Protein and Amino Acid Metabolism

Vocabulary flashcards covering protein digestion, absorption, metabolism, disorders, and nitrogen balance based on lecture notes.

Protein Metabolism

The digestion, absorption, synthesis, utilization, and breakdown of proteins within the body.

IgG

The most abundant type of antibody, found in all body fluids, which protects against bacterial and viral infections.

IgA

An antibody found in high concentrations in mucous membranes lining the respiratory passages and gastrointestinal tract, as well as in saliva and tears.

IgM

An antibody found mainly in blood and lymph fluid that is the first antibody made by the body to fight new infection.

IgE

An antibody associated mainly with allergic reactions to environmental antigens, found in the lungs, skin, and mucous membranes.

IgD

An antibody that exists in small amounts in the blood and is the least understood antibody.

Hydrochloric Acid (HCl)

Stomach acid that denatures proteins, activates pepsinogen into pepsin, and kills microorganisms.

Pepsin

A stomach enzyme activated from pepsinogen by hydrochloric acid that breaks proteins into smaller peptides.

Enteropeptidase

An enzyme that converts trypsinogen into trypsin in the small intestine.

Brush Border Enzymes

Enzymes located on intestinal microvilli, including aminopeptidase and dipeptidase, that complete protein digestion into free amino acids.

Thalassemia

An inherited blood disorder that causes the body to produce less hemoglobin than normal, leading to anemia and fatigue.

Type I Collagen

A fibril-forming collagen distributed in the skin, bone, tendon, blood vessels, and cornea.

Type II Collagen

A fibril-forming collagen distributed in cartilage, intervertebral disk, and vitreous body.

Type III Collagen

A fibril-forming collagen distributed in blood vessels and fetal skin.

Type IV Collagen

A network-forming collagen distributed in the basement membrane.

Type VII Collagen

A network-forming collagen distributed beneath stratified squamous epithelia.

Type IX Collagen

A fibril-associated collagen distributed in cartilage.

Type XII Collagen

A fibril-associated collagen distributed in tendons, ligaments, and some other tissues.

Osteogenesis Imperfecta

A heterogeneous group of inherited disorders known as brittle bone syndrome, distinguished by bones that easily bend and fracture.

Type I Osteogenesis Imperfecta

Also called osteogenesis imperfecta tarda; presents in early infancy with fractures secondary to minor trauma.

Type II Osteogenesis Imperfecta

Also called osteogenesis imperfecta congenita; the most severe form where patients die of pulmonary hypoplasia in utero or during the neonatal period.

Elastin

A connective tissue protein with rubber-like properties in tissues such as the lung.

Transamination

The transfer of an amino group from one amino acid to an $\alpha$-keto acid to form a new amino acid without releasing ammonia.

ALT (Alanine Aminotransferase)

An enzyme found primarily in the liver that serves as a specific marker of liver injury and requires vitamin B6 (pyridoxal phosphate) as a cofactor.

AST (Aspartate Aminotransferase)

An enzyme found in the liver, heart, skeletal muscles, kidneys, brain, and red blood cells that requires vitamin B6 (pyridoxal phosphate) as a cofactor.

Deamination

The removal of an amino group from an amino acid occurring mainly in the liver, producing toxic ammonia ($\text{NH}_3$) and a keto acid.

Urea Cycle

A biochemical pathway in the liver that converts toxic ammonia into urea to be excreted by the kidneys in urine.

Hyperammonemia

A clinical condition caused by liver failure where the liver cannot convert ammonia to urea, resulting in confusion, tremors, altered consciousness, hepatic encephalopathy, and coma.

Positive Nitrogen Balance

A state where $\text{Nitrogen intake} > \text{Nitrogen loss}$, occurring during growth, pregnancy, muscle building, and wound healing as the body builds tissue.

Negative Nitrogen Balance

A state where $\text{Nitrogen loss} > \text{Nitrogen intake}$, occurring during starvation, burns, trauma, cancer, infection, and protein deficiency as the body breaks down muscle.

Neutral Nitrogen Balance

A state where $\text{Nitrogen intake} = \text{Nitrogen loss}$, occurring in healthy adults.

Marasmus

A type of protein-energy malnutrition caused by a deficiency of both calories and protein, characterized by severe muscle wasting, thin extremities, no edema, and an old-man appearance.

Kwashiorkor

A type of protein-energy malnutrition caused by protein deficiency despite adequate calories, characterized by edema, enlarged fatty liver, distended abdomen, hair discoloration, and skin lesions.