Protein Metabolism Lecture 08

Vocabulary flashcards covering the formation and fate of the amino acid pool, nitrogen balance types, and the specific physiological functions of various amino acids and their derivatives.

Amino Acid Pool

Free amino acids present throughout the body in both intra and extracellular fluids, totaling approximately $90 - 100\,g$.

Nitrogen Balance

The difference between total nitrogen intake and total nitrogen loss in feces, urine, and perspiration over a certain length of time.

Nitrogen Equilibrium

A state where nitrogen intake matches nitrogen output.

Positive Nitrogen Balance

A condition where nitrogen excretion is less than nitrogen intake, occurring during growth, pregnancy, and convalescence from wasting illness.

Negative Nitrogen Balance

A condition where nitrogen excretion is greater than nitrogen intake, observed in starvation, fevers, burns, and wasting diseases.

Biogenic Amines

Basic nitrogenous compounds formed mainly by the decarboxylation of amino acids, including histamine, serotonin, and catecholamines.

Histamine

An excitatory neurotransmitter formed from Histidine via decarboxylation that regulates gastric $HCl$ secretion and is associated with allergic reactions.

Serotonin (5-HT)

A neurotransmitter synthesized from Tryptophan that regulates mood, appetite, sleep, and cognitive functions while acting as a vasoconstrictor.

Hartnup Disease

A condition caused by impaired intestinal and renal transport of neutral amino acids including Tryptophan, resulting in massive aminoaciduria and pellagra-like symptoms.

Glycine

An amino acid that serves as a precursor for heme, purines, glutathione, and creatine, and acts as an inhibitory neurotransmitter in the brain.

Creatine

A nitrogen-containing compound synthesized from glycine, arginine, and a methyl group from SAM; $95\%$ is present in skeletal muscle.

Phosphocreatine

Formed by the reversible phosphorylation of creatine by creatine kinase (CK), used to maintain intracellular $ATP$ levels during intense muscular contraction.

CKMB isozyme

A specific isozyme of creatine kinase whose presence in plasma is used for the diagnosis of myocardial infarction.

Creatinine

A waste product formed by the spontaneous cyclization of creatine and creatine phosphate, excreted in urine at a rate proportional to total muscle mass.

Serum Creatinine

A clinical marker used to assess renal function and Glomerular filtration rate (GFR); levels increase in acute kidney injury or chronic kidney disease.

Cysteine

An amino acid required for the biosynthesis of Coenzyme-A (CoA).

Serine

An amino acid involved in the synthesis of purines, pyrimidines, sphingosines, and the formation of cystathionine during methionine metabolism.

Glutamic acid

An excitatory neurotransmitter and precursor for glutathione, glutamine, and Gamma amino butyric acid (GABA).

Gamma amino butyric acid (GABA)

An inhibitory neurotransmitter synthesized from Glutamic acid.

Nitric Oxide (NO)

A potent smooth muscle relaxant, neurotransmitter, and vasodilator synthesized from Arginine by calcium-dependent NO synthase.

Tyrosine

A precursor amino acid for the synthesis of catecholamines (Dopamine, Nor Epinephrine, Epinephrine), melanin, thyroid hormone, and tyramine.

Tyramine

A substance formed by the decarboxylation of tyrosine, found in cheese, which helps regulate blood pressure.