Exam #2: Mastering Microbiology

Question 1

A defined culture medium is designed to meet the needs of a particular type of organism, suppling all of the nutrients the organism needs, including essential biochemicals that the cell cannot synthesize. Based on the following recipe, this defined medium would best support the growth of certain members of what group?

Recipe: 7 g of K2HPO4; 2 g of KH2PO4; 1g of (NH4)2SO4; 0.1g of MgSO4; 0.02g of CaCl2; 10g of glucose; trace elements mix; 1000 mL of distilled water; adjust to pH 7.

A. chemolithotroph

B. chemoorganotroph

C. phototroph

D. autotroph

Answer 1

B. chemoorganotroph

Question 2

Which statement below demonstrates why the majority of organisms are heterotrophs?

A. The majority of organisms obtain their carbon from organic sources.

B. The majority of organisms conserve energy from inorganic sources.

C. The majority of organisms obtain their carbon from inorganic sources.

D. The majority of organisms conserve energy from inorganic sources and their carbon from organic sources.

Answer 2

A.The majority of organisms obtain their carbon from organic sources.

Question 3

In metabolism, energy that is not used

A. is stored in the form of ATP.

B. is given off as heat.

C. is used to break down large molecules into smaller ones.

D. is used to build up large compounds from smaller ones.

Answer 3

B. is given off as heat.

Question 4

The reactions involved in producing larger compounds from smaller compounds is called

A. catabolism.

B. metabolism.

C. anabolism

Answer 4

C. anabolism

Question 5

Where does the energy required for anabolic reactions come from?

A. Catabolic reactions

B. Heat

C. Unused energy from metabolism

Answer 5

A. Catabolic reactions

Question 6

The use of amino acids to make proteins

A. involves the production of ATP.

B. is an example of anabolism.

C. is an example of catabolism.

D. is a completely efficient reaction.

Answer 6

B. is an example of anabolism.

Question 7

Lipases break down

A. lipids.

B. proteins.

C. nucleic acids.

D. carbohydrates.

Answer 7

A. lipids.

Question 8

The Pentose Phosphate Pathway

A. is a part of photosynthesis.

B. is another name for fermentation.

C. is an example of anabolism.

D. is an example of catabolism.

Answer 8

C. is an example of anabolism.

Question 9

According to the animation, oxidative phosphorylation

A. is a catabolic process.

B. makes larger compounds from smaller ones.

C. requires a net input of energy.

D. is an anabolic process.

Answer 9

A. is a catabolic process.

Question 10

According to the animation, the reactions that occur between glucose and pyruvic acid

A. can either be anabolic or catabolic.

B. are only catabolic.

C. are only anabolic.

D. are neither catabolic nor anabolic.

Answer 10

A. can either be anabolic or catabolic.

Question 11

Part complete

To calculate the free energy (ΔG⁰′) of a reaction, you can subtract the free energies of formation (Gf⁰) of the reactants from those of the products. Given the following data, what will be true of this reaction? C₆H₁₂O₆ + O₂ → CO₂ + H₂O Gf⁰ : -917.3 0 -394.4 -237.2

A. The reaction will be exergonic.

B. The reaction will not require a catalyst to proceed.

C. The reaction will be endergonic.

D. The reaction is not balanced, so you cannot calculate the change in free energy

Answer 11

A. The reaction will be exergonic.

Question 12

The role of an enzyme includes all EXCEPT which of the following?

A. lowering the activation energy of a reaction

B. reducing the rate of a reaction to allow for better control

C. straining chemical bonds in a substrate so that they break easier

D. binding only one specific substrate to the enzyme active site

Answer 12

B. reducing the rate of a reaction to allow for better control

Question 13

Why do all enzymatic reactions need activation energy?

A. Energy is required to disrupt a substrate’s stable electron configuration.

B. Energy is needed for the enzyme to find its substrate.

C. Energy allows only the substrate to bind.

D. Energy is required by an enzyme so that it can be reused.

Answer 13

A. Energy is required to disrupt a substrate’s stable electron configuration.

Question 14

What is meant by the statement “Enzymes are biological catalysts”?

A. Enzymes are products of biological systems.

B. Enzymes speed up the chemical reactions in living cells.

C. Enzymes produce products useful for biology.

D. Enzymes produce biological organisms.

Answer 14

B. Enzymes speed up the chemical reactions in living cells.

Question 15

Why are enzymes important to biological systems?

A. Enzymes increase the energy barrier required of chemical reactions

B. Enzymes decrease the amount of activation energy required for chemical reactions to occur.

C. Enzymes are reuseable.

D. Enzymes prevent unwanted chemical by-products from forming.

Answer 15

B. Enzymes decrease the amount of activation energy required for chemical reactions to occur.

Question 16

The reduction potential (E₀′) of a substance reflects its tendency to donate or accept electrons. The larger the difference (ΔE₀′) between the reduction potentials of the electron donor and the electron acceptor, __________.

A. the more enzymes will be required to catalyze the reaction(s)

B. the greater the change in free energy (ΔG₀′), and the greater the energy released

C. the greater the change in free energy (ΔG₀′), and the less energy is released

D. the closer the substances are on the electron tower

Answer 16

B. the greater the change in free energy (ΔG₀′), and the greater the energy released

Question 17

The function of NAD+/NADH in the cell is best described as __________.

A. a way to increase the types of redox reactions that occur in the cell by acting as an intermediary between dissimilar compounds

B. a way to transport electrons to the mitochondria for energy generation in bacteria

C. a way to transport protons to the plasma membrane for energy generation in bacteria

D. a way to increase the types of redox reactions that occur in the cell by acting as an intermediary between similar compounds

Answer 17

A. a way to increase the types of redox reactions that occur in the cell by acting as an intermediary between dissimilar compounds

Question 18

A reaction that involves the transfer of electrons from one molecule to another is referred to as

A. a reduction reaction.

B. an oxidation reaction.

C. a redox reaction.

Answer 18

C. a redox reaction.

Question 19

During an oxidation reaction,

A. the donor molecule loses an electron and becomes oxidized.

B. the donor molecule gains an electron and becomes oxidized.

C. the acceptor molecule gains an electron and becomes oxidized.

D. the acceptor molecule loses an electron and becomes oxidized.

Answer 19

A. the donor molecule loses an electron and becomes oxidized.

Question 20

Why is reduction the term used to describe the gain of an electron?

A. The number of molecules in the reaction decreases.

B. The amount of energy in the molecule decreases

C. The electron acceptor’s net charge decreases.

D. The electron acceptor gets smaller.

Answer 20

C. The electron acceptor’s net charge decreases.

Question 21

Part complete

Which of the following statements regarding redox reactions is true?

A. No metabolic reactions are redox reactions.

B. Redox reactions involve an oxidation reaction coupled with a reduction reaction.

C. Redox reactions are only seen in the electron transport chain.

D. Redox reactions must either be oxidizing reactions or reducing reactions.

Answer 21

B. Redox reactions involve an oxidation reaction coupled with a reduction reaction.

Question 22

Which of the following would NOT be required to grow an autotroph?

A. water

B. potassium phosphate

C. glucose

D. trace elements

Answer 22

C. glucose

Question 23

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

A. CO₂

B. H+

C. C₂H₃O₂-

D. H₂

Answer 23

C. C₂H₃O₂-

Question 24

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

A. oxygen.

B. carbon.

C. phosphorous.

D. nitrogen.

Answer 24

B. carbon.

Question 25

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

A. nitrogen.

B. oxygen.

C. carbon.

D. carbon and oxygen.

Answer 25

D. carbon and oxygen.

Question 26

For a carbon source, chemoorganotrophs generally use compounds such as

A. bicarbonate and carbon dioxide.

B. acetate, bicarbonate, and nitrate

C. nitrate and nitrite.

D. acetate, succinate, and glucose.

Answer 26

D. acetate, succinate, and glucose.

Question 27

The change in Gibbs free energy for a particular reaction is most useful in determining

A. the potential metabolic reaction rate.

B. energy stored in each compound.

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

D. the amount of energy catalysts required for biosynthesis or catabolism.

Answer 27

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

Question 28

If ΔG0 is negative, the reaction is

A. exergonic and requires the input of energy.

B. exergonic and energy will be released.

C. endergonic and energy will be released.

D. endergonic and requires the input of energy.

Answer 28

B. exergonic and energy will be released.

Question 29

The portion of an enzyme to which substrates bind is referred to as the

A. junction of van der Waals forces.

B. catalytic site

C. substrate complex.

D. active site.

Answer 29

D. active site.

Question 30

Activation energy is the energy

A. required for a chemical reaction to begin.

B. absorbed as ΔG0 moves from negative to positive.

C. needed by an enzyme to catalyze a reaction without coenzymes.

D. given off as the products in a chemical reaction are formed.

Answer 30

A. required for a chemical reaction to begin.

Question 31

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 31

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

Question 32

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.

A. True

B. False

Answer 32

B. False

Question 33

From the standpoint of fermentative microorganisms, the crucial product in glycolysis is

A. CO₂; ATP is a waste product.

B. ethanol or lactate; ATP is a waste product.

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

D. not relevant because glycolysis is not a major pathway.

Answer 33

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

Question 34

Applying your knowledge of metabolism, glycolysis starts with one molecule of glucose (6C) and produces a net total of __________.

A. one pyruvate; 2 NADH; 2 ATP

B. two pyruvates; 4 NADH; 2 ATP

C. one pyruvate; 2 NADH; 4 ATP

D. two pyruvates; 2 NADH; 2 ATP

Answer 34

D. two pyruvates; 2 NADH; 2 ATP

Question 35

Why is ATP required for glycolysis?

A. ATP is used to convert PEP into pyruvic acid.

B. ATP makes it easier to break apart glucose into two three-carbon molecules.

C. ATP is used to convert DHAP into G3P.

D. ATP is used to reduce NAD+ to NADH.

Answer 35

B. ATP makes it easier to break apart glucose into two three-carbon molecules.

Question 36

Glycolysis literally means

A. Embden-Meyerhof.

B. energy producing.

C. sugar producing.

D. sugar splitting.

Answer 36

D. sugar splitting.

Question 37

How many net ATPs can be made from one molecule of glucose in glycolysis?

A. One

B. Two

C. Six

D. Four

Answer 37

B. Two

Question 38

What carbon molecules remain at the end of glycolysis?

A. Pyruvic acid

B. Glucose

C. Glyceraldehyde 3-phosphate (G3P)

D. Dihydroxyacetone phosphate (DHAP)

Answer 38

A. Pyruvic acid

Question 39

Which of the following statements about glycolysis is true?

A. Glycolysis produces glucose.

B. Glycolysis is also called the Embden-Meyerhof pathway.

C. Glycolysis is the main source of NADH in the cell.

D. All cells perform glycolysis.

Answer 39

B. Glycolysis is also called the Embden-Meyerhof pathway.

Question 40

Glycolysis produces energy in which form?

A. Pyruvic acid

B. NADH

C. NADH, ATP, and pyruvic acid

D. ATP

E. NADH and ATP

Answer 40

E. NADH and ATP

Question 41

Which step is the step for which glycolysis is named?

A. First

B. Second

C. Third

D. Fourth

E. Fifth

F. Sixth

Answer 41

D. Fourth

Question 42

What is meant by substrate-level phosphorylation?

A. Reduction of NAD+ to NADH

B. Production of ATP using energy from a proton gradient

C. Production of ATP by transferring phosphates directly from metabolic products to ADP

D. Splitting of glucose into two pyruvic acid molecules

Answer 42

C. Production of ATP by transferring phosphates directly from metabolic products to ADP

Question 43

What is the driving force of energy production in steps 6 and 7?

A. The oxidation of three-carbon compounds

B. The reduction of NAD+ to NADH

C. The energy potential of a proton gradient

D. The reduction of three-carbon compounds

Answer 43

A. The oxidation of three-carbon compounds

Question 44

What is the net production of ATP in glycolysis?

A. Six ATP

B. Four ATP

C. Two ATP

D. Eight ATP

Answer 44

C. Two ATP

Question 45

Correctly identify steps occurring in this typical electron transport chain diagram.

• Q- cycle reactions
• Electrons enter the chain from a primary electron donor
• Electrons exit the chain by reducing the terminal electron acceptor (O₂)
• When FMH₂ reduces an Fe/S protein (an electron-only carrier) protons are extruded

Answer 45

Question 46

Electron carriers used in electron transport chains are always found in membranes. Which one of the following statements is NOT a reason why electron transport chains are found in membranes?

A. so that they can transport NADH out of the cell to the periplasm

B. so that the electron carriers can be oriented within the membrane such that protons are passed from one side of the membrane to the other

C. So that electron-only carriers can be arranged to alternate with electron-plus-proton carriers in the chain.

D. so that they can efficiently pass electrons in sequence from the carriers with the more negative reduction potentials to those with the more positive reduction potentials

Answer 46

A. so that they can transport NADH out of the cell to the periplasm

Question 47

The proton motive force (PMF) is driven by __________.

A. the pumping of protons through the plasma membrane

B. the difference in charge across the plasma membrane with electrons outside the membrane

C. the difference in charge across the plasma membrane with protons outside the membrane

D. the pumping of electrons though the plasma membrane

Answer 47

C. the difference in charge across the plasma membrane with protons outside the membrane

Question 48

Where would you expect to find electron transport chains in a prokaryote?

A. Along the plasma membrane

B. Along the cell wall

C. Free-floating in the cytoplasm

D. Along the inner mitochondrial membrane

E. Along the outer mitochondrial membrane

Answer 48

A. Along the plasma membrane

Question 49

According to the animation, which compounds provide electrons to the system?

A. FADH₂

B. NADH and FADH₂

C. NADH

D. Water

E. Oxygen

Answer 49

B. NADH and FADH₂

Question 50

According to the animation, what does oxygen get reduced to at the end of the electron transport chain?

A. Water

B. Protons

C. Electrons

D. ATP

E. NADH

Answer 50

A. Water

Question 51

According to the animation, what does the electron transport chain do to the concentration of hydrogen ions (protons)?

A. The concentration of protons inside the membrane is equal to the concentration outside of the membrane.

B. The concentration of protons is lower outside the membrane than inside.

C. The concentration of protons is higher outside the membrane than inside.

Answer 51

C. The concentration of protons is higher outside the membrane than inside.

Question 52

The process of generating ATP using a proton gradient is referred to as

A. chemiosmosis.

B. water damming.

C. the electron transport chain.

Answer 52

A. chemiosmosis.

Question 53

Why does FADH₂ yield less ATP than NADH?

A. Electrons from FADH₂ cannot pump hydrogen ions out of the cell.

B. FADH₂ binds directly to the ATP synthase enzyme.

C. FADH₂ electrons enter the electron transport chain at a lower energy level.

D. FADH₂ electrons ultimately do not go to oxygen

Answer 53

C. FADH₂ electrons enter the electron transport chain at a lower energy level.

Question 54

Which of the following can be used as a final electron acceptor for aerobic respiration?

A. Nitrate ion, sulfate ion and carbonate ion can all be used as a final electron acceptor.

B. Sulfate ion

C. Molecular oxygen

D. Nitrate ion

E. Carbonate ion

Answer 54

C. Molecular oxygen

Question 55

What is one difference between ubiquinones and cytochromes?

A. Ubiquinones cannot carry electrons; cytochromes can.

B. Ubiquinones can only be reduced; cytochromes can only be oxidized.

C. Ubiquinones are not made of protein; cytochromes are.

D. Ubiquinones can only be oxidized; cytochromes can only be reduced.

Answer 55

C. Ubiquinones are not made of protein; cytochromes are.

Question 56

How does the proton gradient help ATP synthase to make ATP?

A. Protons move from inside the membrane to outside the membrane.

B. Protons move along the membrane.

C. Protons are not involved with this step; only electrons are.

D. Protons move from outside the membrane to inside the membrane.

Answer 56

D. Protons move from outside the membrane to inside the membrane.

Question 57

Iron is considered an essential element for many bacteria. Based on the animation, how would lack of iron affect energy production of a bacterium?

A. Lack of iron would mean that most of the oxygen could be reduced to form water, improving energy yields.

B. Lack of iron would mean lack of heme, and thus lower amounts of functioning cytochrome proteins. This would mean lower energy yields.

C. Lack of iron would not have any affect on this system.

Answer 57

B. Lack of iron would mean lack of heme, and thus lower amounts of functioning cytochrome proteins. This would mean lower energy yields.

Question 58

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 succinyl-CoA

C. only oxaloacetate

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

Answer 58

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

Question 59

If the citric acid cycle was interrupted after the reaction that forms citrate, predict how this would affect the total amount of ATP generated per glucose molecule.

A. The amount of ATP would be reduced from a total of 38 ATP to 8 ATP.

B. The amount of ATP would be reduced from a total of 38 ATP to 30 ATP.

C. The amount of ATP would be reduced from a total of 38 ATP to 22 ATP.

D. The amount of ATP would be reduced from a total of 38 ATP to 14 ATP.

Answer 59

D. The amount of ATP would be reduced from a total of 38 ATP to 14 ATP.

Question 60

What occurs at the bridge step?

A. The formation of succinyl CoA

B. The production of GTP

C. Decarboxylation of pyruvic acid

D. The formation of oxaloacetate

Answer 60

C. Decarboxylation of pyruvic acid

Question 61

Based on the animation, how many electron carriers are reduced in the Krebs cycle only?

A. Six

B. Four

C. Five

D. Three

Answer 61

B. Four

Question 62

What is the function of GTP?

A. A scaffolding for carbon atoms

B. An oxidizer to produce CO2

C. An energy carrier

D. An electron carrier

Answer 62

C. An energy carrier

Question 63

What is the fate of metabolites during respiration?

A. They are oxidized completely to form pyruvic acid.

B. They are rearranged to form GTP.

C. They are reduced to from NADH and FADH2.

D. They are oxidized completely to carbon dioxide and water.

Answer 63

D. They are oxidized completely to carbon dioxide and water.

Question 64

Which of the following is needed as a reactant for the first step of the citric acid cycle?

A. Malic acid

B. Citric acid

C. Oxaloacetic acid

D. Succinyl CoA

Answer 64

C. Oxaloacetic acid

Question 65

Where does the energy come from to power the formation of GTP?

A. ATP

B. NADH

C. Water

D. Succinyl CoA

Answer 65

D. Succinyl CoA

Question 66

Which step involves the release of carbon dioxide?

A. The third and fourth steps

B. The second step

C. The seventh step

D. The first and eighth steps

Answer 66

A. The third and fourth steps

Question 67

How many molecules of ATP can be generated from one molecule of NADH?

A. One

B. Four

C. Two

D. Three

Answer 67

D. Three

Question 68

Which step(s) of the Krebs cycle does (do) not produce any usable energy?

A. The sixth step

B. The third step

C. The second and seventh steps

D. The fifth step

E. The first and eighth steps

Answer 68

C. The second and seventh steps

Question 69

Fermentation occurs when there is no usable external electron acceptor (like O2) available for respiration. Fermentation products are made following glycolysis as a result of reactions that __________.

A. get rid of toxic waste products generated during glycolysis

B. synthesize more NAD+ from substrate molecules

C. generate more ATP energy from the substrate

D. oxidize NADH so that NAD+ can be reused again in glycolysis

Answer 69

D. oxidize NADH so that NAD+ can be reused again in glycolysis

Question 70

The Embden-Meyerhof-Parnas pathway is another name for

A. the citric acid cycle.

B. electron transport.

C. NADH production.

D. glycolysis.

Answer 70

D. glycolysis.

Question 71

The net gain of ATP per molecule of glucose fermented is

A. 4.

B. 8.

C. 2.

D. 1.

Answer 71

C. 2.

Question 72

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

A. glycogen

B. adenosine triphosphate

C. H2

D. acetyl~S-CoA

Answer 72

A. glycogen

Question 73

Fermentation has a relatively low ATP yield compared to aerobic respiration because

A. oxidative phosphorylation yields a lot of ATP.

B. less ATP is consumed during the first stage of aerobic catabolism.

C. substrate-level phosphorylation yields a lot of ATP.

D. more reducing equivalents are used for anaerobic catabolism.

Answer 73

A. oxidative phosphorylation yields a lot of ATP.

Question 74

The rising of bread dough is the result of

A. biotin production.

B. oxygen being released.

C. oxidative phosphorylation.

D. carbon dioxide produced by fermentation.

Answer 74

D. carbon dioxide produced by fermentation.

Question 75

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

A. True

B. False

Answer 75

A. True

Question 76

Microbial growth on the two-carbon acetate substrate invokes

A. both the citric acid and glyoxylate pathways.

B. the citric acid cycle for aerobic catabolism.

C. the glyoxylate pathway.

D. the glyoxylate and glycolysis pathways.

Answer 76

A. both the citric acid and glyoxylate pathways.

Question 77

During electron transport reactions

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

B. both OH- and H+ accumulate on the inside of the membrane.

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

D. both OH- and H+ accumulate on the outside of the membrane.

Answer 77

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

Question 78

How does the proton motive force lead to production of ATP?

A. Oxidative phosphorylation of ADP by ATP synthase requires protons as cofactors in the reaction.

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

C. ATPase requires one proton to make one ATP.

D. 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.

Answer 78

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

Question 79

Whether a molecule is oxidized or reduced in a redox reaction depends on its reduction potential relative to the available electron donors and acceptors present that the organism can utilize. Given the following reduction potentials for various redox half reactions, in a lithotroph capable of utilizing ammonia as an energy source, which substances would be potential terminal electron acceptors for respiration?

NO₂-/NH₃ +0.34 V
NO₃-/NO₂- +0.43 V
O₂/H₂O +0.82 V

A. O₂

B. Both O₂ and NO₃ - are possible electron acceptors

C. NO₃-

D. NO₂-

Answer 79

B. Both O₂ and NO₃ - are possible electron acceptors

Question 80

Which is one major difference between anaerobic and aerobic respiration?

A. electron acceptor

B. use of electron transport

C. electron donor

D. use of proton motive force

Answer 80

A. electron acceptor

Question 81

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

A. water.

B. nitrate.

C. FMN.

D. NADH.

Answer 81

B. nitrate.

Question 82

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

A. photoautrophy

B. chemoorganotrophy

C. aerobic catabolism

D. fermentation

Answer 82

D. fermentation

Question 83

• Translation (making protien)
• Protien
• DNA
• RNA
• Mechanisms of controlling enzyme activity
• Transcription (making RNA)

Answer 83

Question 84

Which of the following genetic elements is transcribed into a single mRNA?

A. The structural genes

B. The inducer

C. The operator

D. The repressor

E. The promoter

Answer 84

A. The structural genes

Question 85

Which operons are always transcribed unless deactivated?

A. Inducible operons

B. Repressible operons

C. Inducible and repressible operons

Answer 85

B. Repressible operons

Question 86

Which operons are never transcribed unless activated?

A. Inducible operons

B. Repressible operons

C. Inducible and repressible operons

Answer 86

A. Inducible operons

Question 87

According to the animation, where on the DNA strand does a repressor bind?

A. The operator

B. The promoter

C. The structural genes

D. The inducer

Answer 87

A. The operator

Question 88

What would be the most likely effect of a mutation in the operator of a lac operon?

A. beta-galactosidase would not be produced.

B. Regulation would occur normally.

C. The genes would be constitutively expressed.

D. The repressor would not be produced.

Answer 88

C. The genes would be constitutively expressed.

Question 89

To determine if you have identified a functional open reading frame (ORF), you should have found __________ within the sequence.

A. a start codon

B. < 300 nucleotides

C. a start codon and a ribosomal binding site (RBS)

D. a ribosomal binding site (RBS)

Answer 89

C. a start codon and a ribosomal binding site (RBS)

Question 90

Functional analysis of the genome of a prokaryote shows that 20% of the genome is for metabolism, 1% for biosynthesis of amino acids, 8% for peptide ABC transporters, and 2% for replication. What can you determine about the environment this organism lives in?

A. The organism lives in an environment rich in organic material, particularly amino acids and proteins.

B. The organism lives in an environment rich in hydrocarbons.

C. The organism lives in an environment rich in lipids.

D. The organism lives in an environment rich in sugars.

Answer 90

A. The organism lives in an environment rich in organic material, particularly amino acids and proteins.

Question 91

Answer 91

Question 92

One reason that regulation of gene expression is important is that it saves energy and materials from being used when they are not needed. Although most genes have more than one form of regulation acting upon them, at which point would regulation be most efficient in conserving energy and materials if the product of a gene is not needed?

A. regulation of translation

B. post-translational regulation

C. transcriptional regulation (regulation of whether transcription occurs)

D. post-transcriptional regulation

Answer 92

C. transcriptional regulation (regulation of whether transcription occurs)

Question 93

Cells can regulate their metabolism by regulating enzyme activity or by regulating enzyme synthesis (i.e., by regulating whether they produce the enzyme that catalyzes a reaction). Which of the following examples would be the best form of regulation when an enzyme needs to be available very rapidly?

A. When the enzyme is needed, the relevant operon that contains its gene is repressed.

B. Until the enzyme is needed, mRNA transcripts are produced but not translated.

C. An enzyme is activated by the binding of a molecule to its allosteric site.

D. When the enzyme is needed, the relevant operon that contains its gene is activated.

Answer 93

C. An enzyme is activated by the binding of a molecule to its allosteric site.

Question 94

Proteins required at approximately the same level throughout a cells growth cycle are often not subject to regulatory mechanisms and are constitutively synthesized.

A. True

B. False

Answer 94

A. True

Question 95

Some proteins that bind to DNA block transcription, whereas other proteins activate transcription.

A. True

B. False

Answer 95

A. True

Question 96

When arginine is added to a culture already growing exponentially in a medium without arginine, what occurs?

A. The cell returns to the lag stage of growth to synthesize the proteins necessary for the metabolism of arginine.

B. All cellular growth ceases.

C. Growth continues, but the production of enzymes required for the synthesis of arginine ceases.

D. Growth continues, but the production of enzymes required for the synthesis of arginine increases.

Answer 96

C. Growth continues, but the production of enzymes required for the synthesis of arginine ceases.

Question 97

Enzyme induction occurs

A. when the substrate is present.

B. continuously.

C. when the organism is environmentally stressed.

D. when the substrate is depleted.

Answer 97

A. when the substrate is present.

Question 98

In negative control of transcription by the lac operon, how does the presence of an inducer affect transcription?

A. The inducer does not bind to the operator.

B. The inducer prevents the repressor from binding to the operator.

C. The inducer causes the repressor to bind to the operator.

D. The inducer binds to the operator.

Answer 98

B. The inducer prevents the repressor from binding to the operator.

Question 99

Which of the following do NOT bind to the promoter sequence during regulation?

A. repressors

B. inducers

C. activators

D. None of these bind directly to the promoter sequence.

Answer 99

D. None of these bind directly to the promoter sequence.

Question 100

The promoters of positively controlled operons require activator proteins because

A. RNA polymerase easily recognizes the consensus sequence.

B. the promoters bind RNA polymerase weakly and utilize activator proteins to help RNA polymerase recognize the promoter.

C. they are needed to bind to the allosteric site of RNA polymerase.

D. they are required to inactivate the repressor proteins.

Answer 100

B. the promoters bind RNA polymerase weakly and utilize activator proteins to help RNA polymerase recognize the promoter.

Question 101

Which statement is TRUE of two separate regulators controlling one individual operon?

A. One regulator will likely control the transcription of one section of the operon, whereas the other regulator will control the other component.

B. The two regulators themselves must respond to different signals, which enables both to control the operon differently.

C. Two regulators trying to control the same operon will likely result in only one being maintained after several generations.

D. One regulator will bind to the operator region whereas the other will bind to the promoter region so they can co-occur and co-regulate the operon.

Answer 101

B. The two regulators themselves must respond to different signals, which enables both to control the operon differently.

Question 102

The synthesis of β-galactosidase is regulated by __________.

A. induction

B. induction and catabolite repression

C. catabolite repression

D. repression

Answer 102

B. induction and catabolite repression

Question 103

In certain circumstances, a single regulatory protein controls multiple operons. This situation would be called a(n) __________.

A. genetic regulation

B. regulon

C. multiple operon

D. catabolite regulation

Answer 103

B. regulon

Question 104

DNA replication always proceeds in only one direction because the ________ of the incoming nucleotide is attached to the free ________ of the growing DNA strand.

A. 3-phosphate / 5-hydroxyl

B. 3-base / 5-deoxyribose

C. 5-deoxyribose / 3-base

D. 5-phosphate / 3-hydroxyl

Answer 104

D. 5-phosphate / 3-hydroxyl

Question 105

Which of the following is formed on the lagging strand during DNA synthesis?

A. DNA secondary structures

B. replisomes

C. Okazaki fragments

D. RNA polymerase

Answer 105

C. Okazaki fragments

Question 106

Which of the following is NOT correct regarding DNA and RNA synthesis?

A. Both processes require an RNA primer to begin.

B. The template strand is antiparallel to the newly synthesized strand.

C. DNA is the template for both DNA and RNA synthesis.

D. The overall direction of chain growth is from the 5 to 3 end.

Answer 106

A. Both processes require an RNA primer to begin.

Question 107

The function of the DNA polymerase is to catalyze

A. the formation of RNA primers.

B. hydrogen bonding between complementary base pairs.

C. the addition of deoxynucleotides.

D. the addition of ribonucleotides.

Answer 107

C. the addition of deoxynucleotides.

Question 108

DNA replication is started with a(n) ________, which, in most cases, in vivo is a short stretch of ________.

A. mRNA / RNA

B. primer / RNA

C. promoter / DNA

D. ribosome-binding sequence / DNA

Answer 108

B. primer / RNA

Question 109

During DNA replication Okazaki fragments are linked together by ________, an enzyme that creates phosphodiester bonds between nicked fragments of DNA.

A. DNA gyrase

B.exopolymerase

C. topoisomerase

D. DNA ligase

Answer 109

D. DNA ligase

Question 110

In DNA replication there are leading and lagging strands, because

A. DNA replication is semiconservative and each strand is copied simultaneously in opposite directions.

B. DNA replication is conservative and a completely new DNA molecule must be made.

C. the strands of DNA are parallel and are copied in the same direction simultaneously.

D. one strand of DNA is copied faster than the other.

Answer 110

A. DNA replication is semiconservative and each strand is copied simultaneously in opposite directions.

Question 111

Which statement illustrates why DNA polymerase cannot initiate a new DNA strand?

A. DNA polymerase requires a preexisting 3’-phosphate group in order to add nucleotides.

B. DNA polymerase requires a preexisting 3’-hydroxyl group in order to add nucleotides.

C. DNA polymerase requires a preexisting 5’-phosphate group to add nucleotides.

D. DNA polymerase requires a preexisting 5’-hydroxyl group in order to add nucleotides.

Answer 111

B. DNA polymerase requires a preexisting 3’-hydroxyl group in order to add nucleotides.

Question 112

Proofreading of newly-synthesized DNA is important because __________.

A. a high fidelity in the copying of DNA is necessary for good heredity

B. DNA pol III has a high error rate during replication

C. any protein made from mutated DNA will not function properly

D. the cell will invariably die if any mutations occur during replication

Answer 112

A. a high fidelity in the copying of DNA is necessary for good heredity

Question 113

The replisome is a large complex of proteins that contains many enzymes involved in DNA replication. Hypothesize why these enzymes function best together.

A. With the replisome, it can replicate both strands of DNA at the same time.

B. With the replisome, the strands of DNA can be copied one at a time.

C. With the replisome, mRNA can be transcribed faster.

D. With the replisome, plasmids can be replicated along with the chromosome.

Answer 113

A. With the replisome, it can replicate both strands of DNA at the same time.

Question 114

Which of the following is/are transferred to daughter cells during bacterial cell division?

A. individual genes and enzymes to later be brought together to form the genome

B. only genomic DNA, the blueprint for everything the cell needs

C. chromosome, proteins, and all other cellular constituents

D. only the chromosome and enzymes to immediately begin cellular metabolism

Answer 114

C. chromosome, proteins, and all other cellular constituents

Question 115

Which of the following methods used to enumerate cells often requires specialized staining to observe non-pigmented bacteria?

A. spread-plating, turbidity, and microscopy

B. spread-plating

C. spectrophotometry/turbidity

D. microscopy

Answer 115

D. microscopy

Question 116

In a bacterial cell undergoing binary fission and balanced growth, __________.

A. the time it takes to complete one round of DNA replication limits the generation time

B. the proportion of all cell constituents will remain the same over time

C. the proportion of DNA in the cell increases rapidly until the cell divides

D. the proportion of protein in the cell increases

Answer 116

B. the proportion of all cell constituents will remain the same over time

Question 117

If a bacterial culture contains 1 cell at time zero, 4 cells after 1 hour, and 16 cells after 2 hours, then all EXCEPT which of the following are true?

A. The generation time, g, is constant.

B. The culture is in exponential phase.

C. The growth rate is constant.

D. The growth rate is increasing with each generation.

Answer 117

D. The growth rate is increasing with each generation.

Question 118

If a bacterial cell culture contains 2 cells at time zero, 8 cells 1 hour later, 32 cells after 2 hours, and 128 cells after 4 hours, then which of the following describes the growth of this culture if h = hours, g = the generation time, and k = the instantaneous growth rate?

A. g = 0.5 h, k = 5.386 h-1

B. g = 1 h, k= 1 h-1

C. g = 1.386 h, k = 0.5 h-1

D. g = 0.5 h, k = 1.386 h-1

Answer 118

D. g = 0.5 h, k = 1.386 h-1

Question 119

In a batch culture, bacterial cultures typically exhibit four different phases of growth. In which phase are the cells rapidly synthesizing proteins, but cell numbers are not changing?

A. exponential phase

B. lag phase

C. stationary phase

D. death phase

Answer 119

B. lag phase

Question 120

A closed system, used for bacterial growth, where nothing is added and nothing is removed is called __________.

A. a lag culture

B. a batch culture

C. a continuous culture

D. a chemosta

Answer 120

B. a batch culture

Question 121

Which choice best illustrates what occurs in the stationary phase of bacterial growth?

A. cryptic growth, where the number of dead cells decreases while the number of new cells increases

B. unbalanced growth, where the number of dead cells increases while the number of new cells decreases

C. cryptic growth, where the number of new cells equals the number of dying cells

D. balanced growth, where the number of dead cells equals the number of new cells

Answer 121

C. cryptic growth, where the number of new cells equals the number of dying cells

Question 122

A student has a pure culture of bacteria growing in a flask and wants to know how many living cells are in the culture at a given time. Which method should she employ to get an estimate?

A. microscopic counts

B. turbidity measurements

C. plate counts

D. Any of these methods would work equally well in this case, assuming that standard curves are produced.

Answer 122

C. plate counts

Question 123

When attempting to determine viable cell counts of a heat-sensitive bacterial isolate, which cell counting method should be avoided?

A. spread-plate method

B. pour-plate method

C. both spread- and pour-plate methods

D. live staining and direct counting with a microscope

Answer 123

B. pour-plate method

Question 124

Relative to enzymes in mesophilic microorganisms, which of the following is NOT characteristic of enzymes in psychrophiles?

A. decreased alpha helix content

B. decreased beta sheet content

C. fewer ionic bonds

D.fewer hydrogen bonds

Answer 124

A. decreased alpha helix content

Question 125

Which of the following statements is FALSE?

A. The generation time of bacteria may vary from species to species.

B. In the lag phase, cell death exceeds cell division.

C. Bacteria typically divide by binary fission, producing two daughter cells.

D. In the death phase, bacterial growth may cease as a result of oxygen and nutrient depletion.

Answer 125

B. In the lag phase, cell death exceeds cell division.

Question 126

Direct microscopic counting of cells is an accurate method for estimating the number of viable cells in a sample.

A. True

B. False

Answer 126

B. False

Question 127

Turbidity measurements are commonly utilized for monitoring

A. planktonic cultures.

B. colonies.

C. biofilms.

D. sessile cultures.

Answer 127

A. planktonic cultures.

Question 128

Optical density and viable cell concentration are LEAST proportional to each other during the

A. exponential growth phase.

B. death phase.

C. stationary phase.

D. lag phase.

Answer 128

B. death phase.

Question 129

The number of organisms in a broth culture was determined using the standard plate count method (SPC) and spectrophotometry (SPEC). Which of the results below would you expect to see from each method?

A. SPC = 12 × 106 cfu/ml; SPEC = 12 × 106 cfu/ml

B. SPC = 12 × 107 cfu/ml; SPEC = 11 × 103 cfu/ml

C. SPC = 100 cfu/ml; SPEC = 10 cfu/ml

D. SPC = 12 × 106 cfu/ml; SPEC = 11 × 107 cfu/ml

Answer 129

D. SPC = 12 × 106 cfu/ml; SPEC = 11 × 107 cfu/ml