell, in the culture media: excreted enzymes (exo-enzymes). Some enzymes help to digest large molecules such as starch to release smaller molecules like sugars that can be absorbed by the cell. Other exo-enzymes may be toxins that cause disease in the host animal (ex. Streptococcus pyogenes excretes an exoenzyme called hemolysin which breaks open red blood cells- this releases nutrients for the bacteria ii. Embedded within the cytoplasmic membrane: some important enzymes involved in respiration are found in cytoplasmic membrane. Some of these enzymes pump ions across membrane. Others that are embedded within the membrane include those that actively pump nutrients into the cell and waste products out. Some cause metabolic changes within the cell in response to external signals.iii. In cytoplasm of bacterial cell: there are more than 1000 different enzymes at work in cytoplasm. Some of them synthesize amino acids, proteins,nucleotides, nucleic acids, sugars, etc. Others break down nutrients to simple compounds while producing energy in the form of ATP II. Bacterial enzymes A. Enzymes of excreted hydrolytic enzymesi. Lipase: an exoenzymes for digesting fats ii. Amylase: an exoenzyme for digesting starch iii. Gelatinase: an exoenzyme for digesting proteinII. General steps of an enzyme catalyzed biochemical reactions: A. Substrate(s) bind to the enzyme at the active siteB. Flexing of the enzyme produces a strain or distortion of some of the chemical bonds that are found in the substrate moleculesC. Substrates are chemically changed into products D. Product is released E. The enzyme emerges from the reaction unchanged and ready to bind and change another molecule of substrate II. Enzyme classesA. Hydrolase- lactase catalyzes the hydrolysis of lactose B. Isomerase- triose phosphate isomeraseC. Ligase (polymerase)- DNA ligase can join two pieces of DNA that have complementary sticky ends D. Lyase- fructose- 1,6-biophosphate aldolaseE. Oxidoreductase- lactic acid dehydrogenase F. Transferase- pyruvate kinase transfers a phosphate from PEP to ADP II. Metabolic pathways and metabolic intermediates A. A metabolic pathway is a conceptual tool to help visualize relationships b/w some ofthe biochemical reactions that go in a cell. B. Many biosynthetic reactions (and biodegradations too) require 2 or more steps to get from the starting materials to the final products. When a biochemist write down the steps that a cell carries out to synthesize or degrade some compound, the resulting series of chemical reactions is called a metabolic pathway. There is no physical track in the cytoplasm that acts as a road for the movement of metabolic intermediates. C. A metabolic intermediate = a transitory product that is made from the starting material and is quickly converted to the next product. II. Simple proteins and conjugated proteins A. Simple protein- a chain of amino acidsB. conjugated enzyme consists of protein plus additional organic or inorganic molecules that are closely associated with the protein (ex. Succinate dehydrogenase-role is to remove 2 hydrogen atoms from succinate to produce