What is the effect of 2, 4-dinitrophenol on mitochondria?

• Blocks ATP synthesis without inhibiting electron transport by dissipating the proton gradient.

• Blocks electron transport and ATP synthesis by inhibiting ATP-ADP exchange across the inner mitochondrial membrane.

• Blocks electron transport and proton pumping at complexes I, II and III

• interacts directly with ATP synthase and inhibits its activity.

42.

You have created a fusion between the top operon, which encodes the enzymes for tryptophan biosynthesis, under the regulatory control of the lac operator. Under which of the following conditions will tryptophan synthase be induced in the strain that carries the chimeric operator fused operons?

• only when both lactose and glucose are absent

• only when lactose is absent and glucose are present

• only when lactose is absent and glucose is present

• only when lactose is present and glucose is absent.

Which of the following pairs of subcellular compartments is likely to have the same pH and electrolyte composition?

• cytosol and lysosomes

• cytosol and mitochondrial intermembrane space

• cytosol and endosome

• mitochondrial matrix and intermembrane space.

Regarding microtubule assembly and disassembly during cell division, which will be the most appropriate answer?

• Once formed, kinetochore microtubules depolymerize at the plus ends throughout mitosis.

• Once formed, kinetochore microtubules polymerize at the plus ends throughout mitosis.

• Kinetochore microtubules polymerize at their plus ends up to anaphase, at which point they begin to depolymerize.

• Kinetochore microtubules polymerize at their minus ends up to cytokinesis, at which point they depolymerize.

What would be the outcome if the theca interna cells were destroyed in a Graafian follicle?

• Immediate formation of corpus albicans.

• Increased progesterone synthesis in the granulosa cells.

• Decreased estrogen synthesis in the granulosa cells

• Formation of corpus hemorrhagicum.

You are following the intracellular sorting of an integral plasma membrane protein in a living cell, in culture. You have decided to probe this protein by metabolic labeling technique with ³⁵S-methionine (pulse-chase-technique). After one cycle of division, the cells were treated with a potent inhibitor of protein biosynthesis and processed for subcellular fractionation. In which of the following fractions will you expect the presence of this protein upon immunoprecipitation with a specific antibody?

• only cytoplasm

• Only plasma membrane

• Both endoplasmic reticulum and plasma membrane

• Only secretory vesicles and endoplasmic reticulum.

The principal pathway for transport of lysosomal hydrolases from the trans-Golgi network (pH 6.6) to the late endosomes (pH 6.0) and the recycling of M6P (mannose 6 phosphate) receptors back to the Golgi depends on thee pH difference between those compartments. From what you know about M6P receptor binding and recycling and the pathways for delivery of material to lysosomes, predict what would happen if the pH in late endosomes was raised to 6.6?

• M6P will bind to hydrolases but will not release the hydrolases in the late endosomes.

• M6P will bind to hydrolases and will release the hydrolases in the late endosomes.

• At higher endosomal pH, the receptor would not release the hydrolase and could not be recycled back to the trans-Golgi network.

• M6P will be degraded at higher pH

A rapidly growing bacterial species such as E.coli exhibits a typical phase of the growth cycle in liquid nutrient broth (lag phase → log phase → stationary phase → death phase). If a bacterial culture has a starting density of 10³ cells/ ml has a lag time of 10 minutes and a generation time of 10 minutes, what will be the cell density be at (cells/ml) 30 minutes?

• 6.0 × 10³

• 2.0 × 10³

• 3.0 × 10³

• 4.0 × 10³

According to the current model of alternative oxidase regulation, the following factors cause induction of alternative oxidase:

(A) significant increase in the ubiquitin pool in the cytosol.

(B) presence of α-keto acids (like pyruvate and glyoxylate).

(C) cold stress.

(D) increase in cytosolic ATP concentration.

Which one of the following combinations of above statement is true?

• (A) and (D)

• (B) and (C)

• (A) and (B)

• (A) and (C)

Amoebae are known to double in 3 min. Two identical vessels A and B, respectively contain one and two amoebas to start with. The vessel B gets filled in 3 hours. When will A get filled?

• 3 hours

• 2 hours 57 min

• 3 hours 3 min

• 6 hours