BCHS 3305 Fall 2009 Exam #2 (Answers on last page) 10/12/09

Multiple-Choice. Choose one answer for each question. Each correct answer gets two points. A wrong answer or no answer gets zero point but no extra penalty.

On your answer sheet, identify (a) your name AND (b) the last four digits of your UH student #

Ø [ (a) NAD+; (b) NADH; (c) NADP+; (d) NADPH]

Each of the above participates in many biological oxidation-reduction reactions either as a co-substrate (or active cofactor) or as a product. Choose from the above list to fill in the following blanks.

• The glycolysis reactions (from glucose to pyruvate) can produce (#1) _____ as a product.

• In the glycerophosphate shuttle, a dehydrogenase in cytosol uses (#2) _____ as a substrate for the conversion of dihydroxyacetone phosphate to 3-phosphoglycerol.

• In the Calvin cycle dark reactions, the conversion of 1,3-bisphosphoglycerate to glyceraldehyde-3-phosphate requires (#3) _____ as a substrate.

Ø The oxidation of one acetyl-CoA to 2 molecules of CO₂ by one complete citric acid cycle can produce a total reducing equivalents of (#4) _____ electrons.

[(a) 8 (or 4 pairs); (b) 10 (or 5 pairs); (c) 12 (or 6 pairs); (d) none of the above]

These reducing equivalents are in the form of (#5) _____.

[(a) NADH only; (b) FADH₂ only; (c) NADPH only; (d) NADH and FADH₂; (e) NADPH and FADH₂]

Ø Aspartate can be transported across mitochondrial inner membrane by a (or an) (#6) _____ transport system, and malate can be transported across mitochondrial inner membrane by a (or an) (#7) _____ transport system.

[(a) direct; (b) indirect] (Definitions: Direct = the molecule itself is transported across the membrane. Indirect = one molecule is consumed on one side and one molecule of the same kind is generated on the other side of the membrane.)

Ø The mitochondrial ADP-ATP translocator can transport ADP and ATP in both directions across the mitochondrial inner membrane. However, due to a membrane potential difference across the mitochondrial inner membrane under normal cell physiological conditions, there is a NET transport of (#8) _____ from cytosol into mitochondrial matrix in exchange of a NET transport of (#9) _____ from mitochondrial matrix to cytosol.

[(a) ATP; (b) ADP]

Ø During the cycle 1 of the Q cycle, a total of (#10) _____ is/are transferred from one QH₂ to Cyt c₁ for the pumping of 2 H⁺s to cytosol.

[(a) 1 electron; (b) 2 electrons]

Ø The standard redox potentials (Eº’) for the following two reactions are:

NAD+ + H+ +2e D NADH Eº’ = -0.315 V

Q + 2H+ + 2e D QH2 Eº’ = 0.045 V

Therefore, the standard redox potential change (DEº’) for the following reaction (from left to right) QH₂ + NAD+ D NADH + H+ + Q should be (#11) _____ .

[(a) -0.360 V; (b) -0.270 V; (c) 0.270 V; (d) 0.360 V]

Ø From the standard redox poptential point of view, QH₂ is a (#12) _____ reductant than reduced Cytochrome c under standard conditions. [(a) weaker; (b) stronger]

Ø For electron transport by mitochondria under physiological conditions, the overall reaction catalyzed by the complex III is the reduction of (#13) _____ .

[ (a) NAD⁺; (b) FAD; (c) coenzyme Q; (d) cytochrome c; (e) O2]

Ø The addition of an uncoupler such as 2,4-dinitrophenol to a suspension of mitochondria will lead to inhibition of the activity of (#14) _____ .

[ (a) complex I; (b) complex II; (c) complex III; (d) complex IV; (e) none of the above]

Ø When electrons are passed from FMNH₂ to an oxidized iron-sulfur cluster, protons (#15) _____ the surrounding medium.

[(a) must be abstracted from; (b) must be released to; (c) will be neither abstracted from nor released to]

Ø According to the proton pump mechanism for the generation of a proton gradient across the inner mitochondrial membrane, an amino acid residue that is a strong acid can (#16) _____ a neighboring amino acid residue that is a strong base.

[(a) donate proton(s) to; (b) abstract proton(s) from]

Ø The mechanism of H⁺ gradient-driven synthesis of ATP by mitochondrial ATP synthase is believed to involve energy-dependent conformational changes in F₁. Specifically, F₁ has three conformationally distinct forms (or sites) referred to as: [(a) O; (b) L; (c) T]

• Initially, the binding sites of O and L forms are empty and ATP is bound to the T form. Next, ADP and Pi bind to the (#17) _____ form.

• Subsequently, the H⁺ translocation takes place and results in conformational changes of all three forms. Such conformational changes include the conversion of the original O form to the new (#18) _____ form.

• Immediately after such conformational changes, ATP is synthesized by the NEW (#19) _____ form of subunit.

Ø Under normal cellular conditions, the mitochondrial matrix is (#20) _____ the cytosolic medium.

[ (a) more negatively charged than; (b) more positively charged than; (c) similar in membrane potential as]

Ø Oxidative phosphorylation is carried out using a mitochondria suspension in the presence of ADP, Pi, and other components as shown below. For the following questions, choose the expected value of P/O (or P/2e) ratios for ATP formation that can occur under a continuous operational condition.

Inhibitor or P/O or

Electron Donor Electron Acceptor Uncoupler Added P/2e Ratio

NADH 1/2 O2 CN– (#21) _____

succinate Fe(CN)63– rotenone (#22) _____

NADH Fe(CN)63– 2,4-dinitrophenol (#23) _____

ascorbate Fe(CN)63– none (#24) _____

FADH₂ 1/2 O₂ Amytal (#25) _____

[(a) 0; (b) 1; (c) 2; (d) 3]

Ø Chlorophylls are (#26) _____-containing porphyrins.

[(a) iron; (b) copper; (c) magnesium; (d) manganese]

Ø The light-harvesting complex (or antenna complex) of chloroplast contains (#27) _____.

[(a) only a single species of chlorophyll and no other light-absorbing pigment; (b) a single species of chlorophyll plus other light-absorbing pigment(s); (c) multiple species of chlorophylls but no other light-absorbing pigment; (d) multiple species of chlorophylls plus other light-absorbing pigment(s)]

Ø The chloroplast photosynthetic reaction center chlorophylls can be excited by receiving energy transferred from the excited state of antenna complex, (#28) _____ be excited by directly absorbing photons from sunlight.

[(a) and can also; (b) but cannot]

Ø Photosynthesis consists of Dark reactions and Light reactions. The dark reactions can (#29) _____ . The light reactions can (#30) _____ .

[(a) never take place under light; (b) take place under light or in the dark; (c) never take place in the dark]

Ø The chloroplast photosynthetic light reactions can (#31) _____ water to generate O₂.

[(a) oxidize; (b) reduce]

Ø The photosynthetic light reactions involve two photosystems. The 670 nm light can activate (#32) _____ and the 690 nm light can activate (#33) _____.

[(a) only the photosystem I; (b) only the photosystem II; (c) both photosystems; (d) neither photosystems]

Ø By absorbing light, the photosystem II can generate a (#34) _____ reductant in the form of (#35) _____, and a (#36) _____ oxidant in the form of (#37) _____ .

[(a) weak; (b) strong; (c) P680; (d) P680*; (e) P680⁺]

Ø For the overall non-cyclic photosynthetic electron transport pathway, the formation of one O₂ and 2 NADPH require the absorption of a total of (#38) _____ quanta.

[(a) two; (b) four; (c) eight]

Ø In the non-cyclic photosynthetic electron transport pathway, the formation of one molecule of O₂ from 2 molecules of H₂O is directly coupled to a gain of 4 protons in the (#39) _____.

[(a) space between inner and outer membranes; (b) stroma; (c) thylakoid lumen]

Ø The final electron acceptor at the end point of the non-cyclic photosynthetic electron transport pathway is (#40) _____.

[(a) H₂O; (b) O₂; (c) H⁺; (d) NADP⁺]

Ø For each cycle of the cyclic photosynthetic electron transport pathway, four quanta are absorbed for the pumping of (#41) _____ H+ from stroma to thylakoid compartment.

[(a) two; (b) four; (c) eight]

Ø Under constant illumination of chloroplasts by 700 nm light, there will be (#42) _____ of NADPH by the light reactions.

[(a) absolutely zero production; (b) a small amount within a very brief period of time but no continuous formation; (c) a continuous formation]

Ø Under sunlight, chloroplasts can undergo (#43) _____ photosynthetic electron transport .

[(a) only the cyclic but not the non-cyclic; (b) only the non-cyclic but not the cyclic; (c) the cyclic and/or the non-cyclic]

Ø In photosynthesis, the overall process of dark reactions is endergonic (i.e. energy requiring). The net synthesis of one molecule of glyceraldehyde-3-phosphate by the dark reactions requires (#44) _____ molecules of ATP and (#45) _____ molecules of NADPH.

[(a) 6; (b) 9; (c) 12; (d) 18]

Ø In the Calvin cycle, the enzyme which catalyzes:

• the formation of ribose-5-phosphate and xylulose-5-phosphate from glyceraldehyde-3-phosphate and sedoheptulose-7-phosphate is a/an (#46) _____.

• the formation of dihydroxyacetone phosphate from glyceraldehydes-3-phosphate is a/an (#47) _____.

• the formation of ribulose-5-phosphate from xylulose-5-phosphate is a/an (#48) _____.

• the formation of fructose-1,6-bisphosphate from glyceraldehydes-3-phosphate and dihydroxyacetone phosphate is a/an (#49) _____.

• the incorporation of CO₂ into an organic metabolite is a/an (#50) _____.

[(a) transketolase; (b) aldolase; (c) isomerase; (d) epimerase; (e) carboxylase]

Answers: (1-B), (2-B), (3-D), (4-A), (5-D), (6-A), (7-A), (8-B), (9-A), (10-A), (11-A), (12-B), (13-D), (14-E), (15-B), (16-A), (17-B), (18-B), (19-C), (20-A), (21-A), (22-B), (23-A), (24-A), (25-C), (26-C), (27-D), (28-A), (29-B), (30-C), (31-A), (32-C), (33-A), (34-A), (35-D), (36-B), (37-E), (38-C), (39-C), (40-D), (41-C), (42-B), (43-C), (44-B), (45-A), (46-A), (47-C), (48-D), (49-B), (50-E)