Biochemistry

Step 1: Understand gel filtration (Sephadex G-200) principle.
Gel filtration chromatography separates proteins based on size — larger molecules elute first as they bypass the pores, while smaller molecules enter the pores and elute later. Given elution order:
A (first) → largest protein
D (last) → smallest protein
Step 2: Understand SDS-PAGE principle.
SDS-PAGE separates proteins based on molecular weight in a denatured state. SDS imparts a uniform negative charge, so proteins move according to size — smaller proteins migrate faster, and larger proteins move slower (i.e., have minimum electrophoretic mobility).
Step 3: Analyze both techniques.
Since protein A elutes first in Sephadex G-200, it is the largest. Hence, in SDS-PAGE, it will move the least (minimum mobility).

Step 1: Understand N-linked glycosylation.
N-linked glycosylation is a common post-translational modification in which a carbohydrate (glycan) is attached to the nitrogen atom in the side chain of a specific amino acid.
Step 2: Identify the target amino acid.
In N-linked glycosylation, the carbohydrate is attached to the amide nitrogen of the asparagine residue within a specific consensus sequence (Asn-X-Ser/Thr, where X is any amino acid except proline).
Step 3: Eliminate incorrect options.
Valine does not participate in glycosylation.
Serine and Threonine are involved in O-linked glycosylation (attachment to hydroxyl group).
Asparagine is the correct residue for N-linked glycosylation.

Step 1: Understanding enzyme catalysis.
Enzymes lower the activation energy of both forward and reverse reactions, facilitating the establishment of equilibrium. They do not alter the position of equilibrium but speed up the attainment of it.
Step 2: Analyze the options.
Option (1) is correct: Reversible enzyme-catalyzed reactions reach equilibrium after some time.
Option (2) is correct: Removing the product shifts the equilibrium, influencing the direction of the reaction (Le Chatelier’s Principle).
Option (3) is correct: Enzymatic activity depends on both temperature and concentration.
Option (4) is incorrect: The forward and reverse reactions proceed via the same transition state (activation complex), not different ones.
Therefore, statement (4) is NOT correct.