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Microbiology Chapter 3

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Termini in questo insieme (89)

  • What is reducing power?

    The ability to donate electrons during electron-transfer (redox) reactions

  • What happens to an electron donor during a redox reaction?

    It donates electrons and is oxidized

  • What happens to an electron acceptor during a redox reaction?

    It accepts electrons and is reduced

  • What mnemonic describes oxidation and reduction?

    OIL RIG:

    Oxidation Is Loss of electrons

    Reduction Is Gain of electrons

  • What two half-reactions make up a redox reaction?

    One substance is oxidized and donates electrons, while another is reduced and accepts those electrons

  • What is catabolism?

    Reactions that break down complex molecules to obtain energy; they are exergonic

  • What is anabolism?

    Reactions that make cellular material; they are endergonic

  • How are catabolism and anabolism fundamentally linked?

    Catabolism produces ATP by breaking down molecules, while anabolism consumes ATP to biosynthesize cellular material

  • What is a chemotroph?

    An organism that obtains energy from chemical reactions

  • What is a phototroph?

    An organism that obtains energy from light

  • What is a chemolithotroph?

    An organism that obtains energy and reducing power from inorganic compounds, such as sulfur, nitrogen, or iron compounds

  • What is the main difference between a chemoorganotroph and chemolithotroph?

    Their source of energy and reducing power:

    Chemoorganotroph = organic compounds

    Chemolithotroph = inorganic compounds

  • What is an exergonic reaction?

    A reaction with negative ΔG°' that releases energy

  • What is an endergonic reaction?

    A reaction with positive ΔG°' that requires energy

  • Which type of reaction is generally associated with catabolism?

    Exergonic

  • Which type of reaction is generally associated with anabolism?

    Endergonic

  • What are three fundamental mechanisms cells use to generate ATP?

    Substrate-level phosphorylation, oxidative phosphorylation, and photophosphorylation

  • How does substrate-level phosphorylation generate ATP?

    An energy-rich substrate bond is hydrolyzed directly to drive ATP formation (cleaved to break bond which releases energy)

  • In what organisms is substrate-level phosphorylation especially important?

    It is the dominant energy-conservation mechanism in fermentative organisms

  • How does oxidative phosphorylation generate ATP?

    Movement of electrons generates a proton motive force (PMF) that is used to synthesize ATP

  • What organisms primarily use oxidative phosphorylation?

    Chemotrophic organisms during respiration

  • How does photophosphorylation generate ATP?

    Light is used to form a proton motive force that drives ATP synthesis

  • What organisms use photophosphorylation?

    Phototrophs

  • What do oxidative phosphorylation and photophosphorylation have in common?

    Both use the proton motive force to synthesize ATP

  • What is activation energy?

    The minimum energy required for a chemical reaction to begin

  • What is a catalyst?

    Something that facilitates a reaction without being consumed

  • How do enzymes affect activation energy?

    They lower activation energy, increasing the reaction rate

  • Where does a substrate bind to an enzyme?

    The active site

  • What is glycolysis?

    A nearly universal pathway for glucose catabolism that oxidizes glucose to pyruvate

  • What occurs during Stage I of glycolysis?

    It is the preparatory stage; energy is invested and the key intermediate glyceraldehyde-3-phosphate (G3P) is formed

  • How much ATP is consumed during Stage I of glycolysis?

    2 ATP

  • What occurs during Stage II of glycolysis?

    Redox reactions occur and energy is conserved, producing ATP, NADH, and pyruvate

  • How much ATP is produced during Stage II of glycolysis?

    4 ATP

  • What is the net yield of glycolysis per glucose?

    2 ATP + 2 NADH + 2 pyruvate

  • Why can't an organism grow using only glycolysis?

    Glycolysis lacks redox balance; NADH must be oxidized back to NAD+ so glycolysis can continue

  • How can NADH be recycled back to NAD+ after glycolysis?

    Through fermentation or coupling glycolysis to the citric acid cycle and respiration

  • What is the glyoxylate cycle used for?

    It allows some C2 compounds, such as acetate, to be catabolized and used to create CAC intermediates

  • What enzymes distinguish the glyoxylate cycle from the citric acid cycle?

    Isocitrate lyase and malate synthase

  • What important intermediates can the glyoxylate cycle produce?

    Succinate, oxaloacetate, and malate

  • What is the net yield of the CAC per glucose?

    8 NADH + 2 FADH2 + 2 ATP (or GTP) + 6 CO2

  • What is the combined yield of glycolysis + CAC per glucose?

    10 NADH + 2 FADH2 + 4 ATP + 6CO2

  • How does the citric acid cycle contribute to amino acid biosynthesis?

    α-ketoglutarate and oxaloacetate are precursors for several amino acids

  • What is succinyl-CoA used to synthesize?

    Cytochromes and chlorophyll

  • What is acetate needed for in biosynthesis?

    Fatty acid biosynthesis

  • What two metabolic results must every fermentation accomplish?

    Conserve energy and maintain redox balance

  • How does fermentation maintain redox balance?

    It oxidizes NADH back to NAD+ by donating electrons to an electron acceptor derived from the original organic donor

  • How does fermentation generate ATP?

    Through substrate-level phosphorylation

  • What are common fermentation waste products?

    Organic acids and alcohols

  • What are the major products of yeast fermentation of glucose?

    2 ethanol + 2 CO2, with ATP coming from glycolysis

  • What is the major product when lactic acid bacteria ferment glucose?

    2 lactic acid molecules

  • What is the total ATP yield per glucose from aerobic respiration?

    38 ATP: 2 from glycolysis, 2 from CAC, and 34 from electron transport

  • What major carbon product is released during complete aerobic respiration of glucose?

    6 CO2 per glucose

  • Why does aerobic respiration conserve much more energy than fermentation?

    Because in oxidative phosphorylation, the substrate is completely oxidized (34 ATP from oxidative phosphorylation vs 2 ATP from lactic acid fermentation)

  • What powers oxidative phosphorylation?

    Respiratory electrons

  • What powers photophosphorylation?

    Light energy

  • What do oxidative phosphorylation and photophosphorylation have in common?

    Both generate/use a proton motive force, which ATP synthase uses to make ATP

  • Can respiration occur with or without oxygen?

    Yes; respiration can occur under both oxic and anoxic conditions

  • What is aerobic respiration?

    Respiration that uses O2 as the terminal electron acceptor

  • What is anaerobic respiration?

    Respiration that uses a terminal electron acceptor other than O2

  • Does respiration use the proton motive force?

    Yes; electron transport creates a PMF that drives ATP synthesis through oxidative phosphorylation

  • Does fermentation use the proton motive force/electron transport to make ATP?

    No; fermentation generates ATP by substrate-level phosphorylation

  • Does phototrophy use the proton motive force?

    Yes; light generates the PMF, and ATP synthase produces ATP by photophosphorylation

  • What do chemoorganotrophs use as their energy and reducing power source?

    Organic compounds

  • What do chemolithotrophs use as electron donors?

    Inorganic chemicals (H2S, H2, FE2+, NH4+)

  • What is a heterotroph?

    An organism that obtains carbon from organic compounds

  • What is an autotroph?

    An organism that obtains carbon from CO2

  • What are nearly all chemoorganotrophs in terms of carbon source?

    Heterotrophs

  • What are most chemolithotrophs and phototrophs in terms of carbon source?

    Autotrophs

  • Why must atmospheric CO2 and N2 be chemically reduced?

    So their carbon and nitrogen can be assimilated for biosynthesis

  • What two things are required to reduce atmospheric carbon and nitrogen for assimilation?

    ATP and reducing power

  • What is CO2 fixation?

    Chemical reduction of atmospheric CO2 for assimilation into cellular material

  • What is nitrogen fixation?

    Conversion of gaseous N2 into ammonia (NH3)

  • What enzyme complex carries out nitrogen fixation?

    Nitrogenase

  • Why does nitrogenase need protection?

    Nitrogenase is inhibited by oxygen

  • What are two ways nitrogen-fixing organisms protect nitrogenase from oxygen?

    Slime layers and heterocysts (which create an anoxic environment)

  • What is gluconeogenesis?

    Synthesis of glucose from phosphoenolpyruvate

  • What are pentose sugars used for?

    They are required for the synthesis of nucleic acids

  • What major pathway produces pentoses and NADPH?

    The pentose phosphate pathway

  • What important reducing power molecule is generated by the pentose phosphate pathway?

    NADPH, which is used in DNA and fatty acid biosynthesis

  • What activated glucose molecule is a precursor for structural polysaccharides?

    Uridine diphosphoglucose (UDPG)

  • What is an amino acid family?

    A group of amino acids that share common biosynthetic steps

  • What pathways provide the carbon skeletons used for amino acid biosynthesis?

    Glycolysis and the citric acid cycle

  • How are lipids assembled in Bacteria and Eukarya?

    By adding fatty acids to glycerol

  • How are archaeal lipids different?

    Archaea make their lipids from isoprene, rather than the fatty acids used by Bacteria and Eukarya

  • What type of lipid tails are characteristic of Bacteria?

    Linear fatty acid tails

  • What type of lipid tails are characteristic of Archaea?

    Long branched isoprenoid tails

  • What bonds attach bacterial fatty acid tails to glycerol?

    Ester bonds

  • What bonds attach archaeal isoprenoid tails to glycerol?

    Ether bonds

  • What unusual membrane arrangement can certain heat-loving Archaea form?

    A lipid monolayer instead of a bilayer