Hormone Synthesis Quiz Flashcards
A 53-year-old Type II diabetic is seen by her regular physician for a checkup. The patient has been on insulin for 14 years but still has some beta cell secretory function. Since the patient takes insulin injections, what can the physician use as a marker for endogenously secreted insulin?
A. Albumin level
B. C-peptide level
C. Total insulin
D. Insulin level subtracting amount injected
E. Glucagon levels
B. C-peptide level
C-peptide is the central domain of pre-pro-insulin. It is cleaved out of the hormone but stays associated with mature insulin. C-peptide is secreted in a 1:1 ratio with insulin but has a much longer half-life in plasma. Thus, the injected insulin is indistinguishable from endogenous but the concentration of C-peptide indicates how much endogenous insulin was made.
A neonatal heal prick blood sample is analyzed for a newborn whose parents are 2nd cousins from Saudi Arabia. The analysis shows elevated levels of phenylalanine. Another analysis indicates normal phenylalanine hydroxylase activity. If the child has a deficiency in Tetrahydrobiopterin (BH4), what other hormone level change should be seen (if any)? A. Decreased ACTH B. No other hormone changes C. Decreased serotonin D. Increased Vasopressin E. Increased L-Dopa
C. Decreased serotonin
BH4 is required for the synthesis of tyrosine, catecholamines, serotonin and melanin. If the BH4 levels are low or not regenerated, the levels of tyrosine, catecholamines, serotonin and melanin decreases and the level of phenylalanine (the precursor for tyrosine) increases. The majority of elevated phenylalanine in persons form Saudi Arabia is due to a defect in recycling BH4.
A 3.5-year-old-boy with a history of hypertonia, chorea, muscular hypoplasia, unable to talk and unable to walk without assistance is referred for genetic analysis. Additionally, the child has an apparently normal thyroid and normal T3/T4 levels. DNA sequencing reveals that the child has a 3 amino acid deletion in the SLC16A2 gene which is a transporter responsible for the transport of T3 into the developing brain in utero. This deletion is known to cause improper folding of the protein and a loss of its expression in the neuronal cell surface. How does the loss of a transporter result in low extracellular T3 in the developing brain?
A. Thyroxine binding globulin, transthyretin and albumin bind the T3 irreversible in utero.
B. Without a high affinity transporter, the T3 has a shorter half-life in blood.
C. The loss of the transporter up regulated the production of T3/T4 but there isn’t enough blood carrier proteins to handle the excess T3/T4.
D. The transporter is needed to load T3/T4 onto the blood carriers, Thyroxine binding globulin, transthyretin, and albumin.
E. Without a high affinity transporter, the T3 stays attached to Thyroxine binding globulin, transthyretin, and albumin in the blood.
E. Without a high affinity transporter, the T3 stays attached to Thyroxine binding globulin, transthyretin, and albumin in the blood.
Carriers proteins must have a relatively high affinity for the hormone to keep it bound during circulation in plasma. However, a receptor or transporter with a high affinity is needed to get the hormone onto or into the cell target. Cells without receptors or transporters will not receive the hormone. Carrier proteins therefore increase the half-life of hormones by protecting them from degradation or reacting to the wrong cells. Irreversible binding to the carriers would mean that the hormone would not dissociate in the tissues where it is needed.
Neurophysin I and II are produced on genes 15 kb apart. Additionally they are both produced as a part of a pre-pro-hormone where the hormone is just 9 amino acids long. Which of the following is a difference between Neurophysin I and II?
A. One has 2/3 the molecular weight of the other.
B. Phosphorylation
C. One is n-terminal to its hormone the other is c-terminal to its hormone
D. Glycosylation
E. One dimerizes, one remains a monomer
E. One dimerizes, one remains a monomer
Neurophysin II dimerizes where as Neurophysin I does not. Otherwise, the two proteins are matured and modified in the same manner. Neither is phosphorylated nor glycosylated. They have similar molecular weights.
Angiotensinogen is matured in the blood instead of intracellularly. Which organ is required for maturation of Angiotensinogen to Angiotensin II? A. Heart B. Liver C. Spleen D. Small Intestines E. Lung
E. Lung
Angiotensinogen is secreted from the liver then travels via plasma to the kidneys where the enzyme Renin converts it to Angiotensin I. From the kidney the hormone continues to the lung where it is further digested by Angiotensin converting enzyme (ACE). It then act on the smooth muscle of the vasculature to directly regulate blood pressure and indirectly regulate blood volume by increasing the synthesis of vasopressin (ADH).
