Exam questions

Question 1

iron sulfer clusters (2Fe-2S) and (4Fe-4S) are coordinated by sulfur atoms of BLANK residues in the surrounding protein

Alanine

Lysine

Guanine

Cysteine

Tryptophan

Answer 1

Cysteine

Question 2

A respiratory electron transport system includes these functional components

a. an initial substrate oxidoreductase
b. mobile electron carrier
c. a terminal oxidase
d. all of the above
e. a and b only

Answer 2

d. all of the above

Question 3

In the “glucose activation stage” of glycolysis (EMP pathway), glucose is activated, consuming BLANK and ultimately converting it to fructose 1-6 diphosphate

a. 1 NADPH
b. 2 ATP
c. 2 NADH
d. 1 FADH2

Answer 3

b. 2 ATP

Question 4

Which of the following is a mechanism in which CO2 can be fixed that is believed to be the original mechanism for biomass generation in the acestors of all 3 living domains

a. calvin cycle
b. reductive (reverse) TCA
c. acetyl-CoA cycle
d. none of the above

Answer 4

b. reductive (reverse) TCA

Question 5

In this pathway, glucose 6-P is oxidized to 6-phosphogluconate, with one pair of electrons transferred to NADPH. The net yield from this pathway is 2 pyruvate, 1 ATP, 1 NADPH, and 1 NADH

a. Etner-Doudroff pathway
b. Embden-meyerhof-parnas pathway
c. calvin cycle
d. TCA cycle
e. Pentose phosphate pathway

Answer 5

a. Etner-Doudroff pathway

Question 6

In fatty acid biosynthesis, after acetyl-coa is activated by condensation with CO2, coenzyme A is replaced by the acyl carrier protein, making BLANK

a. Acetyl-CoA
b. Acetyl-ACP
c. Malonyl-ACP
d. all of the above
e. none of the above

Answer 6

c. Malonyl-ACP

Question 7

after a growing polyketide antibiotic precursor has been synthesized, this elongation is terminated by BLANK, which hydrolyzes the bond to the final ACP

a. acyltransferase
b. keto-synthase
c. dehydrolase
d. enoyl reductase
e. thioesterase

Answer 7

e. thioesterase

Question 8

Choose the INCORRECT statement about the Pentose Phosphate Pathway

a. one step involves the oxidation of 6-phosphogluconate by NADP+, resulting in the loss of carbon as CO2

b. In succeeding steps, pairs of sugars exchange short carbon chains giving rise to sugar phosphates of various lengths

c. this pathway produces 1 ATP and 0 NADH, but 2 ATPS

d. this pathway is believed to have evolved earlier than the EMP pathway because it requires fewer phosphorylation steps, produces less ATP, and is found in a wide variety of bacteria and archae

Answer 8

d. this pathway is believed to have evolved earlier than the EMP pathway because it requires fewer phosphorylation steps, produces less ATP, and is found in a wide variety of bacteria and archae

Question 9

Blank fermentation produces one molecule of lactic acid, one ethanol, and CO2

a. homolactic
b. ethanolic
c. heterolactic
d. mixed-acid fermentation
e. none of the above

Answer 9

c. heterolactic

Question 10

conversion of pyruvate to acetyl-CoA is catalyzed by a very large multisubunit enzyme called the pyruvate dehydrogenase complex (PDC). PDC activity is a key control point of catabolism, and it is BLANK when carbon sources are plentiful

a. Repressed
b. Induced

Answer 10

b. induced

Question 11

At each oxidative decarboxylation step in the TCA cycle, a CO2 is given off and a molecule of BLANK is produced

a. ATP
b. GTP
c. NADH
d. NADPH
e. FADH2

Answer 11

c. NADH

Question 12

after the complete oxidative breakdown of a single molecule of glucose to CO2 and H2O could theoretically generate up to BLANK ATP.

a. 38
b. 34
c. 28
d. 16
e. 8

Answer 12

a. 38

Question 13

When glucose is scarce, cells can catabolize acetate or fatty acids using a modified TCA cycle called the glyoxylate shunt

a. true
b. false

Answer 13

a. true

Question 14

Metabolism that involves moving electrons through an electron transport system is called BLANK

a. respiration
b. fermentation
c. anabolism
d. autotrophy
e. none of the above

Answer 14

a. respiration

Question 15

In the 2nd energy yielding sage of glycolysis (EMP pathway), how many molecules of glyceraldehyde-3-phosphate enter the pathway per molecule of glucose?

a. 1
b. 2
c. 3
d. 4
e. 6

Answer 15

b. 2

Question 16

The net yield from a single molecule of glucose in glycolysis (EMP Pathway) is Blank

a. 2 pyruvate, 2 atp, and 2 nadh
b. 2 pyruvate, 1 atp, 1 NADH, and 1 NADPH
c. 2 pyruvate, 2 atp, and 1 nadh
d. various sugar phosphates for biosynthesis, 1 atp, and 2 nadph
e. 2 pyruvate, 2 atp, and 2 nadph

Answer 16

a. 2 pyruvate, 2 atp, and 2 nadh

Question 17

Catabolism that results in the partial breakdown of organic compounds without the net electron transfer to an inorganic terminal electron acceptor is called:

a. aerobic pathways
b. photoheterotrophy
c. fermentation
d. anaerobic respiration
e. none of the above

Answer 17

c. fermentation

Question 18

An electron transport system passes electrons through cytochromes. Each cytochrome in turn receives electrons from a stronger electron donor and transfers them to a stronger electron acceptor. The end result is

a. a net gain in NADH and H+
b. a reduction in proton proton potential
c. lower charge difference
d. an H+ concentration difference plus charge difference which is proton potential
e. an oxidized terminal electron acceptor and proton potential

Answer 18

d. an H+ concentration difference plus charge difference which is proton potential

Question 19

As part of the ETS, the NADH:quinone oxidoreductase complex (NDH-1) transfers two electrons from NADH onto FMN (FMNH₂), through several Fe-S
centers, and ultimately onto a _____. The energy from oxidizing NADH is coupled to pumping H⁺ across the cell membrane. (Choose the BEST answer)

a. quinone, Q (forming quinol, QH₂)
b. a substrate oxidoreductase
c. quinol, Q (forming quinone, QH₂)
d. ADP, with P forming ATP
e. NAD⁺ with H⁺, forming NADH

Answer 19

a. quinone, Q (forming quinol, QH₂)

Question 20

processes powered by proton potenial include:

a. atp synthesis through ATP synthase
b. flagellar rotation
c. uptake of nutrients
d. efflux of toxic drugs
e. all of the above

Answer 20

e. all of the above

Question 21

ETS proteins such as cytochromes associate electron transfer with small, reversible, energy transitions, which are mediated by cofactors.

a. True
b. False

Answer 21

a. true

Question 22

This component of the electron transport system receives electrons from a quinol (QH₂) and transfers them to a terminal electron acceptor, such as O₂, releasing 2H⁺ out to the periplasm.

a. Terminal oxidase
b. F₀F₁ ATP Synthase
c. Substrate oxidoreductase (dehydrogenase)
d. Quinone pool
e. A and C only

Answer 22

a. Terminal oxidase

Question 23

How does the mitochondrial (eukaryotic) electron transport system differ from bacterial electron transport system?

a. Mitochondria only have a single ETS, no alternatives to use during starvation or varying energy conditions.

b. The mitochondrial ETS pumps fewer protons per NADH

c. Mitochondria contain an intermediate cytochrome oxidase complex that also transfers electrons

d. All of the above

e. A and C only

Answer 23

e. A and C only

Question 24

The F₀F₁ ATP synthase is a highly conserved protein complex. Where does the interconversion of ADP + Pᵢ with ATP + H₂O occur? (Choose all correct answers, may be more than one.)

a. On the periplasmic side of the membrane
b. In the cytoplasm
c. Within the F₀ complex
d. Within the membrane
e. Within the F₁ complex

Answer 24

In the cytoplasm

Within the F₁ complex

Question 25

In some bacteria (e.g., the pathogens Vibrio cholerae and Yersinia pestis), an ETS oxidoreductase pumps _____ instead of H⁺. a. Mg²⁺ b. Cl⁻ c. Fe²⁺ d. Na⁺ e. Ca²⁺

Answer 25

d. Na⁺

Question 26

In chlorophyll-containing phototrophs, antennae complexes associate in a ring around the reaction center, which is where chlorophyll photoexcitation connects to the ETS. a. True b. False

Answer 26

a. true

Question 27

In purple bacteria, the efficiency of photon uptake is increased even more by the presence of extensive backfolding of the photosynthetic membranes in oval pockets. These structures are called… a. Photopigments b. Chlorophylls c. Bacteriorhodopsins d. Carboxysomes e. None of the above

Answer 27

e. None of the above

Question 28

Each photoexcited electron enters an ETS. (Choose the MOST correct statement below) a. In PS I, electrons separated from H₂O or H₂S are transferred to NADP⁺ to form NADPH b. In PS II, the electron separated from bacteriochlorophyll is replaced by an electron returned from the ETS c. In the oxygenic Z pathway (H₂O photolysis), electrons flow from PS II into PS I, ultimately releasing O₂ from H₂O d. All of the above e. None of the above

Answer 28

d. All of the above

Question 29

Which photosystem below generates the most potential energy (i.e., reduction potential)? a. Photosystem I b. Photosystem II c. Proteorhodopsin d. Bacteriorhodopsin e. Chlorophyll

Answer 29

a. Photosystem I

Question 30

What is the protein complex that links the electrons that flow from PS II to PS I in the Z pathway of oxygenic photosynthesis? a. Plastocyanin b. Ferredoxin c. Quinone d. Cytochrome b₆f e. None of the above

Answer 30

a. Plastocyanin

Question 31

An accessory pigment that absorbs the midrange of light wavelengths but does not directly conduct photolysis… a. Bacteriorhodopsin b. Chlorophyll c. Bacteriochlorophyll d. Carotenoid e. None of the above

Answer 31

d. Carotenoid

Question 32

Bacteriorhodopsin is a small membrane protein that participates in a simple form of phototrophy. This protein complex consists of seven hydrophobic alpha helices that span the membrane in alternating directions. These surround a molecule of ______. Photon absorption causes an electron in one of the double bonds to be excited to a higher energy level. The cycle of excitation (cis configuration) and relaxation back to trans is coupled with the pumping of 1 H⁺ from the cytoplasm across the membrane. a. Heme b. Cytochrome c. Rhodopsin d. Quinoline e. Retinal

Answer 32

e. Retinal

Question 33

Each type of chlorophyll contains a characteristic chromophore, which consists of a heteroaromatic ring complexed to ______. a. Mg²⁺ b. Fe²⁺ c. A heme group d. Na⁺ e. Cu²⁺

Answer 33

a. Mg²⁺

Question 34

Which of the photosystems requires reverse electron flow in order to generate NADPH or NADH? a. Thylakoids b. Photosystem I c. Photosystem II d. Oxygenic Z pathway e. None of the above

Answer 34

c. Photosystem II

Question 35

Unlike cytoplasmic redox reactions, a membrane-embedded ETS can convert its energy into an ion potential or electrochemical potential, generating a “proton motive force,” accumulating protons on the inside of the cytoplasmic membrane. a. True b. False

Answer 35

b. false

Question 36

The reduction potential is a measure of the tendency of a molecule to accept electrons. A positive value of E₀′ has a ______ ΔG, so the gain of electrons yields energy. a. Positive b. Negative

Answer 36

b. negative

Question 37

Which of the following is a pathway for fixing two molecules of CO₂ and is used by soil bacteria, sulfate reducers, and methanogens? Bacteria use a complex carrier cofactor tetrahydrofolate and methanogens use methanopterin in this pathway… a. Calvin cycle b. Reductive (reverse) TCA cycle c. Acetyl-CoA pathway d. 3-Hydroxypropionate cycle e. None of the above

Answer 37

d. 3-Hydroxypropionate cycle

Question 38

In all, three molecules of CO₂ are fixed into one molecule of pyruvate, which serves as a substrate for biosynthesis in this mechanism for CO₂ fixation. This mechanism is used by thermophiles, such as the bacterium Chloroflexus and the archaea Sulfolobus metallicus and Acidianus brierleyi… a. Calvin cycle b. Reductive (reverse) TCA cycle c. Acetyl-CoA pathway d. 3-Hydroxypropionate cycle e. None of the above

Answer 38

b. Reductive (reverse) TCA cycle

Question 39

46. The single, interlinked molecule that is the main component of the bacterial cell wall: a. Phospholipid b. Peptidoglycan c. Glycolipid d. Pseudomurein e. None of the above

Answer 39

b. Peptidoglycan

Question 40

During peptidoglycan cross-bridge formation between adjacent peptide chains, the terminal amino acid ______ is released: a. L-Alanine b. D-Glutamic acid c. M-Diaminopimelic acid d. L-Leucine e. D-Alanine

Answer 40

. D-Alanine

Question 41

Gram-positive cell envelopes contain which of the following? a. Teichoic acids b. S-layer c. Peptidoglycan d. All of the above e. A and B only

Answer 41

d. All of the above

Question 42

Where would a Chemolithoautotroph get its carbon? a. organic molecules b. light energy c. CO2 d. inorganic molecules

Answer 42

c. CO2

Question 43

Once the A site is filled, ______ activity makes a peptide bond between the amino acid or peptide in the P site and the amino acid in the A site: a. Peptidyltransferase b. Translational c. Helicase d. Proofreading e. None of the above

Answer 43

a. Peptidyltransferase