In the case of carbohydrates, this refers to their
relation with a particular isomer of glyceraldehyde Glyceraldehyde
contains one asymmetric carbon atom and exists in two enantiomeric
forms as shown below (+) Isomer of glyceraldehyde has ‘D’ configuration It means that when
its structural formula is written on paper following specific conventions
which you will study in higher classes, the –OH group lies on right hand
side in the structure