This set of Molecular Endocrinology Multiple Choice Questions & Answers (MCQs) focuses on “Mechanisms of Disease and Receptor Serine Kinases”.
1. What is the role of mutations in hormone receptor function?
a) Decreases number of receptors
b) Increases number of receptors
c) Block receptor function
d) Induces receptor function
View Answer
Explanation: Mutations can lead to a decrease in receptor numbers. Mutations that reduce the number of receptors by at least three pathways have been described in the case of the insulin receptor. Insulin receptor gene mutations can make the cell immune to insulin’s biological action.
2. Mutations in the gene encoding which tyrosine kinases causes multiple endocrine neoplasia?
a) MET tyrosine kinase
b) RET tyrosine kinase
c) RAC tyrosine kinase
d) CBL tyrosine kinase
View Answer
Explanation: Types 2A and 2B multiple endocrine neoplasia syndromes and hereditary. Thyroid medullary carcinoma is caused by defects in the RET tyrosine kinase encoding gene. For members of the glial cell line-derived neurotrophic factor (GDNF) family of extracellular signalling molecules, the RET proto-oncogene encodes a tyrosine kinase receptor.
3. Which amino acid residues in the RET tyrosine kinase participate in the formation of intramolecular disulfide bonds?
a) Serine
b) Lysine
c) Cysteine
d) Valine
View Answer
Explanation: Cysteine residues usually engage in the formation of intramolecular disulfide bonds in the extracellular domain of RET. The mutation of one of the cysteine residues leaves an unpaired residue of cysteine that encourages RET molecules to be dimerized.
4. The receptor’s intrinsic functions may be disrupted by mutations.
a) True
b) False
View Answer
Explanation: Mutations can affect the receptor’s intrinsic activities. Mutations that decrease the affinity of insulin binding or that inhibit the function of receptor tyrosine kinase have been documented in the case of the insulin receptor.
5. Serine kinase receptor has several features in common with tyrosine kinase receptor.
a) True
b) False
View Answer
Explanation: There are several features that receptor serine kinases have in common with receptor tyrosine kinases. Both receptor classes, for example, have ligand-binding N-terminal extracellular domains.
6. Inhibitory antireceptor autoantibodies were first identified in patients with which disease?
a) Syphilis
b) Myasthenia gravis
c) Phenylketonuria
d) Maple Syrup Urine disease
View Answer
Explanation: In patients with myasthenia gravis, inhibitory antireceptor autoantibodies were first identified. Antibodies to the nicotinic acetylcholine receptor disrupt neuromuscular transmission in this neurologic condition, by accelerating receptor degradation.
7. In which type of insulin resistance does the autoantibody blocks the insulin action?
a) Type B
b) Type A
c) Type C
d) Type 1
View Answer
Explanation: Insulin receptor autoantibodies were later found to inhibit insulin activity in severe insulin resistance type B syndrome. At least two pathways induce insulin resistance where anti-receptor antibodies block receptor-binding insulin, and antibodies accelerate degradation of the receptor.
8. Which disease is the first example of stimulatory antireceptor autoantibodies?
a) Syphilis
b) Phenylketonuria
c) Myasthenia gravis
d) Graves’ disease
View Answer
Explanation: The first example of stimulatory antireceptor autoantibodies was Graves’s disease. In Graves’ disease, autoantibodies are directed towards the thyroid-stimulating hormone (TSH) receptor.
9. Which among the following is an example of a case where a non-related ligand activates the receptor other than the physiological ligand?
a) Activation of TSH by antireceptor antibodies
b) Activation of TSH by Vitamin D
c) Activation of TSH by Vitamin A
d) Activation of TSH by cAMP
View Answer
Explanation: Antireceptor antibodies can activate the TSH receptor and stimulate thyroid gland growth and thyroid hormone hypersecretion. This natural experiment shows that ligands other than the physiologic ligand can activate the receptor.
10. Where do the serine kinase receptors phosphorylate their substrate?
a) Tyrosine residues
b) Serine and threonine residues
c) Lysine residues
d) Arginine residues
View Answer
Explanation: Receptor tyrosine kinases phosphorylate tyrosine residues. While receptor serine kinases phosphorylate serine and threonine residues in their protein substrates. Tyrosine kinases are enzymes that phosphorylate tyrosine residues in various substrates selectively.
11. The biological actions of which family of ligands are mediated by receptor serine kinases?
a) Transforming growth factor-β (TGF-β)
b) Insulin growth factor
c) CBL family
d) FASH domain
View Answer
Explanation: Receptor serine kinases mediate the biological activities of the transforming growth factor-β (TGF-β) complex, a single, large family of ligands. The occurrence of six conserved cysteine residues is defined by this.
12. Which are the two classes of TGF-β family encoded by the 42 genes of the human genome?
a) Activin and MIS
b) Activin and Insulin
c) MIS and CBL
d) Activin and CBL
View Answer
Explanation: In the TGF-β family, the human genome includes 42 genes encoding cytokines that are classified into two groups. Both are the family of activin/TGF-β and the family of müllerian inhibitory content (MIS)/bone morphogenic protein (BMP).
13. What leads to the activation of the type 1 receptor (RI) by the type 2 receptor (RII) of the TGF-β family?
a) Physical interaction between RI and RII
b) Transport of RI and RII
c) Dephosphorylation of RII
d) Dephosphorylation of RI and RII
View Answer
Explanation: A physical interaction between the type I receptor (RI) and the type II receptor (RII) is facilitated by ligand binding to the receptor serine kinases. As a result, by phosphorylating one or more serine residues in the GS domain, the RII receptor stimulates the RI receptor.
14. How does the ligand trigger receptor activation in the case of the MIS/BMP family of cytokines?
a) Simultaneous binding to RI and RII
b) Binding to RI with low affinity
c) Binding to RII with low affinity
d) Binding to RI and RII with low affinity
View Answer
Explanation: The ligand binds to the isolated RI receptor with high affinity and to the RII receptor with comparatively low affinity in the case of the MIS/BMP cytokine family. The ligand will bind to RI and RII at the same time, offering a reason for its potential to facilitate a physical RI-RII relationship.
15. How does the ligand trigger receptor activation in the case of the activin/TGF-β family of cytokines?
a) Binds to RII with high affinity
b) Binds to RI with high affinity
c) Binds to RI and RII with high affinity
d) Binds to RI and RII with low affinity
View Answer
Explanation: TGF-β binds with high affinity to RII but does not interact specifically with RI in the case of the activin/TGF-β family of cytokines. TGF-β binding, however, tends to cause a confirmative transition in RII, encouraging a direct binding relationship between RII and RI intracellular domains.
Sanfoundry Global Education & Learning Series – Molecular Endocrinology.
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