Struttura e Classificazione degli Aminoacidi

Study Notes

Amino Acid Structure and Classification

Amino acids are organic compounds containing both an amino group (-NH₂) and a carboxyl group (-COOH).
The general structure of an amino acid includes a central α-carbon atom bonded to the amino group, carboxyl group, a hydrogen atom, and a variable side chain (R group).
The R group differentiates the 20 standard amino acids found in proteins.
Classification of amino acids is based on the properties of their side chains:
- Nonpolar, aliphatic side chains: Glycine, Alanine, Valine, Leucine, Isoleucine, Methionine, Proline
- Aromatic side chains: Phenylalanine, Tyrosine, Tryptophan
- Polar, uncharged side chains: Serine, Threonine, Cysteine, Asparagine, Glutamine
- Polar, charged side chains (acidic): Aspartic acid, Glutamic acid
- Polar, charged side chains (basic): Lysine, Arginine, Histidine

Amino Acid Properties

Solubility: Amino acids with polar or charged side chains are more soluble in water than those with nonpolar side chains.
Acid-Base properties: Amino acids are amphoteric, meaning they can act as both acids and bases. At a specific pH, called the isoelectric point (pI), the amino acid exists predominantly as a zwitterion (a dipolar ion with both positive and negative charges).
Stereochemistry: All amino acids, except glycine, exist as stereoisomers (L and D forms) due to the presence of a chiral α-carbon atom. Only the L-amino acids are commonly found in proteins.
Optical activity: L-amino acids are levorotatory (rotate polarized light to the left).

Essential and Nonessential Amino Acids

Essential amino acids cannot be synthesized by the human body and must be obtained from the diet.
Nonessential amino acids can be synthesized by the human body.

Amino Acid Functions

Protein synthesis: Amino acids are the building blocks of proteins.
Enzyme catalysis: Many enzymes are proteins composed of amino acids, which catalyze biochemical reactions.
Hormone synthesis: Some hormones, such as insulin and glucagon, are composed of amino acids.
Neurotransmitter synthesis: Amino acids like tyrosine are precursors for the synthesis of catecholamine neurotransmitters (e.g., dopamine, norepinephrine).
Transporters: Amino acids can be components of transport systems throughout the body.
Energy source: When dietary intake and stored glycogen are depleted, amino acids can be catabolized to provide energy.

Biochemical Reactions

Peptide bond formation: Condensation reaction between the carboxyl group of one amino acid and the amino group of another amino acid, eliminating a water molecule.
Hydrolysis: Breakdown of peptide bonds by the addition of water, often facilitated by enzymes (proteases).
Amino acid metabolism: Conversion of amino acids into other molecules or into energy.

Amino Acid Metabolism

Deamination: Removal of the amino group from an amino acid, often through oxidative deamination. This produces ammonia (toxic), which is then converted to urea for excretion.
Transamination: Transfer of an amino group from one amino acid to a keto acid, forming a new amino acid and a new keto acid. This process helps to interconvert amino acids and maintain metabolic balance.
Amino acid catabolism: Breakdown of amino acids for energy generation or to produce other essential molecules.

Clinical Significance

Nutritional deficiency: An inadequate intake of essential amino acids can lead to protein deficiency and various health problems.
Inborn errors of amino acid metabolism: Genetic defects in enzymes involved in amino acid metabolism can cause accumulation of toxic metabolites, leading to various metabolic disorders.
Amino acid imbalance: Disruptions in the balance of amino acid concentrations can contribute to diseases like diabetes, certain types of cancer and heart disease.
Amino acid supplements: These can be used to treat specific conditions or as part of dietary regimes. Individual requirements should be carefully evaluated and monitored.

Description

Questo quiz esplora la struttura chimica e la classificazione degli amminoacidi. Gli amminoacidi sono composti organici essenziali per la vita e la loro classificazione si basa sulle proprietà delle loro catene laterali. Scopri di più sui diversi gruppi di aminoacidi e le loro caratteristiche uniche.