Biosynthesis of many molecules in cells, and many modifications of macromolecules like proteins, RNA, and DNA require addition of single carbons. What is/are the major carrier/s of single carbons in cells?

a) S-adenosylmethionine

b) Acetyl CoA

c) Tetrahydrofolate

d) a and b

e) a and c

The correct answer is option e) "a and c".

Explanation:

Single carbons are atoms needed for the biosynthesis of many molecules in cells, therefore the cells need a pathway to move group of atoms containing single carbons to make them available for the biosynthesis. S-adenosylmethionine and Tetrahydrofolate are two of the major carriers of single carbons in cells. S-adenosylmethionine (SAM) acts as a methyl (-CH3) donor and Tetrahydrofolate (THF) as a cofactor in enzymatic reactions.