Metabolic Pathways of Energy Use

Polysaccharide Biosynthesis

Glycogen is formed from ADPG (ATP + glucose 6-phosphate = adenosine diphosphoglucose) in bacteria and from UDPG in animals (UTP + glucose 6-phosphate = uridine diphosphoglucose).

UDPNAc is the starting material for the biosynthesis of peptidoglycan (UTP + fructose 6-phosphate = UDP-N-acetylglucosamine).

Lipid Biosynthesis

Lipids are synthesized form fatty acid and glycerol.

Glycerol is derived from dihydroxyacetone phosphate, and fatty acids are built from acetyl CoA.

Amino Acid and Protein Biosynthesis

Amino acids are required for protein biosynthesis.

All amino acids can be synthesized either directly or indirectly from intermediates of carbohydrate metabolism, particularly from the Krebs cycle.

Transamination or amination reactions: Organic acids + an amine group = amino acid.

Not all organisms can do this.  Some require preformed amino acids.

Purine and Pyrimidine Biosynthesis

The sugars composing nucleotides are derived from either the pentose phosphate pathway or the Entner-Doudoroff pathway.

Carbon and nitrogen atoms from certain amino acids (aspartic acid, glycine, glutamic acid) form the backbones of the purines and pyrimidines.

Includes DNA, RNA, ATP, NAD, NADP, FMN, and FAD.

The Integration of Metabolism

Anabolic and catabolic reactions are integrated through a group of common intermediates.

Such integrated metabolic pathways are referred to as amphibolic pathways.