Deck 3: Microbial Metabolism

Question 1

A chemoorganotroph and a chemolithotroph in the same environment would NOT compete for

A) oxygen.
B) carbon.
C) nitrogen.
D) phosphorous.

Answer 1

B

Question 2

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 2

A

Question 3

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 3

C

Question 4

Activation energy is the energy

A) required to transform all reactants into their reactive state.
B) given off as the products in a chemical reaction are formed.
C) absorbed as ΔG⁰' moves from negative to positive.
D) needed by an enzyme to catalyze a reaction without coenzymes.

Question 5

What is the difference between a coenzyme and a prosthetic group?

A) Coenzymes are essential for an enzyme's 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.

Question 6

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.

Question 7

All microorganisms require

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

Question 8

The class of macromolecules in microorganisms that contributes MOST to biomass is

A) carbohydrates.
B) DNA.
C) lipids.
D) proteins.

Question 9

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.

Question 10

Which of the following would be used by a chemoorganotroph for energy?

A) C₂H₃O₂⁻
B) H₂
C) CO₂
D) H⁺

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.

Question 12

Which is an example of a micronutrient?

A) arginine
B) inorganic phosphorous
C) iron
D) vitamin B₁₂

Question 13

Based on the functional roles of phosphate in various microbial metabolisms,deduce which compounds phosphate exists as in microorganisms.

A) organic compounds
B) inorganic compounds
C) both organic and inorganic compounds
D) neither organic nor inorganic compounds

Question 14

A chemoorganotroph and a photoautotroph in the same environment would NOT compete for

A) oxygen.
B) carbon.
C) nitrogen.
D) carbon and oxygen.

Question 15

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

Question 16

Based on your understanding of metabolism,generalize when an enzyme's 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

Question 17

The sum of all biosynthetic reactions in a cell is known as

A) metabolism.
B) anabolism.
C) catabolism.
D) synthatabolism.

Question 18

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.

Question 19

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

Question 20

If ΔG⁰' 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.

Question 21

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.

Question 22

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

Question 23

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

Question 24

All of the following are non-protein electron carriers EXCEPT

A) FADH₂.
B) FMNH₂.
C) cytochromes.
D) quinones.

Question 25

In aerobic respiration,the final electron acceptor is

A) hydrogen.
B) oxygen.
C) water.
D) ATP.

Question 26

Which intermediate compound(s)in the citric acid cycle is/are often used for biosynthetic pathways as well as carbon catabolism?

A) α-ketoglutarate
B) oxaloacetate
C) succinyl-CoA
D) α-ketoglutarate, oxaloacetate, and succinyl-CoA

Question 27

The net gain of ATP per molecule of glucose fermented is

A) 1.
B) 2.
C) 4.
D) 8.

Question 28

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.

Question 29

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.

Question 30

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.

Question 31

The Embden-Meyerhof-Parnas pathway is another name for

A) the citric acid cycle.
B) glycolysis.
C) electron transport.
D) NADH production.

Question 32

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.

Question 33

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.

Question 34

Which feature of anaerobic and aerobic respiration is different between the two catabolic strategies?

A) electron donor
B) electron acceptor
C) use of electron transport
D) use of proton motive force

Question 35

From the standpoint of the microorganism,in glycolysis the crucial product is

A) ATP; 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.

Question 36

One example of an electron acceptor that can be used in anaerobic respiration is

A) NADH.
B) water.
C) nitrate.
D) FMN.

Question 37

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.

Question 38

Which of the following is a common energy storage polymer in microorganisms?

A) acetyl~S-CoA
B) glycogen
C) adenosine triphosphate
D) H₂

Question 39

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.

Question 40

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.

Question 41

The proton motive force is most often generated by splitting of H₂.

Question 42

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.

Question 43

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

Question 44

Free-energy calculations are dependent on the rates of the reactions.

Question 45

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.

Question 46

Which metabolic strategy does NOT invoke the proton motive force for energy conservation?

A) aerobic catabolism
B) anaerobic
C) chemoorganotrophy
D) photoautrophy

Question 47

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.

Question 48

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

Question 49

If a substance is reduced,it gains electrons.

Question 50

Regeneration of oxaloacetate is essential for the citric acid cycle to be cyclical.

Question 51

Nitrogenases not only reduce N₂ but also can act on acetylene (C₂H₂).

Question 52

Molebdenum is a cofactor for nitrogenase,which means every nitrogen-fixing microorganisms will not be able to fix nitrogen without Mo.

Question 53

Biosynthesis of glucose can occur by compounds other than sugars via gluconeogenesis.

Question 54

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

Question 55

Magnesium is not considered a growth factor for microorganisms,because growth factors are always organic compounds.

Question 56

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.

Question 57

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

Question 58

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.

Question 59

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

Question 60

Hypothetically,if electron pools 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.

Question 61

Explain what an enzyme must accomplish to catalyze a specific reaction.

Question 62

Varied coenzyme availability increases the diversity of enzymatic reactions in both biosynthetic and catabolic pathways possible in a cell.

Question 63

Differentiate between exergonic and endergonic in terms of free-energy calculations.

Question 64

Many defined growth media that support microbial growth lack malonate,which is an important precursor for biosynthesis of lipid membranes.Based on this,we can infer cells also must have a metabolic pathway to generate malonate from other compounds.

Question 65

A bacterium that lacks an arginine biosynthetic pathway would still be able to make proteins with arginine and grow only if arginine is supplemented into the growth medium.

Question 66

In an aquatic microbial community where a photoautotroph,chemoorganoheterotroph,and nitrogen fixing bacterium are present,predict an environmental perturbation that would cause only one to be outcompeted by the other two groups and explain how each group would respond.

Question 67

Discuss why energy yield in an organism undergoing anaerobic respiration is less than that of an organism undergoing aerobic respiration.

Question 68

Explain the biosynthetic and bioenergetic roles of the citric acid cycle.

Question 69

Compare and contrast defined media and complex media.Use specific examples in your answer.

Question 70

In substrate-level phosphorylation,ATP storage is depleted during the steps in catabolism of the fermentable compounds.

Question 71

Cells require iron supplemented in their growth medium as a trace metal,because it is consumed by quinones during electron transport for ATP production.

Question 72

Heme prosthetic groups are involved in electron transfer with quinones.

Question 73

Contrast fermentation and respiration in terms of electron donor,electron acceptor,type of ATP production,and relative number of ATP produced.

Question 74

Catabolic pathways are essential for microorganisms to obtain energy,because biosynthetic reactions for cellular growth generally require energy input.

Question 75

Summarize the roles the proton motive force has in microbial metabolism.

Question 76

During the electron transport process,protons and electrons become physically separated in the cell membrane.

Question 77

The energy released from the hydrolysis of coenzyme A is conserved in the synthesis of ATP.

Question 78

The net result of electron transport is the generation of a pH gradient and an electrochemical potential across the membrane.

Question 79

Categorize the circumstances under which the same substance (molecule)can be either an electron donor or an electron acceptor.

Question 80

In electron transport systems,the electron carriers are membrane associated.