Electron transport chain and oxidative phosphorylation- MCQs (Set-2)

Q.1- If the mitochondria were blocked at the site of NADH oxidation and were treated with succinate as substrate, what would the P: O ratio is?

A. Zero

B. One less than normally produced by succinate

C. Same as that normally produced by succinate

D. One more than normally produced by succinate

E. Higher than normal because of the excessive heat produced from uncoupling

Q.2- If the oxidative phosphorylation was uncoupled in the mitochondria, what would one expect?

A. A decreased concentration of ADP in the mitochondria

B. Increased inorganic phosphate in the mitochondria

C. A decreased oxidative rate

D. A decreased production of heat

E. Increased transport of ADP from the cytosol to the mitochondrial matrix

Q.3- If the rotenone is added to the mitochondrial electron transport chain:

A. P: O ratio of NADH is reduced from 3:1 to 2:1

B. Rate of NADH oxidation is diminished to two- thirds of its initial value

C. Succinate oxidation remains normal

D. Oxidative phosphorylation is uncoupled at the site I

E. Electron flow is inhibited at site II

Q.4- If 2, 4 dinitrophenol is added to tightly coupled mitochondria that are actively oxidizing succinate:

A. Electron flow will continue but ATP synthesis will not occur

B. Electron flow will continue but ATP synthesis will be increased

C. Electron flow will cease, but ATP synthesis will continue

D. Both Electron flow and ATP synthesis will be ceased

E. Subsequent addition of Oligomycin will cause ATP hydrolysis

Q.5- The prosthetic group of NADH dehydrogenase:

A. FMN

B. NADH

C. FAD

D. NADPH

E. Iron

Q.6- In substrate-level phosphorylation

A. The substrate reacts to form a product containing a high energy bond

B. ATP synthesis is linked to the dissipation of the proton gradient

C. High energy intermediate compounds cannot be isolated

D. Oxidation of one molecule of substrate is linked to the synthesis of more than one ATP molecule

E. Only mitochondrial reactions participate in ATP formation

Q.7- The chemiosmotic hypothesis involves all of the following except

A. A membrane impermeable to protons

B. Electron transport by the respiratory chain pumps protons out of the mitochondria

C. Proton flow into the mitochondria depends on the presence of ADP and Pi

D. ATPase activity is reversible

E. Only proton transport is strictly regulated, other positively charged ions can diffuse freely across the mitochondrial membrane

Q.8- The effect of Valinomycin on oxidative phosphorylation involves all of the following except-

A. The net yield of ATP decreases

B. Rate of oxygen consumption increases

C.  Excessive heat is released

D. pH gradient across the inner mitochondrial membrane decreases

E. The rate of flow of electrons increases

Q.9- Which of the following ETC components accept only one electron?

A. Coenzyme Q

B. Cytochrome b

C. FAD

D.FMN

E. O₂

Q.10- Which of the following has the highest redox potential in the respiratory chain?

A. O2

B. Ubiquinone

C. NAD

D.FMN

E. FAD

Key to answers

1)-C, 2)-B, 3)-C, 4)-A, 5)-A, 6)-A, 7)-E, 8)-D, 9) – B, 10)-A.