Which one of the following non-covalent interactions between two non-bonded atoms A and B is most sensitive to the distance between them?

• A and B are permanent dipoles and are involved in hydrogen bonding

• A and B are fully ionized and are involved in salt bridge formation

• A and B are uncharged and repel each other.

•  A and B are uncharged and attract each other

The gel to liquid crystalline transition temperature (T_m) of phospholipids is dependent on the fatty acid composition. Considering this, T_m of

• all the phospholipids will be identical

• DPPC will be lowest and DOPC will be highest.

• POPC and DOPC will be identical and lower than DMPC or DPPC

• DOPC will be lowest and DPPC will be highest.

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.

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.

Which statement best describes the pKa of amino groups in proteins?

• pKa of the α-amino group is higher than the pKa of ε- amino group.

• pKa of the α-amino group is lower than the pKa of ε- amino group.

• pKa of the α-amino group is the same as the pKa of ε- amino group.

• pKa of the α-amino group is higher than the pKa of the guanidine side chain of arginine.

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.

A protein has 30% alanine. If all the alanines are replaced by glycines.

• helical content will increase

• β-sheet content will increase

• there will be no change in conformation

• the alanine-substituted protein will be less structured than the parent protein

Origin of replication usually contains

• GC rich sequences

• Both AT and GC rich sequences

• No particular stretch of sequences

• AT rich sequences

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.

σ-subunit of E. coli RNA Polymerase DOES NOT

• initiate transcription and fall off during elongation.

• increase affinity of the core enzyme to the promoter

• binds to DNA, independent of the core enzyme

• ensures specificity of transcription by interacting with the core enzyme