Chapter 15, Problem 1RQ

Summary Introduction

To review:

The sources of substrate for biosynthesis and the types of pathways that form these substrates.

Introduction:

Biosynthesis is a multistep process that is catalyzed by enzymes where substrates in a living organism are converted into more complex products. In this process, simple compounds get modified or transform into another compound or bound together to form macromolecules. It helps in building a carbon skeleton by reversing pathways such as TCA (Tricarboxylic acid cycle) which then incorporates nitrogen from amino acids.

Explanation of Solution

Microbes obtain an organic substrate such as acetyl CoA from minerals like carbonate and nitrate for biosynthesis. Biosynthesis requires nitrogen, oxygen, carbon, hydrogen, and other essential elements. Carbon is procured by affixing CO2 (carbon dioxide) or by acquiring other organic molecules. Biosynthesis generally reduces substrates through hydrogenation and oxygen removal. Cell components like amino acids and lipids are reduced more than substrates like acetate and CO2.

Biosynthesis often requires metabolic pathways. Some of these biosynthetic pathways are within single-celled organelles while others contain enzymes inside several cell organelles. Examples of such biosynthetic pathways include the production of components for the lipid membrane and nucleotides. Biosynthesis is an energy-demanding process. Chemical energy can be found in the form of molecules with high energy.