21.

Choose the correct statement from the following:

• Disulfide bonds in a 20-residue peptide can be formed only if the cysteines are adjacent to each other.

• The amino acid isoleucine has only one chiral centre.

• Both bases and sugar contribute to the chirality of nucleic acids.

• The pI of aspartic acid is less than that of glutamic acid.

Indicate the INCORRECT statement from the following:

• Allosteric enzymes function through reversible noncovalent binding of allosteric modulators or effectors.

• Monoclonal antibodies that catalyze the hydrolysis of esters or carbonates can be produced.

• Enzymes are not inhibited irreversibly by heavy metals such as Hg²⁺, Ag⁺.

• Acid phosphates hydrolyze biological phosphate esters at ∼ pH 5.0

What is the effect of sudden increase in the levels of ATP and citrate on an erythrocyte undergoing glycolysis?

• It inhibits glycolysis.

• It stimulates glycolysis.

• The rate of glycolysis remains unaltered.

• The rate of glycolysis increases gradually.

The φ and ψ of a β-strand composed of all D-amino acids will mainly occupy which quadrant in the Ramachandran plot?

• upper left

• upper right

• lower left

• lower right

In a signalling event, binding of an extracellular ligand activates G-protein coupled receptor (GPCR) that eventually activates phospholipase C-β. Which one of the following statements truly reflects the function of phospholipase C-β?

• Phospholipase C-β converts PI (3, 4, 5)P₃ to PI (4, 5)P₂.

• Phospholipase C-β converts PI (4)P to PI (4, 5)P₂.

• Phospholipase C-β converts PI (4, 5)P₂ to diacylglycerol and IP₃.

• Phospholipase C-β converts PI (5) to PI (4, 5)P₂.

Select a cellular body which is NOT a part of the nuclear bodies:

• P bodies

• Nucleolus

• Cajal bodies

• Interchromatin granule clusters

Which one of the following statements about chromatin is NOT true?

• DNA winds approximately 1.65 times around the nucleosomes.

• H2A-H2B binds to both the entry and exit ends of DNA in nucleosomes.

• Covalent modification of histones influence chromatin compaction.

• Non-histone proteins are part of mitotic chromosomes.

During eukaryotic cell division, metaphase to anaphase transition is regulated by degradation of

• Cyclin B1

• CDK1

• Aurora A kinase

• Polo-like kinase

One of the mechanisms used by bacteria for adaptation to changed environment is altering the transcription of their genes. In this regard, which one of the following responses is NOT found in bacteria?

• A gene with two different promoters for expression in different conditions.

• use of different sigma factors for transcription of genes.

• Expression of alternate α, β and β' subunits.

• Expression of anti-sigma factors.

Which one of the following λ proteins acts both as an activator and repressor of transcription?

• cI protein

• N protein

• cII protein

• Q protein