Question

Which of the following amino acids has been solely regarded as a ketogenic amino acid?
(A). Threonine
(B). Tyrosine
(C). Phenylalanine
(D). Leucine

Answer 1

Basically a ketogenic amino acid is an amino acid that can be degraded directly into acetyl-$CoA$, which is the precursor of ketone bodies, especially during early development. Ketogenic amino acid serves important roles in the human body, it diets as possible treatment for non-alcoholic fatty liver disease and diabetes. Mainly, Ketogenic is a term for low-carb diet.

Complete step by step answer:
Basically the acetyl-$CoA$ , which is the ketone body which is formed by the degradation of ketogenic amino acids. Whereas glucogenic amino acids are converted into glucose. Ketogenic Amino acids are unable to be converted to glucose as both carbon atoms in the ketone body are ultimately degraded to carbon dioxide in the citric acid. Moreover, in humans, two ketogenic amino acids are Leucine and lysine. Furthermore, lysine and Leucine are ketogenic only and the remaining amino acids are solely glycogenic.
Threonine is both ketogenic and glucogenic because of acetaldehyde. This fact is completely ignored. It is an essential amino acid. The essential “amino acids” are those that cannot be made by the body and must be obtained from the diet.
Talking about tyrosine it cannot be synthesized by people, it becomes very essential. Thus, it is used by cells to synthesize proteins. This is a non-essential amino acid. Moreover, it is also synthesized by the body. The body employs a complex mechanism to regulate the amount of tyrosine in cells.
Phenylalanine is out of the amino acids which make up most proteins. Phenylalanine can cause intellectual disabilities, brain damage. Mostly, it occurs naturally in many proteins-rich foods such as milk eggs. It can increase a chemical in the body called tyro-mine.
Leucine, an essential amino acid, is one of the amino acids with a branched hydrocarbon side chain. It has one additional methylene group in its side chain compared with valise. Leucine is hydrophobic and generally buried in folded proteins. It is used in biosynthesis of proteins.

So, the correct answer is Option D.

Note:
Amino acids are organic compounds that contain amine and carboxyl functional groups, along with a side chain specific to each amino acid. Amino group is $- N{H_2}$ and carboxyl group is $- COOH$.