lecture 8 Flashcards
microbial metabolism 3 (16 cards)
Distinguish among metabolism, anabolism, and catabolism.
Metabolism: All chemical reactions in a cell.
Anabolism: Building complex molecules (requires energy).
Catabolism: Breaking down molecules (releases energy).
Contrast oxidation and reduction reactions.
Oxidation: Loss of electrons (often releases energy).
Reduction: Gain of electrons (stores energy).
OIL RIG: Oxidation Is Loss, Reduction Is Gain (of electrons).
Compare and contrast the three types of ATP phosphorylation.
Substrate-level phosphorylation: Direct transfer of phosphate to ADP (Glycolysis, Krebs cycle)
Oxidative phosphorylation: Uses electron transport chain (ETC) to generate ATP (Aerobic respiration)
Photophosphorylation: Uses light energy to generate ATP (Photosynthesis)
Make a table listing the six basic types of enzymes, their activities, and an example of each.
Oxidoreductases: Transfer electrons (Lactate dehydrogenase)
Transferases: Transfer functional groups (Hexokinase)
Hydrolases: Break bonds using water (Lipase)
Lyases: Break bonds without water (Aldolase)
Isomerases: Rearrange atoms (Phosphoglucoisomerase)
Ligases: Join molecules using ATP (DNA ligase)
Define activation energy, enzyme, apoenzyme, cofactor, coenzyme, active site, and substrate, and describe their roles in enzyme activity.
Activation energy: Energy needed to start a reaction.
Enzyme: Biological catalyst that speeds up reactions.
Apoenzyme: Inactive protein part of an enzyme.
Cofactor: Non-protein helper (metal ions).
Coenzyme: Organic cofactor (NAD⁺, FAD).
Active site: Part of enzyme where substrate binds.
Substrate: The molecule an enzyme acts on.
Describe the components of a holoenzyme, and contrast protein and RNA enzymes.
Holoenzyme: Active enzyme = Apoenzyme (protein) + Cofactor (metal ion or coenzyme).
Protein enzymes: Made of amino acids, most enzymes are proteins.
RNA enzymes (Ribozymes): RNA molecules with catalytic activity (rRNA in ribosomes).
Describe how temperature, pH, substrate concentration, and competitive and noncompetitive inhibition affect enzyme activity.
Temperature: Too high denatures enzymes, too low slows reactions.
pH: Extreme pH disrupts enzyme shape.
Substrate concentration: More substrate increases reaction rate until saturation.
Competitive inhibition: Inhibitor binds active site, blocking substrate.
Noncompetitive inhibition: Inhibitor binds allosteric site, changing enzyme shape.
In general terms, describe the three stages of aerobic glucose catabolism (glycolysis, the Krebs cycle, and an electron transport chain), including their substrates, products, and net energy production.
Glycolysis: Glucose, 2 pyruvate, 2, NADH, 2 ATP (net)
Krebs Cycle: Acetyl-CoA, CO₂, NADH, FADH₂, 2 ATP
Electron Transport Chain (ETC): NADH, FADH₂, H₂O, ATP, ~34 ATP
Discuss the roles of acetyl-CoA, the Krebs cycle, and electron transport in carbohydrate catabolism.
Acetyl-CoA: Links glycolysis to the Krebs cycle.
Krebs Cycle: Produces electron carriers (NADH, FADH₂) for ETC.
ETC: Uses electrons to power ATP synthesis.
Contrast electron transport in aerobic and anaerobic respiration.
Aerobic respiration: Uses O₂ as the final electron acceptor (produces ~38 ATP).
Anaerobic respiration: Uses other molecules (e.g., nitrate, sulfate) as acceptors (fewer ATP).
Identify four classes of carriers in electron transport chains.
Flavoproteins (FAD, FMN)
Iron-sulfur proteins
Quinones (Coenzyme Q, Ubiquinone)
Cytochromes
Compare and contrast the ED and pentose phosphate pathway with EMP glycolysis in terms of energy production and products.
EMP Glycolysis: 2 ATP 2, pyruvate, NADH
Entner-Doudoroff (ED): 1 ATP, NADPH, pyruvate
Pentose Phosphate Pathway (PPP): Variable Ribose-5-phosphate (for nucleotides), NADPH
Describe several examples of the vast metabolic diversity in bacteria.
Sulfur bacteria: Use sulfur compounds for energy.
Methanogens: Produce methane in anaerobic conditions.
Phototrophic bacteria: Use light for energy.
Describe fermentation, and contrast it with respiration.
Fermentation: No ETC, produces little ATP, regenerates NAD⁺ (lactic acid fermentation).
Respiration: Uses ETC, produces much more ATP.
List three useful end-products of fermentation, and explain how fermentation reactions are used to identify bacteria.
Lactic acid (used in yogurt, cheese).
Ethanol (used in alcohol production).
Acetic acid (vinegar production).
Fermentation patterns help identify bacteria (Methyl Red test).
Discuss how biochemical tests for metabolic enzymes and products are used in the identification of bacteria.
Enzyme tests: Detect presence of metabolic enzymes (catalase test).
Sugar fermentation tests: Identify bacteria based on acid/gas production.
Urease test: Detects urease activity.
