Practice Questions

A glycosidic bond is the covalent linkage that joins monosaccharides into polysaccharides. A peptide bond is the analogous covalent linkage that joins amino acids into polypeptide chains. Both are formed by dehydration synthesis and create the primary polymer backbone.

Some proteins can refold spontaneously into their native, biologically active conformation after the denaturing agent is gently removed. This is called renaturation. This ability indicates that the primary sequence remains intact and contains all the information for folding.

Aspirin (acetylsalicylic acid) acts by transferring its acetyl group to a serine hydroxyl in the active site of COX enzymes. This chemical modification is covalent and permanent (for the life of the enzyme), making it an irreversible inhibition, not a reversible binding interaction.

The cis-double bond introduces a fixed bend in the hydrocarbon tail. This prevents the fatty acid chains from packing closely together, increasing the free volume within the bilayer and thereby increasing its fluidity and permeability compared to saturated chains.

The amino acid is covalently attached to the 3' acceptor stem of its cognate tRNA molecule. During elongation, the peptidyl transferase center of the ribosome catalyzes the nucleophilic attack of the amino group of the incoming aminoacyl-tRNA on the ester bond of the peptidyl-tRNA.

Adipose tissue, rich in triglycerides, serves as a padding that protects vital organs from physical shock. It also functions as a thermal insulator in subdermal layers, reducing heat loss from the body. Energy storage is its primary role, but the options highlight these secondary roles.

According to Chargaff's rules, if C = 30%, then G = 30%. Total C+G = 60%. The remaining 40% is A+T, so A = 20% and T = 20%.

A missense mutation is a single nucleotide change that results in a codon for a different amino acid. Here, arginine is replaced by alanine, which will likely alter the protein's primary structure and potentially its function. A silent mutation codes for the same amino acid.

Enzymes, like all catalysts, speed up the rate of a reaction by providing an alternative pathway with a lower activation energy (Ea). They do not change the overall free energy change (ΔG) or the equilibrium constant of the reaction. Without this rate enhancement, metabolic reactions would be too slow to sustain life.

Inorganic ions, like Mg²⁺, Zn²⁺, or Fe²⁺, that bind loosely to an enzyme and increase its activity are termed activators or inorganic cofactors. A coenzyme is an organic molecule. A prosthetic group is a tightly-bound organic or inorganic molecule.