Protein Physiology And Analysis Flashcards
What are the main enzymes involved in protein digestion?
Pepsin (stomach), Trypsin, Chymotrypsin, Carboxypeptidase (pancreas), and Aminopeptidase (intestine).
How are amino acids absorbed in the intestine?
Via sodium-dependent active transport in enterocytes and transported to the liver via the portal vein.
What are the essential amino acids?
Valine, Leucine, Isoleucine, Methionine, Threonine, Lysine, Phenylalanine, Tryptophan (+Histidine and Arginine in children).
What happens to amino acids after absorption?
Used for protein synthesis, energy production, gluconeogenesis, ketogenesis, or nitrogen elimination.
What factor enhances amino acid absorption?
Presence of sodium (Na⁺) in the intestinal lumen.
What is the fate of dietary proteins that are not absorbed?
Excreted in feces or converted into bacterial metabolites in the colon.
What is the main carrier protein for amino acids in the blood?
Albumin.
A patient with pancreatic insufficiency presents with protein malabsorption and weight loss. What is the cause?
Lack of pancreatic proteases (trypsin, chymotrypsin, etc.) leading to impaired digestion.
What is the role of gastric acid (HCl) in protein digestion?
Denatures proteins and activates pepsinogen to pepsin.
How does liver disease affect protein metabolism?
Impaired protein synthesis, leading to low albumin and clotting factors.
What are the three main roles of proteins in the body?
Structural (collagen), Functional (enzymes, hormones), and Protective (antibodies).
Which hormones regulate protein metabolism?
Anabolic: Insulin, Growth Hormone; Catabolic: Glucocorticoids, Thyroid Hormones.
What is the role of albumin in blood?
Maintains oncotic pressure and transports hormones, drugs, and fatty acids.
What are two major intracellular proteins responsible for motility?
Actin and Myosin.
What is the main function of immunoglobulins (IgG, IgA, IgM, etc.)?
Provide immunity by recognizing and neutralizing pathogens.
How do heat shock proteins (HSP) function?
Act as molecular chaperones to prevent protein denaturation.
What is the main transcription factor involved in protein synthesis?
RNA polymerase.
A patient with Kwashiorkor presents with edema and hypoalbuminemia. What is the cause?
Severe protein deficiency leading to decreased oncotic pressure.
How does cortisol affect protein metabolism?
Increases protein catabolism to provide amino acids for gluconeogenesis.
What type of proteins are hemoglobin and myoglobin?
Oxygen transport proteins.
What is the main function of the urea cycle?
Elimination of nitrogenous waste (ammonia) by converting it to urea in the liver.
What are the key intermediates in the urea cycle?
Carbamoyl phosphate, Citrulline, Argininosuccinate, Arginine, and Ornithine.
Where does the urea cycle occur?
Liver (cytoplasm and mitochondria of hepatocytes).
What is the rate-limiting enzyme of the urea cycle?
Carbamoyl phosphate synthetase I (CPS1).
A patient with hyperammonemia and neurological symptoms has a urea cycle disorder. What is the treatment?
Low-protein diet, sodium benzoate, and arginine supplementation.
What enzyme removes the amino group from amino acids?
Aminotransferases (Transaminases).
What coenzyme is required for transamination reactions?
Pyridoxal phosphate (Vitamin B6).
What is the fate of carbon skeletons of amino acids?
Used for gluconeogenesis, ketogenesis, or energy production.
Which two amino acids are strictly ketogenic?
Leucine and Lysine.
A newborn has musty odor, intellectual disability, and high phenylalanine. What is the diagnosis?
Phenylketonuria (PKU).
What is the most common method for total protein measurement?
Biuret method.
What test is used for proteinuria detection?
Reagent strips, Heller’s test, or heat coagulation test.
What is the most specific test for detecting monoclonal gammopathies (e.g., multiple myeloma)?
Serum protein electrophoresis (SPE) with immunofixation.
What method is used for amino acid analysis?
High-Performance Liquid Chromatography (HPLC).
A patient with inflammatory syndrome has high fibrinogen and low albumin. What is the diagnostic test?
Serum protein electrophoresis (SPE).
How is CSF protein concentration measured?
Turbidimetric and colorimetric methods.
What is the normal range of serum proteins in adults?
60 – 80 g/L.
A patient with nephrotic syndrome has massive proteinuria (>3.5g/day). What test confirms the diagnosis?
24-hour urine protein analysis.
What is the Guthrie test used for?
Newborn screening for metabolic disorders like PKU.
What test differentiates between exudates and transudates in pleural effusions?
Rivalta test.
