General Biochemical Flashcards
The primary component of pulmonary surfactant
Dipalmitoyl Phosphatidylcholine
Inhibitor X and inhibitor Y bind an enzyme. Inhibitor X reversibly binds the same site as the substrate, whereas inhibitor Y interacts with the enzyme at a different location. How is the maximum velocity of the reaction between the enzyme and substrate affected when inhibitors X and Y bind the enzyme separately?
The binding of a competitive inhibitor lowers the affinity of the enzyme for the substrate (increased Michaelis-Menten constant, or Km), but the maximum velocity (Vmax) of the reaction remains unchanged. Increasing the concentration of substrate can overcome the effects of a competitive inhibitors. Binding of a noncompetitive inhibitor does not change the affinity of the enzyme for the substrate, but it does decrease the maximum velocity.
I-cell disease (inclusion cell disease/mucolipidosis type II)?
Inherited lysosomal storage disorder; defect in N-acetylglucosaminyl-1-phosphatransferase➡️failure of the Golgi to phosphorylate mannose residues (i.e., ⬇️mannose-6-phosphate) on glycoproteins➡️proteins are secreted extracellularly rather than delivered to lysosomes. Results in coarse facial features, clouded corneas, restricted joint movement, and high plasma levels of lysosomal enzymes. Often fatal in childhood.
Methemoglobinema
In which the oxygen-carrying iron is present in the oxidized (ferric Fe3+) state instead of the reduced (ferrous, Fe2+) state. Methemoglobin cannot bind to oxygen. Moreover, any remaining ferrous hemes in the hemoglobin tetramer exhibit increased oxygen affinity (i.e., the oxygen dissociation curve is shifted to the left). Thus, sings and symptoms of methemoglobin reflect decreased blood oxygen content and and an even greater decrease in oxygen delivery to tissues (i.e., cellular hypoxia). Symptoms include headache, dizziness, nausea, shortness of breath, Confusion, Seizures, and coma. Because oxygen diffusion at the alveolar level is not impaired, the arterial partial pressure of oxygen will be normal. Blood may have a characteristic muddy color secondary to the oxidization state of iron. Methemoglobin may occur as an adverse effect of oxidizing agents such as sulfonamides, dapsone, and local anesthetics (e.g., benzocaine), from hereditary hemoglobin abnormalities, or secondary deficiency of the reduced form of nicotinamide adenine dinucleotide. Methylene blue has been shown to increase the conversion of Fe3+ back to Fe2+. An alternative treatment for methemoglobin is ascorbic acid (vit C).
Under normal circumstances, which substance is produced in the innermost cells of the layer “i.e., the layer closest to the blood) where these plaques develop?
Plaque/atheroma of extracellular lipid develop within the intima of the arterial wall. The intima lines the luminal side of the artery; it is the most “intimate” with the blood. The innermost layer of cells of the intima is therefore the endothelial cells. In a nonpathologic state, endothelial cells prevent plaque formation by releasing antithrombotic factors such as prostacyclin and nitric oxide.
Alkaptonuria
AR associated defect is on chromosome 3. A congenital deficiency of homogentisic acid oxidase, an enzyme in the pathway that degrades tyrosine. Deficiency of this enzyme causes accumulation of homogentisic acid, which leads to cartilage (joint) damage, heart valve damage, and formation of kidney stones. Notably, homogentisic acid is excreted in the urine, making the urine turn black upon standing.
