Which substance is most abundant in a cell?

What type of bond exists between two water molecules?

The given structure represents a low molecular weight organic compound found in living tissues. Identify the category and the missing component $X$ in the structure.
Category $-$ Component

In which one of the following is nitrogen not a constituent?

When the body is rapidly oxidizing fat,excessive ketone bodies get accumulated in the body,resulting in the formation of

Vitamin $M$ is