Amino acids are the monomers that comprise proteins. Each amino acid has the same fundamental structure, which consists of a central carbon atom, or the alpha (α) carbon, bonded to an amino group (NH2), a carboxyl group (COOH), and to a hydrogen atom. Every amino acid also has another atom or group of atoms bonded to the central atom known as the R group. There are 20 common amino acids present in proteins, each with a different R group. Variation in the amino acid sequence is responsible for...

Amino acid biosynthesis is essential for cell growth, protein synthesis, and metabolic regulation. Cells generate essential and non-essential amino acids from metabolic intermediates to sustain vital biological functions. These intermediates originate from key metabolic pathways: glycolysis, the tricarboxylic acid (TCA) cycle, and the pentose phosphate pathway. Important precursors include α-ketoglutarate, pyruvate, oxaloacetate, phosphoenolpyruvate, and erythrose-4-phosphate, which provide...

Proteins are polymers of amino acids linked together by peptide bonds. Proteins and polypeptides are interchangeably used to refer to long chains of amino acids. However, polypeptides have a molecular weight of fewer than 10,000 daltons, while proteins have greater molecular weight.  Polypeptides with less than 20 amino acids are called oligopeptides or simply peptides. Interactions among the constituent amino acid side chains of proteins help them fold into a stable 3-dimensional structure...

Overview

Microorganisms rely on proteins as an essential carbon and energy source, particularly in environments with limited polysaccharides or lipids. However, proteins are too large to cross the plasma membrane unaided, necessitating enzymatic degradation. Microbes secrete extracellular proteases and peptidases that hydrolyze proteins into peptides, which can then be transported across the membrane. Once inside the cell, intracellular proteases degrade these peptides into free amino acids, which...

Heterocyclic amines, where the N atom is a part of an alicyclic system, are similar in basicity to alkylamines. Interestingly, the heterocyclic amine having a nitrogen atom as part of an aromatic ring has much less basicity than its corresponding alicyclic counterpart. For this reason, as presented in Figure 1, piperidine (pKb = 2.8) is significantly more basic than pyridine (pKb = 8.8).