Question

What is a synthesis reaction called in biology

Answer 1

It's called biosynthesis.

Another name could be anabolism.

Biosynthesis is a process in which substrates are converted into more complex products with the help of enzymes.
Substrate + Substrate ----(enzyme)---------> Product

Unlike chemical synthesis, biosynthesis occurs within living organisms and is a vital part of metabolism pathways.

Answer 2

A synthesis reaction in biology is a compound