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Amino Acid Biosynthetic Pathways01:29

Amino Acid Biosynthetic Pathways

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...
Amino acids03:42

Amino acids

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...
Keto–Enol Tautomerism: Mechanism01:14

Keto–Enol Tautomerism: Mechanism

The keto and enol forms are known as tautomers and they constantly interconvert (or tautomerize) between the two forms under acid or base catalyzed conditions. Both the reactions involve the same steps—protonation and deprotonation— although in the reverse order.
Tail-anchoring of Proteins in the ER Membrane01:45

Tail-anchoring of Proteins in the ER Membrane

Tail-anchored, or TA, proteins are estimated to make up to 3-5% of membrane proteins found in the eukaryotic cell. Such proteins have a single transmembrane domain located approximately 30 amino acid residues upstream from the C-terminal end. As a result, the signal recognition particle (SRP) cannot guide a TA protein to the ER membrane for cotranslational insertion. Hence, they are integrated into the ER membrane post-translationally using their C-terminal end as the anchor. TA proteins...
Nomenclature of Secondary and Tertiary Amines01:12

Nomenclature of Secondary and Tertiary Amines

The secondary and tertiary amines are derivatives of ammonia, where two and three of its hydrogens are replaced by alkyl groups, respectively. Secondary and tertiary amines can be symmetrical with identical alkyl groups attached to the nitrogen atom or unsymmetrical when more than one type of alkyl group is present. The standard nomenclature of secondary and tertiary amines is similar to the names given to the primary amines. They are generally named alkylamines. As depicted in Figure 1, for...
Amino Acid Catabolism01:18

Amino Acid Catabolism

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...