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Quizzes > Science

Microbiology Chapter 8: Metabolism and Enzymes Quiz

Quick quiz to test your understanding of cellular respiration basics. Instant results.

Editorial: Review CompletedCreated By: Soul SamaUpdated Aug 23, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art microbes test tubes and molecule icons on dark blue background promoting chapter 8 microbial metabolism quiz

Use this quiz to check your understanding of Microbiology Chapter 8: metabolism and enzymes, from ATP and catabolism to how enzymes are controlled. Build vocabulary with the enzyme vocabulary quiz and practice steps with enzyme practice problems. For wider review, try a microbiology exam practice quiz to see how these pathways link across the course.

What term describes the sum of all chemical reactions in a microbial cell?
Respiration
Homeostasis
Reproduction
Metabolism
Metabolism includes all the chemical reactions that occur in a cell, encompassing both catabolic and anabolic processes. This term covers energy generation, biosynthesis, and breakdown of molecules. No other term accurately describes the totality of these reactions. See for more details.
Which term describes the energy-releasing breakdown of complex molecules in microbes?
Anabolism
Homeostasis
Catabolism
Biosynthesis
Catabolism refers to the set of metabolic pathways that break down complex molecules into simpler ones, releasing energy stored in chemical bonds. This energy is then often captured in the form of ATP. Anabolism is the opposite process, building complex molecules. For more information, see .
Which molecule is the primary energy currency in microbial cells?
NADH
GTP
ATP
FADH2
ATP (adenosine triphosphate) stores and transfers energy for many cellular processes in microbes and all living cells. Hydrolysis of its high-energy phosphate bonds provides the energy needed for biosynthesis, transport, and motility. While NADH and FADH2 carry electrons, they are not the universal energy currency. Learn more at .
What part of an enzyme binds to its substrate?
Allosteric site
Cofactor binding site
Regulatory site
Active site
The active site is a specific region on an enzyme where the substrate binds and the chemical reaction occurs. Its unique 3D structure is complementary to the substrate, ensuring specificity. Allosteric sites, in contrast, bind regulatory molecules that modulate enzyme activity. For further details, see .
Which term describes an organic nonprotein molecule that assists enzyme function?
Zymogen
Prosthetic group
Coenzyme
Apoenzyme
Coenzymes are organic nonprotein molecules that bind temporarily or permanently to enzymes to assist in catalysis by carrying chemical groups or electrons. Apoenzymes are the protein component of an enzyme without its cofactor. Zymogens are inactive enzyme precursors. For more, visit .
When a molecule competes with a substrate for an enzyme's active site, this is called what?
Allosteric regulation
Feedback activation
Competitive inhibition
Noncompetitive inhibition
Competitive inhibition occurs when an inhibitor closely resembles the substrate and binds to the active site, blocking substrate entry. This type of inhibition can be overcome by increasing substrate concentration. Noncompetitive inhibitors bind elsewhere and change the enzyme's shape. For more details, see .
A reaction where a molecule gains electrons is called what?
Reduction
Oxidation
Phosphorylation
Hydrolysis
Reduction refers to the gain of electrons by a molecule, often accompanied by the gain of hydrogen. Oxidation is the loss of electrons. In microbial metabolism, redox reactions are fundamental for energy transfer. Learn more at .
What is the end product of glycolysis under anaerobic conditions in many bacteria?
Lactate
Pyruvate
Ethanol
Acetyl-CoA
Glycolysis converts glucose into two molecules of pyruvate, producing ATP and NADH in the process. Under anaerobic conditions, pyruvate is further processed via fermentation but is the direct end product of glycolysis itself. Lactate and ethanol are products of subsequent fermentation pathways. See .
In metabolism, NAD+ functions primarily as what?
Structural component
Energy currency
Electron carrier
Carbon source
NAD+ (nicotinamide adenine dinucleotide) is a coenzyme that accepts electrons during oxidation reactions, becoming NADH. It shuttles electrons to the electron transport chain or fermentation pathways. It is not directly an energy currency like ATP. See for more.
Which enzyme catalyzes the rate-limiting step of glycolysis?
Aldolase
Pyruvate kinase
Phosphofructokinase
Hexokinase
Phosphofructokinase-1 (PFK-1) catalyzes the irreversible conversion of fructose-6-phosphate to fructose-1,6-bisphosphate and is the key rate-limiting step in glycolysis. Its activity is tightly regulated by ATP, ADP, and other metabolites. Hexokinase initiates glycolysis but is not rate-limiting. More information at .
How many molecules of NADH are produced per acetyl-CoA during the citric acid cycle?
4
1
3
2
Each turn of the citric acid cycle oxidizes one acetyl-CoA, producing three NADH, one FADH2, and one GTP (or ATP). The NADH molecules carry electrons to the electron transport chain for ATP generation. The other options underrepresent or overestimate the yield. Refer to .
Where is the electron transport chain located in prokaryotic cells?
Periplasmic space
Mitochondrial inner membrane
Cell wall
Cytoplasmic membrane
In bacteria and archaea, the electron transport chain is embedded in the cytoplasmic (plasma) membrane, enabling proton translocation across it. Prokaryotes lack mitochondria, so they use their cell membrane for respiration. The periplasmic space and cell wall do not house the full chain of complexes. See .
Which two components comprise the proton motive force across a membrane?
Electrical potential and pH gradient
Sodium gradient and electrical potential
ATP concentration and pH gradient
Temperature difference and pressure difference
The proton motive force consists of a membrane potential (electrical potential) and a pH gradient (chemical potential) across the membrane. These two components store energy used by ATP synthase to generate ATP. ATP concentration is a result, not a component, and sodium or temperature differences refer to other gradients. For more, see .
Which process directly synthesizes ATP by transferring a phosphate group from a substrate to ADP?
Substrate-level phosphorylation
Oxidative phosphorylation
Photophosphorylation
Chemiosmotic phosphorylation
Substrate-level phosphorylation occurs when a high-energy phosphate group is transferred directly from an intermediate metabolite to ADP, forming ATP. This contrasts with oxidative phosphorylation, which uses a proton gradient. Photophosphorylation happens in photosynthetic membranes. See .
What is the primary purpose of fermentation in microbes?
To produce maximum ATP
To reduce FAD
To synthesize pyruvate
To regenerate NAD+ for glycolysis
Fermentation pathways regenerate NAD+ by transferring electrons from NADH back to pyruvate or its derivatives. This allows glycolysis to continue producing ATP under anaerobic conditions. Fermentation does not yield additional NADH or high ATP yields like respiration. Learn more at .
Which microorganism is known for mixed acid fermentation producing acetic, lactic, succinic, and formic acids?
Escherichia coli
Bacillus subtilis
Lactobacillus bulgaricus
Saccharomyces cerevisiae
Escherichia coli can perform mixed acid fermentation, producing a variety of acids including acetic, lactic, succinic, and formic acids under anaerobic conditions. Lactobacillus primarily produces lactic acid, while Saccharomyces cerevisiae uses alcohol fermentation. Bacillus subtilis is capable of different metabolic processes. See .
In anaerobic respiration, which molecule can serve as a terminal electron acceptor instead of oxygen?
NAD+
Water
Nitrate (NO3 - )
Glucose
In anaerobic respiration, molecules like nitrate, sulfate, or fumarate can serve as terminal electron acceptors instead of oxygen. Nitrate (NO3 - ) is commonly reduced to nitrite in many bacteria. Glucose is a substrate, not an electron acceptor, and NAD+ is a carrier. For details, see .
What is the primary goal of beta-oxidation in fatty acid metabolism?
To produce glycerol
To synthesize fatty acids
To release ammonia
To generate acetyl-CoA units
Beta-oxidation is the stepwise removal of two-carbon acetyl-CoA units from fatty acids, which can then enter the citric acid cycle for energy production. It does not synthesize fatty acids; that is the function of fatty acid synthesis pathways. Glycerol metabolism and ammonia release are unrelated. More at .
What does a low Km value indicate about an enzyme's affinity for its substrate?
Low affinity
High turnover number
High affinity
Strong competitive inhibition
Km represents the substrate concentration at which the reaction rate is half of Vmax. A low Km indicates that the enzyme reaches half-maximal activity at a low substrate concentration, meaning it has high affinity for the substrate. Km does not directly describe turnover number or inhibition strength. For more, see .
Which molecule acts as a feedback inhibitor for citrate synthase in the TCA cycle?
Acetyl-CoA
NADH
ADP
NAD+
NADH accumulates when the electron transport chain slows, signaling that energy levels are high. NADH binds to citrate synthase, inhibiting its activity and slowing the citric acid cycle. NAD+ and ADP generally act as activators in energy-limited states. See .
What is the main function of the glyoxylate shunt in bacteria?
To convert acetyl-CoA into four-carbon compounds without CO2 loss
To oxidize fatty acids
To ferment sugars
To generate ATP directly
The glyoxylate shunt bypasses the decarboxylation steps of the TCA cycle, allowing organisms to convert acetyl-CoA into succinate and other four-carbon compounds without releasing CO2. This is critical when microbes grow on C2 substrates like acetate. It does not produce ATP directly. More information at .
Which metabolic pathway generates NADPH and pentose sugars critical for biosynthesis in microbes?
Citric acid cycle
Pentose phosphate pathway
Glycolysis
Beta-oxidation
The pentose phosphate pathway produces NADPH, used in reductive biosynthesis, and ribose-5-phosphate for nucleotide synthesis. Glycolysis primarily yields ATP and NADH. The citric acid cycle and beta-oxidation serve energy production roles. For more, see .
In bacterial electron transport chains, which complex pumps protons using electrons from NADH?
Complex III (cytochrome bc1)
Complex I (NADH dehydrogenase)
Complex IV (cytochrome c oxidase)
Complex II (succinate dehydrogenase)
Complex I (NADH dehydrogenase) oxidizes NADH to NAD+, transfers electrons to ubiquinone, and pumps protons across the membrane. Complex II does not pump protons, while complexes III and IV handle later electron transfers. For more details, see .
Who proposed the chemiosmotic theory of ATP synthesis?
James Watson
Louis Pasteur
Peter Mitchell
Frederick Griffith
Peter Mitchell proposed the chemiosmotic theory in 1961, suggesting that a transmembrane proton gradient drives ATP synthesis in mitochondria and bacteria. This theory revolutionized understanding of oxidative phosphorylation. Other scientists named did not develop this concept. See .
What term describes the direct passage of an intermediate between enzymes without diffusion into the bulk solvent?
Substrate channeling
Active transport
Coenzyme transfer
Facilitated diffusion
Substrate channeling involves the transfer of an intermediate metabolite directly from one enzyme's active site to the next enzyme in a pathway. This increases the efficiency and protects unstable intermediates. It differs from membrane transport processes. For more, see .
Which prosthetic group in Complex I of the electron transport chain initially accepts electrons from NADH?
Iron-sulfur cluster
FMN
Heme
FAD
In Complex I (NADH dehydrogenase), flavin mononucleotide (FMN) is the first prosthetic group to accept two electrons from NADH, forming FMNH2. These electrons are then transferred through iron - sulfur clusters. FAD is not used in Complex I. More at .
Which cofactor is essential for pyruvate dehydrogenase complex activity?
Thiamine pyrophosphate (TPP)
Biotin
Pyridoxal phosphate
Coenzyme Q
The pyruvate dehydrogenase complex requires thiamine pyrophosphate (TPP) as a cofactor for the decarboxylation of pyruvate. Biotin is used in carboxylation reactions, and pyridoxal phosphate in amino acid metabolism. Coenzyme Q shuttles electrons in the ETC. See .
Which equation relates the standard free energy change (?G°') of a redox reaction to the difference in standard reduction potentials (?E°')?
?G°' = R T ?E°'
?G°' = -nF?E°'
?G°' = -RT ln K
?G°' = nF?E°'
The relationship ?G°' = -nF?E°' describes how the standard free energy change of an electron transfer reaction depends on the number of electrons transferred (n), Faraday's constant (F), and the difference in standard reduction potentials (?E°'). This equation is fundamental in bioenergetics. The other equations describe different thermodynamic relationships. See .
Which metabolite is the most potent allosteric inhibitor of bacterial phosphofructokinase?
Citrate
ADP
ATP
Phosphoenolpyruvate (PEP)
In many bacteria, phosphoenolpyruvate (PEP) feedback inhibits phosphofructokinase to regulate glycolytic flux. PEP accumulation signals bottlenecks downstream in glycolysis, decreasing further flow through the pathway. ATP and citrate also inhibit PFK but are less potent in bacterial systems. See .
During the rotational catalysis mechanism of ATP synthase in E. coli, how many ATP molecules are synthesized per full 360° rotation of the gamma subunit?
3
12
1
9
In E. coli ATP synthase, the gamma subunit rotates 360° per three protons translocated and synthesizes three ATP molecules, corresponding to the three catalytic sites on the F1 region. Each 120° step produces one ATP. This rotational catalysis was detailed by the .
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Study Outcomes

  1. Understand Core Metabolic Pathways -

    Grasp the key steps and intermediates in major microbial pathways, including glycolysis, the Krebs cycle, and fermentation, as covered in quizlet chapter 8 microbiology.

  2. Differentiate Anabolic and Catabolic Reactions -

    Distinguish between energy-consuming biosynthetic reactions and energy-releasing degradative processes in microbial metabolism.

  3. Analyze Enzyme Kinetics -

    Interpret how factors like temperature, pH, and substrate concentration influence enzyme activity in microbial systems.

  4. Identify Key Enzymes and Coenzymes -

    Recognize the roles of critical enzymes and coenzymes that drive energy production and metabolic regulation in chapter 8 microbiology.

  5. Apply Metabolic Principles -

    Use knowledge from quizlet microbiology chapter 8 to predict microbial growth and energy yield under different environmental conditions.

  6. Evaluate Regulation Mechanisms -

    Assess how microbes control metabolic flux through feedback inhibition and gene regulation to maintain homeostasis.

Cheat Sheet

  1. Anabolic vs Catabolic Reactions -

    Chapter 8 microbiology emphasizes that anabolic pathways consume ATP to synthesize macromolecules, while catabolic reactions release energy by breaking down substrates. Remember "Anabolic Adds, Catabolic Cuts" as a quick mnemonic (Campbell Biology, 2020).

  2. Enzyme Kinetics and Michaelis - Menten -

    In quizlet chapter 8 microbiology, the Michaelis - Menten equation v = Vmax [S]/(Km + [S]) describes how enzyme velocity depends on substrate concentration. Visualizing a Lineweaver - Burk plot can help you linearize data for easier Km and Vmax determination (Berg et al., 2002).

  3. Glycolysis Pathway and Energy Yield -

    Quizlet microbiology chapter 8 notes glycolysis converts glucose to two pyruvate molecules, yielding a net 2 ATP and 2 NADH per glucose (Voet & Voet, 2011). An easy way to remember is "Investment of 2 ATP, return of 4 ATP" for a net gain of 2 ATP.

  4. Tricarboxylic Acid (TCA) Cycle Essentials -

    Chapter 8 microbiology outlines that each acetyl-CoA entering the TCA cycle produces 3 NADH, 1 FADH2, and 1 GTP (Lehninger Principles of Biochemistry, 2017). Use the acronym "Citrate Is Krebs' Starting Substrate For Making Oxaloacetate" to memorize cycle intermediates.

  5. Electron Transport Chain & Chemiosmosis -

    Quizlet chapter 8 microbiology highlights how the ETC establishes a proton motive force across the membrane, driving ATP synthesis via ATP synthase (Peter Mitchell, Nobel Prize theory). A typical P/O ratio of ~3 for NADH helps estimate ATP yield during oxidative phosphorylation.

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