The bond angle between $H-O-H$ in a water molecule is ......... (in $^o$)

The vitamin theory was proposed by:

$X$ - Glycosidic bond is formed by dehydration.
$Y$ - Due to hydrolases,peptide bond splits.

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

The energy available for the work of a biological system is known as.....

Water is generally found in liquid form because ........