Microbial Metabolism Overview
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Questions and Answers

What are the two main categories of metabolic reactions?

  • Catabolism and Anabolism (correct)
  • Aerobic and Anaerobic
  • Autotrophy and Heterotrophy
  • Photosynthesis and Respiration

    • Anabolism is an energy-releasing process.

    False (B)

    What is the name given to reactions that involve the transfer of electrons?

    Redox reactions

    The ability of a substance to donate electrons during redox reactions is called its _____.

    <p>reducing power/potential</p> Signup and view all the answers

    Match the following terms to their correct definitions:

    <p>Catabolism = The breakdown of complex molecules to release energy Anabolism = The synthesis of complex molecules using energy Redox reactions = Reactions involving the transfer of electrons Reducing power/potential = The ability of a substance to donate electrons during electron transfer reactions</p> Signup and view all the answers

    Which of the following is NOT a requirement for microbial life?

    <p>Source of oxygen (C)</p> Signup and view all the answers

    Metabolism is a series of biochemical reactions necessary for the survival and growth of all living organisms, including microbes.

    <p>True (A)</p> Signup and view all the answers

    Describe the role of electron transfer reactions in metabolism.

    <p>Electron transfer reactions, or redox reactions, are central to metabolism as they drive energy production through the release of electrons from energy-rich molecules like glucose. These electrons are then transferred through a series of carriers, powering processes like ATP synthesis in both catabolism and anabolism.</p> Signup and view all the answers

    Which metabolic classification is given to organisms that obtain their electrons from organic molecules?

    <p>Chemoorganotrophs (B)</p> Signup and view all the answers

    Plants are considered chemoorganotrophs.

    <p>False (B)</p> Signup and view all the answers

    What is the reduction potential of the NAD+/NADH pair?

    <p>-0.32 V</p> Signup and view all the answers

    Organisms that obtain electrons from inorganic molecules are called _____ .

    <p>chemolithotrophs</p> Signup and view all the answers

    What happens to free energy as the difference in reduction potential between electron donor and acceptor increases?

    <p>It increases (B)</p> Signup and view all the answers

    Match the following terms with their respective definitions:

    <p>Chemoorganotrophs = Obtain energy from organic substrates Chemolithotrophs = Obtain electrons from inorganic substrates Autotrophs = Utilize carbon dioxide as a carbon source Heterotrophs = Obtain carbon from organic compounds</p> Signup and view all the answers

    The decomposition of organic compounds provides energy for heterotrophs.

    <p>True (A)</p> Signup and view all the answers

    What type of organisms use light for energy, inorganic substrates as electron sources, and CO2 as a carbon source?

    <p>Autotrophs</p> Signup and view all the answers

    What is the primary role of nitrogenase in nitrogen fixation?

    <p>Converts atmospheric nitrogen into ammonia (D)</p> Signup and view all the answers

    Oxygenic photosynthesis produces oxygen from the oxidation of carbon dioxide.

    <p>False (B)</p> Signup and view all the answers

    What key enzyme is involved in the Calvin cycle for fixing CO2?

    <p>Rubisco</p> Signup and view all the answers

    Anoxygenic photosynthesis involves only photosystem ____.

    <p>I</p> Signup and view all the answers

    Match the following terms to their definitions:

    <p>Enzyme that splits H2 = Hydrogenase Process converting N2 to NH3 = Nitrogen fixation Uses light energy to drive electron flow = Phototrophy Cycle that fixes CO2 = Calvin cycle</p> Signup and view all the answers

    Which organism specializes in nitrogen fixation and has a structure called heterocyst?

    <p>Cyanobacterium Anabaena (A)</p> Signup and view all the answers

    In nitrogen fixation, dinitrogenase reductase receives electrons directly from nitrogen gas.

    <p>False (B)</p> Signup and view all the answers

    What protects nitrogenase from O2 inactivation in Azotobacter vinelandii?

    <p>Slime</p> Signup and view all the answers

    What is produced as a result of fermentation by Clostridium butyricum?

    <p>Butyrate (B)</p> Signup and view all the answers

    Anaerobic conditions utilize oxygen as the terminal electron acceptor.

    <p>False (B)</p> Signup and view all the answers

    Name the process that involves chemical energy from redox reactions being conserved by pumping protons across a membrane.

    <p>Respiration</p> Signup and view all the answers

    In aerobic conditions, the terminal electron acceptor is _______.

    <p>Oxygen</p> Signup and view all the answers

    Match the following terms with their descriptions:

    <p>Aerobic Respiration = Uses oxygen as an electron acceptor Anaerobic Respiration = Uses alternative acceptors like nitrate Chemolithotrophy = Uses inorganic compounds as electron donors Fermentation = Produces energy in the absence of oxygen</p> Signup and view all the answers

    Which of the following is NOT a function of the proton gradient created during respiration?

    <p>Maintains membrane integrity (C)</p> Signup and view all the answers

    Chemotrophs primarily rely on photosynthesis for energy.

    <p>False (B)</p> Signup and view all the answers

    What are the two main types of electron donors used by organotrophs?

    <p>Glycolysis and fermentation</p> Signup and view all the answers

    What metabolic classification is given to an organism that requires light for energy and inorganic substrates as electron sources?

    <p>Photolithotrophs (B)</p> Signup and view all the answers

    Fermentation requires external electron acceptors for redox balance.

    <p>False (B)</p> Signup and view all the answers

    What is the net yield of the Citric Acid Cycle per molecule of Acetyl-CoA?

    <p>1 ATP, 4 NADH, 1 FADH2, 3 CO2</p> Signup and view all the answers

    The process where glucose is oxidized to pyruvate is known as ___.

    <p>glycolysis</p> Signup and view all the answers

    Match the following metabolic processes with their correct descriptions:

    <p>Glycolysis = Glucose oxidation to pyruvate Fermentation = Anaerobic catabolism without external acceptors Respiration = Catabolism with external electron acceptors Citric Acid Cycle = Conversion of Acetyl-CoA to CO2 and energy carriers</p> Signup and view all the answers

    What is produced in the NET YIELD of glycolysis?

    <p>2 ATP, 2 NADH, 2 Pyruvate (C)</p> Signup and view all the answers

    Chemoorganotrophs exclusively use inorganic molecules to fuel their metabolism.

    <p>False (B)</p> Signup and view all the answers

    In substrate-level phosphorylation, a phosphate group is transferred from a ____ substrate to ADP.

    <p>high-energy</p> Signup and view all the answers

    Flashcards

    Phototrophy

    The process by which light energy drives electron flow and generates proton motive force.

    Oxygenic Photosynthesis

    A process that produces oxygen from the oxidation of water; involves two photosystems.

    Anoxygenic Photosynthesis

    A type of photosynthesis that does not produce oxygen, utilizing only photosystem I.

    Calvin Cycle

    A series of reactions converting CO2 into organic compounds; requires Rubisco enzyme.

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    Nitrogen Fixation

    The process where certain bacteria convert atmospheric nitrogen (N2) into ammonia (NH3).

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    Nitrogenase

    An enzymatic complex that catalyzes nitrogen fixation; includes dinitrogenase and reductase.

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    Dinitrogenase Reductase

    Part of nitrogenase; receives electrons and transfers them to dinitrogenase using ATP.

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    Azotobacter vinelandii

    A bacterium that produces slime to protect itself from oxygen during nitrogen fixation.

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    Microbial Metabolism

    A series of biochemical reactions needed to sustain microbial life.

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    Metabolic Classification

    Categorization of microorganisms based on their metabolism.

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    Chemoorganotrophs

    Microorganisms that obtain energy by oxidizing organic compounds like glucose.

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    Fermentation

    A metabolic process that converts sugar to acids, gases, or alcohol in the absence of oxygen.

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    Catabolism

    Biochemical reactions that break down substrates to generate ATP.

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    Anabolism

    The synthesis of cellular materials from smaller units.

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    Redox Reactions

    Biochemical reactions involving the transfer of electrons between species.

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    Reducing Power

    The ability to donate electrons during redox reactions.

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    ATP production

    The process of generating adenosine triphosphate (ATP) from energetic substrates.

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    Butyric acid fermentation

    A process where butyric acid is produced by Clostridium butyricum, aiding gut health.

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    Respiration

    A process conserving chemical energy through redox reactions and electron transport.

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    Electron Transport Chain

    A series of complexes transferring electrons to create a proton gradient.

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    Proton Gradient

    An electrochemical gradient formed by pumping protons across a membrane during respiration.

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    Final Electron Acceptor

    Molecule that accepts electrons at the end of the electron transport chain.

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    Chemolithotrophy

    A metabolic process using inorganic compounds as electron donors.

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    Anaerobic Respiration

    A form of respiration using electron acceptors other than oxygen, like nitrate.

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    Electron transfer reactions

    Reactions involving the transfer of electrons between substances.

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    Strongest electron donors

    Substances that readily lose electrons during reactions, releasing energy.

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    Strongest electron acceptors

    Substances that readily gain electrons during reactions.

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    Reduction potential

    A measure of a substance’s tendency to gain electrons.

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    Heterotrophs

    Organisms that acquire carbon from organic sources.

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    Autotrophs

    Organisms that use CO2 as their carbon source.

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    Photolithotroph

    A type of autotroph that uses light for energy and inorganic compounds as electron sources.

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    Glycolysis

    The process of breaking down glucose into pyruvate, producing ATP and NADH.

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    Citric Acid Cycle

    A cyclical series of reactions converting Acetyl-CoA to CO2, yielding ATP and electron carriers.

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    ATP Yield in Glycolysis

    Net yield of glycolysis: 2 ATP, 2 NADH, and 2 pyruvate per glucose molecule.

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    Substrate-Level Phosphorylation

    Direct transfer of a phosphate group from a substrate to ADP to form ATP.

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    Study Notes

    Microbial Metabolism

    • Microbial metabolism is the series of biochemical reactions needed to sustain life.
    • These reactions include catabolism and anabolism.
    • Catabolism breaks down large molecules into smaller ones, releasing energy (exergonic).
    • Anabolism uses energy to build larger molecules from smaller ones (endergonic).
    • Key components for microbial life include water, a source of energy, a source of electrons, and a source of carbon.

    Metabolic Classifications of Microbes

    • Chemotrophs: Obtain energy from chemical reactions.

      • Organotrophs: Use organic molecules as electron sources.
        • Glycolysis (oxidizes glucose to pyruvate)
        • Fermentation (anaerobic process where organic compounds donate and accept electrons)
        • Respiration (aerobic and anaerobic processes, an electron donor is oxidized using an external electron acceptor)
      • Lithotrophs: Use inorganic molecules as electron sources.

    • Phototrophs: Obtain energy from light.

    • Autotrophs: Use carbon dioxide as their carbon source

    • Heterotrophs: Use organic compounds as their carbon source

    Electron Transport Reactions

    • Redox reactions (electron transfer) are critical for all life.
    • Electrons are transferred from a donor (reduced) to an acceptor (oxidized).
    • Reduction potential (E°) measures the tendency of a substance to gain electrons.
    • A larger difference in reduction potential between electron donor and acceptor = more free energy released

    The Redox Tower

    • The redox tower lists different redox couples in order of increasing reduction potentials.
    • Strongest electron donors are at the top of the negative end (more likely to lose electrons and be oxidized)
    • Strongest electron acceptors are at the bottom of the positive end (more likely to gain electrons and be reduced).
    • The larger the difference between each pair, the greater the energy released.

    Respiration

    • Aerobic respiration uses oxygen as a terminal electron acceptor.
    • Anaerobic respiration uses other components as terminal electron acceptors (nitrate, sulfate, or fumarate)
    • Electron transport chain (ETC) during respiration uses the energy released during electron transport to pump protons (ions) across a membrane. This creates an electrochemical gradient.
    • Protons flow through ATP synthase which produce ATP.
    • Different terminal electron acceptors result in various forms of anaerobic respiration, and different yields of ATP.

    Fermentation

    • Anaerobic catabolism in which organic compounds donate and accept electrons.
    • Redox balance achieved without external electron acceptors.
    • Substrate-level phosphorylation also occurs in fermentation, producing ATP from high-energy molecules.
    • Example: lactic acid fermentation, alcoholic fermentation

    Chemolithotrophy and Phototrophy

    • Chemolithotrophy: use inorganic compounds as a source of energy and electrons
    • Phototrophy: use light as energy source.
      • Oxygenic (water oxidzed, oxygen produced)
      • Anoxygenic (different electron donor, no oxygen produced).

    Nitrogen Fixation

    • Bacteria and Archaea perform nitrogen fixation: converting atmospheric nitrogen (N2) to ammonia (NH3).
    • The enzyme complex nitrogenase catalyzes this process, requiring ATP and special conditions to avoid oxygen inactivation of the enzyme.
    • Azotobacter vinelandii produces slime to protect cells from oxygen.

    Calvin Cycle

    • A series of biosynthetic reactions used by some photosynthetic and chemolithotrophic organisms to convert carbon dioxide (CO2) into organic compounds.
    • The key enzyme is Rubisco, which fixes CO2 to RuBP, forming an unstable 6-carbon molecule.
    • The resulting 3-phosphoglycerate molecules are then used for biosynthesis

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    L3 Microbial Metabolism PDF

    Description

    Explore the fascinating world of microbial metabolism, including catabolic and anabolic processes essential for microbial life. Understand key classifications of microbes such as chemotrophs and phototrophs, and their methods of obtaining energy from various sources.

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