Ch 19 Oxidative Phophorylation

Calculate the delta G for the production of 1 mol of O2 produced during photosynthesis assuming 700 nm light and the absorption of light energy is 100% efficient Select one: a. -920 kJ/mol b. 754000 J/mol c. -754 kJ/mol d. 920000 J/mol

a. -920 kJ/mol

A spinach leaf has 20 micro grams /cm2 of chlorophyll a (mw 892) in an leaf. If each leaf has a surface area of 10 cm2 and can absorb 50% of radiation (with an energy of 5.4 J/ cm2 *min) hitting it. How often will a single chlorophyll molecule absorb a photon? Select one: a. 0.1 s b. 3 picosec c. 0.5 sec d. 1 s

a. 0.1 s

In normal mitochondria, the rate of NADH consumption (oxidation) will: Select one: a. All of the above b. be very low if the ATP synthase is inhibited, but increase when an uncoupler is added c. decrease when cyanide is used to prevent electron transfer through the cytochrome a + a3 complex d. decrease if mitochondrial ADP is depleted e. be increased in active muscle, decreased in inactive muscle

a. All of the above

Explain why Coenzyme Q is an effective mobile electron carrier in the electron-transport chain. Select one or more: a. CoQ is able to move easily from the outside the mitochondrial membrane, across, and to the other side b. The 10 isoprene units render CoQ soluble in the hydrophobic environment of the inner mitochondrial membrane. c. The flexibility of the 10 isoprene units allows CoQ to interact with many different electron carriers d. The extended conjugation of the 10 isoprene units helps bridge the flow of electrons and light absorbing features of CoQ e. The two oxygen atoms can reversibly bind two electrons and two protons as the molecule transitions between the quinone and quinol forms Feedback

a. CoQ is able to move easily from the outside the mitochondrial membrane, across, and to the other side b. The 10 isoprene units render CoQ soluble in the hydrophobic environment of the inner mitochondrial membrane. d. The extended conjugation of the 10 isoprene units helps bridge the flow of electrons and light absorbing features of CoQ e. The two oxygen atoms can reversibly bind two electrons and two protons as the molecule transitions between the quinone and quinol forms Feedback

Which of the following statements about the chemiosmotic theory is correct? Select one: a. Electron transfer in mitochondria is accompanied by an asymmetric release of protons on one side of the inner mitochondrial membrane b. All of the above c. The effect of uncoupling reagents is a consequence of their ability to carry electrons through membranes d. It predicts that oxidative phosphorylation can occur, even in the absence of an intact inner mitochondrial membrance e. The membrane ATP synthase has no significant role in the chemiosmotic theory

a. Electron transfer in mitochondria is accompanied by an asymmetric release of protons on one side of the inner mitochondrial membrane

Which of the following enzymes would NOT be expected to contribute electron carriers to Oxidative Phosphorylation? Select one: a. Glucose 6-phosphate dehydrogenase b. Alcohol dehydrogenase c. Glyceraldehyde 3-phosphate dehydrogenase d. Succinate dehydrogenase e. Malate dehydrogenase

a. Glucose 6-phosphate dehydrogenase

Which of the following respiratory cascade complexes transfers electrons to or from coenzyme Q? Select one or more: a. Glycerol 3-phosphate dehydrogenase b. Complex III c. Complex IV d. Complex II e. Complex I

a. Glycerol 3-phosphate dehydrogenase b. Complex III d. Complex II e. Complex I

Molecular oxygen is normally 200-300 µM in the cytosol. Do you expect it to be present at higher or lower concentrations in membranes, and why? Select one: a. Higher, because it is a non-charged, non-polar molecule b. Higher, because most of the reactions involving oxygen occur in the membrane c. none of the above d. Lower, because various cytosolic proteins help stabilize the oxygen e. Lower, because water helps solubilize oxygen

a. Higher, because it is a non-charged, non-polar molecule

Which of the following electron carriers or prosthetic groups would not function after site-directed mutagenesis substituted Pro for Cys in succinate dehydrogenase? Select one: a. Iron-sulfur center b. Flavin adenine dinucleotide c. FMN d. Cytochrome C e. Ubiquinone

a. Iron-sulfur center

Which of the following are true of photosynthesis? Select one or more: a. NADP+ is reduced to NADPH via the light-dependent reactions b. Occurs only in plants c. ATP is synthesized via the light-dependent reactions d. The ratio of NADP and ADP consumed is a constant e. The light-dependent reactions also form trioses, hexoses and other carbohydrates

a. NADP+ is reduced to NADPH via the light-dependent reactions c. ATP is synthesized via the light-dependent reactions d. The ratio of NADP and ADP consumed is a constant

Given that ATP formation requires little energy by the synthase, what is the proton-motive force needed for? Select one: a. To release ATP from its binding site b. To allow ADP and Pi to bind initially c. To ensure that the charge separation remains intact d. None of the above

a. To release ATP from its binding site

ATP synthases isolated from different sources often have different numbers of C subunits. Would you expect that altering the number of C subunits will alter the yield of ATP as a function of proton flow? Select one: a. Yes, the subunit number determines number of protons needed to rotate the synthase 360 degrees; more subunits, more protons for a single turn, so fewer ATP per proton. b. No, the subunit number determines the number of protons needed to rotate the synthase 360 degrees, but this is unrelated to the number of ATP per proton c. No, the subunit number is unrelated to the number of protons needed to rotate the synthase 360 degrees d. None of the above e. Yes, the subunit number determines the number of protons needed to rotate the synthase 360 degrees; more subunits, more protons for a single turn, so more ATP per proton.

a. Yes, the subunit number determines number of protons needed to rotate the synthase 360 degrees; more subunits, more protons for a single turn, so fewer ATP per proton.

Rate the following electron acceptors based on their reduction potential. Greatest to lowest. Select one: a. NADP+ > Fd > A0 > PQa b. NADP+ > PQb >Fe-S > A0. c. NADPH > PQb >Fe-S > A0. d. Fd> A1> PQa> Ao

b. NADP+ > PQb >Fe-S > A0.

Which of the following statements about energy conservation in the mitochondrion is false? Select one: a. Uncouplers "short circuit" the proton gradient, thereby dissipating the proton motive force as heat b. Uncouplers (such as dinitrophenol) have exactly the same effect on electron transfer as inhibitors such as cyanide; both block further electron transfer to oxygen c. The yield of ATP per mole of oxidizable substrate depends on the substrate d. For oxidative phosphorylation to occur, it is essential to have a closed membranous structure with an inside and an outside e. Drugs that inhibit the ATP synthase will also inhibit the flow of electrons down the chain of carriers.

b. Uncouplers (such as dinitrophenol) have exactly the same effect on electron transfer as inhibitors such as cyanide; both block further electron transfer to oxygen

A spinach leaf has 20 micro grams /cm2 of chlorophyll a (mw 892) in an leaf. If each leaf has a surface area of 10 cm2 and can absorb 50% of radiation (with an energy of 5.4 J/ cm2 *min) hitting it. Given that the average lifetime of an excited chlorophyll molecule in vivo is 1 ns, what fraction of the chlorophyll molecules are excited at any one time? Select one: a. 100^8 molecules b. 2400 molecules c. 10^8 molecules d. 0.1^6 molecules

c. 10^8 molecules

The steady state concentrations of ATP, ADP and Pi in chloroplast while illuminated at pH 7.0 are 120, 6.0, 700 uM respectively. What is the delta G for the synthesis of 1 mol of ATP? Select one: a. 56 j/mol b. 7456 kilo watts/mol c. 56,000 j/mol d. -56 kj/mol

c. 56,000 j/mol

In the event that a hard working chlorophyll (a) cant preform a excition transfer what wavelength would if fluorescence at? Select one: a. 750- 790 nm b. Trick question, the emission from decay would undergo phospholuminescence and not a fluorescence pathway. c. 662-669 nM d. Do to the large extinction coefficient of chlorophyll a the electronic transition from the excited state down to the ground state is a forbidden transitions, allowing a electron acceptor to become available.

c. 662-669 nM

In normal mitochondria, the rate of NADH consumption (oxidation) will: Select one: a. decrease if mitochondrial ADP is depleted b. be very low if the ATP synthase is inhibited, but increase when an uncoupler is added. c. All of the above d. decrease when cyanide is used to prevent electron transfer through the cytochrome a + a3 complex e. be increased in active muscle, decreased in inactive muscle

c. All of the above

Which of the following statements is correct with respect to photosynthesis. Select one: a. Chlorophyll was "selected" by evolution as the dominate chromophore because it can maintain an electron in the excited state for >500 milliseconds, facilitating in electron transport to electron carriers. b. Chlorophyll can accept two distinct photons at longer wavelengths in order to promote an electron to the excited state. c. For a photon to be absorbed it must contain energy that matches the electronic transition. d. Light emission from an electron decaying to the ground state is also accompanied by exciton transfer.

c. For a photon to be absorbed it must contain energy that matches the electronic transition.

If you were to try and describe a phtosystem complex to a lay person you probably would create an appropriate analogy for a photosystem by using only one of the choices below. Select one: a. a pancake b. Mitochondria c. Radiodish d. Solar cell

c. Radiodish

What characteristic of chlorophyll does not contribute to photon absorption? Select one or more: a. An overall high molar extinction coefficient b. The polyene ring c. The coordination of Mg 2+ at the center d. The planarity of the pigments

c. The coordination of Mg 2+ at the center

How many electrons would enter Complex I from complete oxidation of Myristic Acid, 14:0? Select one: a. 42 b. 40 c. 18 d. 54 e. 52

d. 54

Which of the following is not a feature of complex IV? Select one: a. Oxygen is a substrate b. Copper is an essential metal for the reaction c. For every electron passed to complex IV, two protons are consumed from the matrix (N) side d. In order to generate two water molecules, complex IV must go through the catalytic cycle two times e. Cytochrome c is a one-electron donor

d. In order to generate two water molecules, complex IV must go through the catalytic cycle two times

In normal mitochondria, the rate of NADH consumption (oxidation) will: Select one: a. decrease when cyanide is used to prevent electron transfer through the cytochrome a + a3 complex b. be increased in active muscle, decreased in inactive muscle c. decrease if mitochondrial ADP is depleted d. be very low if the ATP synthase is inhibited, but increase when an uncoupler is added. e. All of the above

e. All of the above

You are carrying out experiments with purified and reconstituted cytosolic glycerol-3-phosphate dehydrogenase, which is "activated" at higher pH by changes in Km and Vmax (see chart). What control experiment best addresses whether placing the enzyme at the more acidic pH (7.0) causes the enzyme to become irreversibly inactivated? Select one: a. Carry out the experiment done in the chart, but go to more acidic pH's b. Carry out the previous experiments, but do replicates so you can get error bars c. Carry out the previous experiments but do intermediate pH values (e.g., 7.2, 7.4, 7.7, etc.) d. Isolate the enzyme from another source and repeat the experiment e. Preincubate the enzyme at pH 7.0 for varying lengths of time, assay for activity at pH 8.0.

e. Preincubate the enzyme at pH 7.0 for varying lengths of time, assay for activity at pH 8.0. *picture not included

During oxidative phosphorylation, the proton motive force that is generated by electron transport is used to: Select one: a. reduce O2 to H2O b. generate the substrates (ADP and Pi) for the ATP synthase c. create a pore in the inner mitochondrial membrane d. oxidize NADH to NAD+ e. induce a conformational change in the ATP synthase

e. induce a conformational change in the ATP synthase