Enzymes

• Enzymes are protein catalysts that increase the rate of reactions without being changed in the overall process.
• Enzymes selectively channel reactants (called substrates) into useful pathways.
• Enzymes direct all metabolic events.
• Virtually all reactions in the body are mediated by enzymes.
• Enzymes are a Greek word, 'en' meaning 'in' and 'zyme' meaning 'yeast'.
• Enzymes are biologically used for diagnostic purposes.
• The key to corrections for Activity 3 includes identification of yeast, substrate, ribozyme, active site, and ESC or enzyme.
• The suggested videos for the lesson include an overview of enzymes, how enzymes work (energy of activation), factors affecting enzymatic activity, Michaelis - Menten Kinetics: Part 1, Michaelis - Menten and Lineweaver - Burk Plot: Part 2, and enzyme inhibition.
• The course code for the module is BIO 0 24.
• The student activity sheet is titled "Course Code: BIO 0 24 (Biochemistry/Biomolecules) Student Activity Sheet Module #4".
• The things that confuse students from the topic are not specified in the text.
• The document is the property of PHINMA EDUCATION.
• The lesson today is about Biochemistry/Biomolecules, specifically Module #4.
• In general, irreversible inhibitors bind to enzymes through covalent bonds.
• A numerically large (high) Km reflects a low affinity of enzyme for substrate, because a high concentration of substrate is needed to half-saturate the enzyme.
• A numerically small (low) Km reflects a high affinity of the enzyme for substrate, because a low concentration of substrate is needed to half-saturate the enzyme, reaching a velocity that is 1/2Vmax.
• When [S] is much less than Km, the velocity of the reaction is approximately proportional to the substrate concentration, and the rate of reaction is then said to be first order with respect to substrate.
• Any substance that can diminish the velocity of an enzyme-catalyzed reaction is called an inhibitor.
• Initial reaction velocities (vo) are used in the analysis of enzyme reactions.
• An intermediate in a series of reactions is said to be in steady state when its rate of synthesis is equal to its rate of degradation.
• Km is numerically equal to the substrate concentration at which the reaction velocity is equal to 1/2Vmax.
• Km, the Michaelis constant, is characteristic of an enzyme and its particular substrate, and reflects the affinity of the enzyme for that substrate.
• If the enzyme concentration is halved, the initial rate of the reaction (vo), as well as that of Vmax, are reduced to half that of the original.
• The Lineweaver - Burk plot can be used to calculate Km and Vmax, as well as to determine the mechanism of action of enzyme inhibitors.
• Km does not vary with the concentration of enzyme.
• When [S] is much greater than Km, the velocity is constant and equal to Vmax, and the rate of reaction is independent of substrate concentration, and is said to be zero order with respect to substrate concentration.
• The rate of the reaction is directly proportional to the enzyme concentration at all substrate concentrations.
• Virtually all chemical reactions have an energy barrier separating the reactants and the products.
• Coenzymes frequently are derived from vitamins (see vitamin module).
• An enzyme will catalyze only one reaction.
• Energy changes occurring during the reaction.
• For molecules to react, they must contain sufficient energy to overcome the energy barrier of the transition state.
• NAD+ contains niacin and FAD contains riboflavin.
• The rates of uncatalyzed chemical reactions are often slow due to the high (ΔG) free energy of activation.
• The enzyme will act on a particular type of chemical bond, irrespective of the rest of the molecular structure.
• The barrier, called the free energy of activation, is the energy difference between that of the reactants and a high-energy intermediate that occurs during the formation of product.
• Cosubstrates dissociate from the enzyme in an altered state (NAD+ is an example).
• This provides a favorable environment for the reaction, and organizes the thousands of enzymes present in the cell into purposeful pathways.
• Enzymes provide an alternate, energetically favorable reaction pathway different from the uncatalyzed reaction.
• Such compartmentalization serves to isolate the reaction substrate or product from other competing reactions.