Final answer:
Nitrous acid replaces amino groups with keto groups through a process called oxidative deamination, in which an amino group is converted into an a-keto acid and an ammonium ion. The correct term for this process is deamination.
Step-by-step explanation:
Nitrous acid is known to cause deamination, which is the replacement of an amino group (-NH2) with a keto group (=O), resulting in the formation of an a-keto acid. This process is part of oxidative deamination, an important metabolic reaction that takes place in the mitochondria. During oxidative deamination, an amino acid loses its amino group in the form of an ammonium ion (NH4+), and the amino acid is converted back into an a-keto acid. Oxidative deamination involves the reduction of NAD+ to NADH, which subsequently enters the oxidative phosphorylation pathway to produce ATP. The other byproduct of this process, ammonium (NH4+), is a toxic substance that is usually processed through the urea cycle to be eliminated from the body.
In the context of the question asked, the correct answer for the process in which nitrous acid replaces amino groups with keto groups is B. deamination.