Question

Which of the following compounds is not a vitamin?
(A) niacin
(B) riboflavin
(C) thiamine
(D) guanine

Answer 1

A vitamin is an organic substance that is an important micronutrient that an organism needs in tiny amounts for its metabolism to function properly. Essential nutrients are unable to be produced in the body, either entirely or in adequate amounts, and must therefore be acquired via the food.

Complete Step By Step Answer:
Nucleobases, also known as nitrogenous bases or just bases, are nitrogen-containing biological molecules that create nucleosides, which are components of nucleotides, and all of these monomers make up the nucleic acid's fundamental building blocks. Nucleobases' capacity to create base pairs and stack them on top of one another leads to long-chain helical structures like ribonucleic acid (RNA) and deoxyribonucleic acid (DNA).
The fundamental or canonical nucleobases are adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U). The nucleotides A, G, C, and T are present in DNA, whereas A, G, C, and U are found in RNA. They serve as the basic components of the genetic code.
Niacin, commonly known as nicotinic acid, is an organic molecule and a kind of vitamin ${{B}_{3}}$ that is necessary for human health. Plants and animals may produce it from the amino acid tryptophan.
Vitamin ${{B}_{2}}$ , commonly known as riboflavin, is a food-based vitamin that may also be taken as a nutritional supplement. The body needs it for cellular respiration.
Thiamine, often called thiamine or vitamin ${{B}_{1}}$ , is a vitamin that can be found in foods and is also available as a dietary supplement and medicine. Whole grains, beans, and certain meats and seafood are all good sources of thiamine.
Hence option D is correct.

Note:
Guanine is one of the four major nucleobases found in DNA and RNA. The others are adenine, cytosine, and thymine (uracil in RNA). Guanine is linked with cytosine in DNA. Guanosine is the name for the guanine nucleoside. Guanine is a purine derivative with the formula ${{C}_{5}}{{H}_{5}}{{N}_{5}}O$ , consisting of a fused pyrimidine-imidazole ring structure with conjugated double bonds. The bicyclic molecule is planar because of its unsaturated configuration.