Question

(b) After the newly formed protein leaves the ribosome the first amino acid in the protein, methionine, is removed. What specific type of enzyme catalyzes this reaction?

(c) When benzo[a]pyrene is formed in the burning of meat. What substance(s) in the meat is the source of the aromatic rings in the product?

(d) How do drug manufacturers make most drugs water soluble?

(e) What is the name of the reaction that would convert a RNA nucleoside into a DNA nucleoside?

Answer 1

Answers :

(b) Methionine is co-translationally removed by the enzyme methionine aminopeptidase.

(c) On heating meat, like in grilling, due to incomplete combustion, benzo[a]pyrene is formed. Benzo[a]pyrene is Polycyclic Aromatic Hydrocarbon (PAH's) which is formed by multiple benzene rings. PAH along with Heterocyclic amines (HCA's) in heated meat are source of aromatic rings. These compounds are carcinogenic.

(d) The solubility of a drug is related to the particle size of a drug. Therefore, Drug manufacturers make the drug water soluble by reducing the particle size. This reduction in size cause the surface area to increase which in turn allows for more interaction with the solvent thereby increasing solubility. Other ways in which Solubility is increased are Solid-dispersion and use of surfactants.

(e) RNA contains Ribose sugar whereas DNA contains deoxyribose. The reaction required to convert RNA nucleoside to DNA nucleoside is deoxygenation (Removal of oxygen). The enzyme that is responsible for this conversion is ribonucleotide reductase. It catalyses the deoxygenation process.