C3 Brock Sample Questions

Question 1

The prokaryotic transport system that involves a substrate-binding protein, a membrane-integrated transporter, and an ATP-hydrolyzing protein is
A) the ABC transport system.
B) group translocation.
C) symport.
D) simple transport.

Answer 1

A) the ABC transport system.

ABC (ATP-Binding Cassette) transport systems are characterized by their use of ATP hydrolysis to transport substrates across cell membranes, often involving substrate-binding proteins and membrane-integrated transporters.

Question 2

The sum of all biosynthetic reactions in a cell is known as
A) metabolism.
B) anabolism.
C) catabolism.
D) synthatabolism.

Answer 2

B) anabolism.

Anabolism refers to the set of metabolic pathways that construct molecules from smaller units, requiring energy. This contrasts with catabolism, which breaks down molecules to release energy.

Question 3

Based on the functional roles of phosphate in various microbial metabolisms, which of the following compounds most likely contain phosphate?
A) organic compounds
B) inorganic compounds
C) both organic and inorganic compounds
D) neither organic nor inorganic compounds

Answer 3

C) both organic and inorganic compounds

Phosphate groups are crucial in both organic (e.g., nucleic acids, phospholipids, ATP) and inorganic (e.g., phosphate ions) compounds within microbial metabolisms.

Question 4

Which of the following would be used by a chemoorganotroph for energy?
A) C2H3O2-
B) H2
C) CO2
D) H+

Answer 4

A) C2H3O2-

Chemoorganotrophs derive energy from the oxidation of organic compounds. C2H3O2- could represent an organic acid, a plausible energy source.

Question 5

Which of the following statements is FALSE?
A) Most bacteria are capable of using ammonia as their sole nitrogen source.
B) Some bacteria are able to use nitrates or nitrogen gas as their nitrogen source.
C) Most available nitrogen is in organic forms.
D) Nitrogen is a major component of proteins and nucleic acids.

Answer 5

C) Most available nitrogen is in organic forms.

While significant, most of the Earth’s nitrogen is in inorganic form (N2 in the atmosphere), not organic forms, making this statement false.

Question 6

All microorganisms require
A) carbon, iron, and sodium.
B) phosphorus, aluminum, and sodium.
C) calcium, potassium, and magnesium.
D) phosphorus, selenium, and sulfur.

Answer 6

D) phosphorus, selenium, and sulfur.

All microorganisms require phosphorus (for nucleic acids, ATP, etc.), selenium (as a trace element for some enzymes), and sulfur (for amino acids and some vitamins).

Question 7

Which element functions BOTH as an enzyme cofactor and as a stabilizer of ribosomes and nucleic acids?
A) iron
B) hydrogen
C) zinc
D) magnesium

Answer 7

D) magnesium

Magnesium ions (Mg2+) serve as cofactors for many enzymes and also play a crucial role in stabilizing ribosomes and the structure of nucleic acids.

Question 8

Based on your understanding of metabolism, generalize when an enzymeʹs rate of activity can be changed.
A) before enzyme production
B) during enzyme production
C) after enzyme production
D) at any point—before, during, or after enzyme production

Answer 8

D) at any point—before, during, or after enzyme production

Enzyme activity can be influenced at various stages: before production (genetic regulation), during (allosteric modulation, substrate availability), and after (post-translational modifications, degradation).

Question 9

The change in Gibbs free energy for a particular reaction is most useful in determining
A) the amount of energy catalysts required for biosynthesis or catabolism.
B) the potential metabolic reaction rate.
C) whether there will be a requirement or production of energy.
D) energy stored in each compound.

Answer 9

C) whether there will be a requirement or production of energy.

ΔG indicates the spontaneity of a reaction; a negative ΔG suggests energy release (exergonic), while a positive ΔG indicates energy requirement (endergonic).

Question 10

Which is an example of a micronutrient?
A) arginine
B) inorganic phosphorous
C) iron
D) vitamin B12

Answer 10

C) iron

Iron is a micronutrient (trace element) essential for various microbial enzymes and processes, including electron transport chains.

Question 11

Aseptic technique refers to
A) the microbial inoculum placed into a test tube or onto a Petri plate.
B) a series of practices to avoid contamination.
C) the autoclave and other sterilizing procedures.
D) cleanliness in the laboratory.

Answer 11

B) a series of practices to avoid contamination.

Aseptic techniques are methods used to prevent the introduction of microorganisms into a culture, thereby maintaining sterility.

Question 12

To ensure growth of a newly discovered bacterium with unknown nutritional requirements, it would be best to begin with a _______ medium rather than a _________ medium.
A) complex / minimal
B) minimal / complex
C) selective / complex
D) selective / differential

Answer 12

A) complex / minimal

Complex media provide a broad spectrum of nutrients, increasing the chances of supporting the growth of a bacterium with unknown nutritional needs, as opposed to minimal media which contain only the essential nutrients.

Question 13

If ΔG0ʹ is negative, the reaction is
A) exergonic and requires the input of energy.
B) endergonic and requires the input of energy.
C) exergonic and energy will be released.
D) endergonic and energy will be released.

Answer 13

C) exergonic and energy will be released.

A negative ΔG0ʹ indicates that the reaction is spontaneous under standard conditions, releasing energy (exergonic).

Question 14

Activation energy is the energy
A) required for a chemical reaction to begin.
B) given off as the products in a chemical reaction are formed.
C) absorbed as ΔG0ʹ moves from negative to positive.
D) needed by an enzyme to catalyze a reaction without coenzymes.

Answer 14

A) required for a chemical reaction to begin.

Activation energy is the minimum amount of energy that must be provided for compounds to result in a chemical reaction.

Question 15

A catalyst
A) requires more reactants but makes the reaction rate faster.
B) increases the amount of reactants produced but does not change the rate.
C) changes the rate of the reaction but does not change the end amount of products.
D) changes both the rate of a reaction and the amount of the product that will be obtained as the reaction is completed.

Answer 15

C) changes the rate of the reaction but does not change the end amount of products.

Catalysts, like enzymes, speed up reactions without altering the reaction’s equilibrium or the amount of product formed.

Question 16

The portion of an enzyme to which substrates bind is referred to as the
A) substrate complex.
B) active site.
C) catalytic site.
D) junction of van der Waals forces.

Answer 16

B) active site.

The active site is the specific region of an enzyme where substrate molecules bind, allowing the enzyme to catalyze the reaction.

Question 17

What is the difference between a coenzyme and a prosthetic group?
A) Coenzymes are essential for an enzymeʹs function and prosthetic groups only enhance its reaction rate.
B) Coenzymes are weakly bound whereas prosthetic groups are strongly bound to their respective enzymes.
C) Coenzymes are organic cofactors and prosthetic groups are inorganic cofactors.
D) Coenzymes require additional ions to bind to enzymes but prosthetic groups are able to directly interact with enzymes.

Answer 17

B) Coenzymes are weakly bound whereas prosthetic groups are strongly bound to their respective enzymes.

Coenzymes are organic, non-protein molecules that bind loosely to enzymes and can be released during the catalytic process. Prosthetic groups are tightly bound to enzymes, often through covalent bonds.

Question 18

If an oxidation reaction occurs
A) simultaneous reduction of a different compound will also occur, because electrons do not generally exist alone in solution.
B) another oxidation reaction will occur for a complete reaction, because one oxidation event is considered a half reaction.
C) a cell is undergoing aerobic respiration, because oxygen is being used.
D) a reduction reaction would not occur, because they are opposite reaction mechanisms.

Answer 18

A) simultaneous reduction of a different compound will also occur, because electrons do not generally exist alone in solution.

Oxidation and reduction are coupled reactions (redox reactions); when one compound is oxidized, another must be reduced to accept the electrons.

Question 19

The class of macromolecules in microorganisms that contributes most to biomass is
A) carbohydrates.
B) DNA.
C) lipids.
D) proteins.

Answer 19

D) proteins.

Proteins are the most abundant class of macromolecules in most microbial cells, contributing significantly to cellular biomass.

Question 20

A chemoorganotroph and a chemolithotroph in the same environment would NOT compete for
A) oxygen.
B) carbon.
C) nitrogen.
D) phosphorous.

Answer 20

B) carbon.

Chemoorganotrophs derive energy from organic compounds, while chemolithotrophs derive energy from inorganic compounds. Thus, they wouldn’t compete for carbon sources in the context of energy acquisition.

Question 21

A chemoorganotroph and a photoautotroph in the same environment would NOT compete for
A) oxygen.
B) carbon.
C) nitrogen.
D) carbon and oxygen.

Answer 21

A) oxygen.

Photoautotrophs (like plants and cyanobacteria) produce oxygen through photosynthesis, while chemoorganotrophs consume oxygen for respiration. Thus, they have an opposite relationship with oxygen.

Question 22

The Embden-Meyerhof-Parnas pathway is another name for
A) the citric acid cycle.
B) glycolysis.
C) electron transport.
D) NADH production.

Answer 22

B) glycolysis.

The Embden-Meyerhof-Parnas (EMP) pathway is indeed another name for glycolysis, a metabolic pathway that converts glucose into pyruvate, releasing energy.

Question 23

The net gain of ATP per molecule of glucose fermented is
A) 1.
B) 2.
C) 4.
D) 8.

Answer 23

B) 2.

In the process of fermentation, the net gain of ATP per glucose molecule is typically 2 ATP, as the process bypasses the ATP-yielding steps of the citric acid cycle and oxidative phosphorylation.

Question 24

Which of the following is a common energy storage polymer in microorganisms?
A) acetyl-S-CoA
B) glycogen
C) adenosine triphosphate
D) H2

Answer 24

B) glycogen

Glycogen serves as a form of energy storage in many microorganisms, analogous to starch in plants and glycogen in animals.

Question 25

Fermentation has a relatively low ATP yield compared to aerobic respiration because
A) more reducing equivalents are used for anaerobic catabolism.
B) less ATP is consumed during the first stage of aerobic catabolism.
C) oxidative phosphorylation yields a lot of ATP.
D) substrate-level phosphorylation yields a lot of ATP.

Answer 25

C) oxidative phosphorylation yields a lot of ATP.

The primary reason fermentation yields less ATP than aerobic respiration is that the latter utilizes oxidative phosphorylation, a highly efficient ATP-producing process.

Question 26

From the standpoint of fermentative microorganisms, the crucial product in glycolysis is
A) ATP and regenerated NAD+; the fermentation products are waste products.
B) ethanol or lactate; ATP is a waste product.
C) CO2; ATP is a waste product.
D) not relevant because glycolysis is not a major pathway.

Answer 26

A) ATP and regenerated NAD+; the fermentation products are waste products.

For fermentative microorganisms, the key outcomes of glycolysis are the net gain of ATP and the regeneration of NAD+, allowing the process to continue. Fermentation products are essentially waste.

Question 27

In aerobic respiration, the final electron acceptor is
A) hydrogen.
B) oxygen.
C) water.
D) ATP.

Answer 27

B) oxygen.

In aerobic respiration, oxygen (O2) serves as the terminal electron acceptor of the electron transport chain.

Question 28

Which of the following is NOT membrane-associated?
A) NADH dehydrogenases
B) flavoproteins
C) cytochromes
D) Cytochromes, flavoproteins, and NADH dehydrogenases all can be membrane-associated.

Answer 28

D) Cytochromes, flavoproteins, and NADH dehydrogenases all can be membrane-associated.

All listed components are indeed associated with membranes, particularly in the context of electron transport chains.

Question 29

During electron transport reactions
A) OH- accumulates on the outside of the membrane while H+ accumulates on the inside.
B) OH- accumulates on the inside of the membrane while H+ accumulates on the outside.
C) both OH- and H+ accumulate on the inside of the membrane.
D) both OH- and H+ accumulate on the outside of the membrane.

Answer 29

B) OH- accumulates on the inside of the membrane while H+ accumulates on the outside.

In electron transport, protons (H+) are pumped out of the cell across the membrane, creating a proton gradient. Hydroxide ions (OH-) can accumulate inside due to the consumption of H+ ions, but the primary focus is on the H+ gradient.

Question 30

The rising of bread dough is the result of
A) biotin production.
B) carbon dioxide produced by fermentation.
C) oxidative phosphorylation.
D) oxygen being released.

Answer 30

B) carbon dioxide produced by fermentation.

Yeast fermentation produces CO2 as a byproduct, which gets trapped in the dough, causing it to rise.

Question 31

Which intermediate compound(s) in the citric acid cycle is/are often used for biosynthetic pathways as well as carbon catabolism?
A) only α-ketoglutarate
B) only oxaloacetate
C) only succinyl-CoA
D) α-ketoglutarate, oxaloacetate, and succinyl-CoA

Answer 31

D) α-ketoglutarate, oxaloacetate, and succinyl-CoA.

These intermediates can be diverted for biosynthesis: α-ketoglutarate for amino acid synthesis, oxaloacetate for gluconeogenesis, and succinyl-CoA for porphyrin and heme synthesis.

Question 32

Microbial growth on the two-carbon acetate substrate invokes
A) the citric acid cycle for aerobic catabolism.
B) both the citric acid and glyoxylate pathways.
C) the glyoxylate pathway.
D) the glyoxylate and glycolysis pathways.

Answer 32

C) the glyoxylate pathway.

The glyoxylate pathway is specifically used for the metabolism of two-carbon compounds like acetate, allowing for growth on these substrates.

Question 33

Which is one major difference between anaerobic and aerobic respiration?
A) electron donor
B) electron acceptor
C) use of electron transport
D) use of proton motive force

Answer 33

B) electron acceptor.

The primary difference lies in the electron acceptor used: oxygen (O2) in aerobic respiration versus other compounds (e.g., nitrate, sulfate) in anaerobic respiration.

Question 34

For a carbon source, chemoorganotrophs generally use compounds such as
A) acetate, succinate, and glucose.
B) bicarbonate and carbon dioxide.
C) nitrate and nitrite.
D) acetate, bicarbonate, and nitrate.

Answer 34

A) acetate, succinate, and glucose.

Chemoorganotrophs derive energy from organic compounds, which can include simple acids (acetate, succinate) and sugars (glucose).

Question 35

All of the following are non-protein electron carriers EXCEPT
A) FADH2.
B) FMNH2.
C) cytochromes.
D) quinones.

Answer 35

C) cytochromes.

Cytochromes are indeed non-protein electron carriers when considering the broader definition of “non-protein.” However, in a strict sense, cytochromes are proteins with a prosthetic heme group.

Question 36

Which two metabolic processes are most dissimilar?
A) citric acid cycle and glycolysis
B) glycolysis and gluconeogenesis
C) proton motive force and substrate-level phosphorylation
D) pentose phosphate pathway and glycolysis

Answer 36

C) proton motive force and substrate-level phosphorylation.

These processes generate ATP through fundamentally different mechanisms: proton motive force utilizes a transmembrane proton gradient, while substrate-level phosphorylation involves direct ATP synthesis during metabolic pathway reactions.

Question 37

How does the proton motive force lead to production of ATP?
A) ATPase requires one proton to make one ATP.
B) Protons must be pumped against a concentration gradient from outside of the cell into the cell to rotate the F0 subunit of ATPase for the F1 subunit to make ATP.
C) Oxidative phosphorylation of ADP by ATP synthase requires protons as cofactors in the reaction.
D) Translocation of three to four protons drives the F0 component of ATPase which in turn phosphorylates one ADP into ATP.

Answer 37

D) Translocation of three to four protons drives the F0 component of ATPase which in turn phosphorylates one ADP into ATP.

The flow of protons back across the membrane through ATP synthase drives the production of ATP from ADP and Pi.

Question 38

Five-carbon sugars are used in the
A) biosynthesis of DNA and RNA.
B) catabolic pentose phosphate pathway for carbon and energy.
C) biosynthesis of DNA and RNA as well as catabolic pentose phosphate pathway.
D) activation of pentoses to form glycogen for energy storage.

Answer 38

C) biosynthesis of DNA and RNA as well as catabolic pentose phosphate pathway.

Pentoses (5-carbon sugars) are crucial for nucleic acid biosynthesis (DNA and RNA) and are also metabolized through the pentose phosphate pathway for energy and biosynthetic precursors.

Question 39

Improperly functioning acyl carrier proteins (ACPs) would likely result in
A) a physiological shift to anaerobic metabolism where an energized membrane is less important for energy production.
B) enhanced growth of a bacterium due to faster growth substrate uptake by a weakened membrane.
C) no harm to bacteria, because only archaeons and eukaryotes use ACPs for fatty acid biosynthesis.
D) death for a bacterium due to poor lipid bilayer integrity.

Answer 39

D) death for a bacterium due to poor lipid bilayer integrity.

ACPs are crucial for fatty acid biosynthesis, which is essential for membrane lipid production. Dysfunction could lead to compromised membrane integrity, potentially lethal for the bacterium.

Question 40

A bacterium running low on NADPH could ________ to generate more of this coenzyme.
A) degrade an amino acid or nucleic acid
B) invoke the pentose phosphate pathway
C) degrade a fatty acid
D) use a broad specificity phosphatase with inorganic phosphatase and NADH

Answer 40

B) invoking the pentose phosphate pathway.

The pentose phosphate pathway is a significant source of NADPH in cells, crucial for biosynthetic reactions and maintaining the redox balance.

Question 41

One example of an electron acceptor that can be used in anaerobic respiration is
A) NADH.
B) water.
C) nitrate.
D) FMN.

Answer 41

C) nitrate.

In the absence of oxygen, certain microorganisms can use nitrate (NO3-) as an alternative electron acceptor for anaerobic respiration.

Question 42

When culturing a chemoorganoheterophic bacterium, what outcome is LEAST likely to occur if ammonia and phosphate are provided at equal concentrations?
A) Cells require much less P to grow than N, so extra P will be used for ATP synthesis and result in a faster growth rate.
B) Cells will never consume all of the phosphate, because N is needed in higher quantities than P.
C) The final biomass of cells will be no different than if only 50% of the phosphate was provided.
D) The bacteria will import all of the ammonia to use for biosynthetic pathways.

Answer 42

D) The bacteria will import all of the ammonia to use for biosynthetic pathways.

The statement is too absolute; bacteria will use ammonia for biosynthesis but will not necessarily import all of it, as the need also depends on the availability of other nutrients and the bacterium’s growth phase.

Question 43

Most of the carbon in amino acid biosynthesis comes from
A) citric acid cycle intermediates.
B) citric acid cycle intermediates and glycolysis products.
C) glycolysis products.
D) glycolysis intermediates and products.

Answer 43

B) citric acid cycle intermediates and glycolysis products.

Both sources provide crucial precursors for amino acid biosynthesis: citric acid cycle intermediates (e.g., α-ketoglutarate for glutamate) and glycolysis products (e.g., pyruvate for alanine).

Question 44

Which metabolic cycle or pathway is LEAST likely to be invoked during the biosynthesis of DNA?
A) citric acid cycle
B) glycolysis
C) gluconeogenesis
D) pentose phosphate pathway

Answer 44

A) citric acid cycle.

The citric acid cycle is primarily catabolic, generating energy and reducing equivalents. While some of its intermediates can be diverted for biosynthesis, it’s less directly involved in DNA biosynthesis compared to pathways like the pentose phosphate pathway.

Question 45

Hypothetically, if free electrons existed in sufficient numbers for enzymes to use in metabolic reactions
A) a higher diversity of cytochromes would likely be observed.
B) cytochromes would be unnecessary for cells and quinones would be more important.
C) Q-cycle reactions would no longer be necessary for electron transport, but the proton motive force would otherwise be unchanged.
D) most metabolic pathways for both anabolism and catabolism would have to be rewritten.

Answer 45

D) most metabolic pathways for both anabolism and catabolism would have to be rewritten.

The availability of free electrons would fundamentally alter the energetic and thermodynamic considerations of metabolic pathways, necessitating a reevaluation of how energy is harvested and utilized in cells.

Question 46

Which metabolic strategy does NOT invoke the proton motive force for energy conservation?
A) aerobic catabolism
B) fermentation
C) chemoorganotrophy
D) photoautrophy

Answer 46

B) fermentation.

Fermentation generates energy through substrate-level phosphorylation without the establishment of a proton gradient across a membrane, unlike respiration which relies on the proton motive force for ATP synthesis.

Question 47

T/F: ATP-binding cassette transport systems have high substrate affinity and thus help microorganisms survive in low nutrient environments.

Answer 47

TRUE

These systems are known for their high affinity for substrates, aiding survival in low-nutrient conditions.

Question 48

T/F: A bacterial isolate that grows better on a nutrient agar plate supplemented with amino acids but still grows in a nutrient agar plate lacking amino acids suggests amino acids are trace nutrients for the isolate.

Answer 48

FALSE

This scenario indicates the bacterium can synthesize its own amino acids but grows better with supplementation, suggesting amino acids are not just trace nutrients.

Question 49

T/F: Regeneration of oxaloacetate is essential for the citric acid cycle to be cyclical.

Answer 49

TRUE

Oxaloacetate regeneration is crucial for the citric acid cycle to continue as a cyclic process.

Question 50

T/F: Depending on the particular metabolism of a bacterium, electron transport can be used to energize and rotate ATP synthase.

Answer 50

TRUE

In various bacterial metabolisms, electron transport is utilized to generate a proton motive force, driving ATP synthase.

Question 51

T/F: Each amino acid made during protein biosynthesis first requires a separate biosynthetic pathway to be invoked by a cell.

Answer 51

FALSE

While many amino acids have dedicated pathways, some can be synthesized through shared or interconnected pathways.

Question 52

T/F: The terminating step of moving electrons onto oxygen releases additional ATP during aerobic metabolism not made during anaerobic growth.

Answer 52

TRUE

Oxygen as a terminal electron acceptor in aerobic respiration yields more ATP compared to anaerobic processes.

Question 53

T/F: Nitrogenases not only reduce N2 but also can act on acetylene (C2H2).

Answer 53

TRUE

Nitrogenase enzymes are known to reduce both nitrogen gas (N2) and acetylene (C2H2), the latter being a diagnostic feature.

Question 54

T/F: Due to the number of phosphate groups, ATP has approximately three times more energy stored than AMP, and ADP has approximately two-thirds the energy stored of ATP.

Answer 54

FALSE

The energy difference is not directly proportional to the number of phosphate groups in this simplistic manner.

Question 55

T/F: In a given chemical reaction, if the free energy of formation is known for all of the reactants and each of the products, the change in free energy can be calculated for the reaction.

Answer 55

TRUE

Knowing the free energy of formation for all reactants and products allows for the calculation of the reaction’s overall change in free energy.

Question 56

T/F: Free-energy calculations are dependent on the rates of the reactions.

Answer 56

FALSE

Free-energy calculations provide information on the thermodynamic feasibility of a reaction, not its rate.

Question 57

T/F: With respect to nitrogen utilization, relatively few bacteria can use NH3 whereas many more can make use of N2.

Answer 57

FALSE

In reality, many bacteria can use NH3, and relatively few have the capability to fix N2.

Question 58

T/F: The proton motive force is most often generated by splitting of H2.

Answer 58

FALSE

The proton motive force is primarily generated through electron transport chains, not the direct splitting of H2.

Question 59

T/F: Biosynthesis of glucose can occur by compounds other than sugars via gluconeogenesis.

Answer 59

TRUE

Gluconeogenesis is a metabolic pathway that synthesizes glucose from non-carbohydrate sources.

Question 60

T/F: If a substance is reduced, it gains electrons.

Answer 60

TRUE

Reduction involves the gain of electrons by a substance.

Question 61

T/F: Molybdenum is a cofactor for nitrogenase, which means every nitrogen-fixing microorganism will not be able to fix nitrogen without Mo.

Answer 61

FALSE

While molybdenum is a cofactor for some nitrogenases, alternative nitrogenases use different metals (e.g., vanadium, iron-only), allowing nitrogen fixation without molybdenum.