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Microbiology Metabolism and Enzyme Function

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Terms in this set (30)

  • What is metabolism?

    Metabolism refers to all chemical reactions in organisms that break down substances to release energy and reactions that use energy to build new substances.

  • Name the three categories of metabolic pathways.

    1) Catabolic pathways: break down substances and release energy.
    2) Anabolic pathways: use energy to build new molecules.
    3) Amphibolic pathways: can function in both breakdown and synthesis.

  • What is the role of ATP in metabolism?

    ATP is made by catabolic reactions and provides energy for anabolic reactions; it is the key molecule cells use to do work.

  • What is an enzyme and what is its function?

    An enzyme is a protein catalyst that increases reaction rates by lowering activation energy without being consumed.

  • What is the active site of an enzyme?

    The active site is the region where the substrate binds and the enzyme catalyzes the reaction.

  • Explain the induced fit model of enzyme action.

    Enzymes and substrates are flexible; the enzyme molds around the substrate to position it properly for the reaction.

  • How do temperature and pH affect enzyme activity?

    Enzymes have optimal temperature and pH; extremes can denature enzymes, altering their shape and reducing activity.

  • What is enzyme denaturation?

    Denaturation is the loss of an enzyme's 3D structure due to heat or pH changes, causing loss of function.

  • What are cofactors and coenzymes?

    Cofactors are nonprotein components (like metal ions) needed for enzyme function; organic cofactors are called coenzymes.

  • What is feedback inhibition?

    A regulatory mechanism where the end product of a pathway inhibits an earlier enzyme to slow or stop the pathway.

  • Define redox reactions.

    Redox reactions involve oxidation (loss of electrons) and reduction (gain of electrons) occurring together.

  • What is the significance of NAD+ and FAD in metabolism?

    NAD+ and FAD are coenzymes that act as electron carriers in redox reactions, transporting electrons to the electron transport chain.

  • What are the three main stages of cellular respiration?

    1) Glycolysis
    2) Krebs cycle (citric acid cycle)
    3) Electron transport chain

  • What is substrate-level phosphorylation?

    Direct transfer of a phosphate group from a substrate to ADP to form ATP, occurring in glycolysis and Krebs cycle.

  • What is oxidative phosphorylation?

    ATP production using energy from a proton gradient generated by electron transport chains.

  • Where does glycolysis occur in cells?

    Glycolysis occurs in the cytoplasm (cytosol) of both prokaryotic and eukaryotic cells.

  • What are the end products of glycolysis per glucose molecule?

    2 pyruvate, 2 ATP (net), and 2 NADH molecules.

  • What happens during the intermediate step between glycolysis and Krebs cycle?

    Pyruvic acid undergoes decarboxylation to form acetyl-CoA, producing NADH and releasing CO₂.

  • What are the main products of the Krebs cycle per glucose?

    2 ATP (or GTP), 6 NADH, 2 FADH₂, and 4 CO₂ molecules.

  • What is chemiosmosis?

    The flow of protons down their gradient through ATP synthase, driving ATP production in the electron transport chain.

  • How many ATP molecules are produced per NADH and FADH₂ on average?

    Approximately 3 ATP per NADH and 2 ATP per FADH₂.

  • What is fermentation and its main purpose?

    Fermentation regenerates NAD⁺ by transferring electrons from NADH to organic molecules, allowing glycolysis to continue without oxygen.

  • Name two types of lactic acid fermentation.

    Homolactic fermentation (produces lactic acid only) and heterolactic fermentation (produces lactic acid, ethanol, and CO₂).

  • What enzymes break down lipids, proteins, and nucleic acids extracellularly?

    Lipases break down lipids, proteases break down proteins, and nucleases break down nucleic acids.

  • How are fatty acids catabolized for energy?

    Fatty acids undergo beta-oxidation to form acetyl-CoA, which enters the Krebs cycle.

  • What is gluconeogenesis?

    The anabolic process of synthesizing glucose from non-sugar precursors using intermediates from glycolysis and other pathways.

  • What distinguishes autotrophs from heterotrophs?

    Autotrophs fix inorganic carbon to make organic molecules; heterotrophs require external organic carbon sources.

  • What is the difference between phototrophs and chemotrophs?

    Phototrophs harvest energy from light; chemotrophs harvest energy from chemical bonds in nutrients.

  • What is the oxidase test used for?

    Detects the presence of cytochrome c oxidase enzyme in bacterial electron transport chains.

  • What does a positive catalase test indicate?

    Presence of catalase enzyme that breaks down hydrogen peroxide into water and oxygen, producing bubbles.