This set of Molecular Endocrinology Multiple Choice Questions & Answers (MCQs) focuses on “Hormones Act through Specific High Affinity Cellular Receptors”.
1. Where do hormones bind to activate the target cells in specific tissues?
a) Receptors
b) Hypothalamus
c) Substrate
d) Axons
View Answer
Explanation: In hormone-sensitive target cells, all hormones function through highly specialized receptors, to which they bind with high affinity. Each type of cell has its own hormone receptor combination, determining the range of its hormone responsiveness.
2. What is the reason for the specificity of hormone action?
a) Structural complementarity between hormones and the glands from which they are produced
b) Structural complementarity between a hormone and its receptors
c) Functional complementarity between hormone and its receptors
d) Functional complementarity between hormones and the glands from which they are produced
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Explanation: Structural complementarity between the hormone and its receptor is the reason for the specificity of hormone action. This interaction is extremely selective. So different effects can be shown by structurally similar hormones. This kind of high affinity of this interaction enable cells to respond to very low hormone concentrations.
3. What is the name of the analysis used to quantify hormone-receptor interaction?
a) Gravimetric analysis
b) Microanalysis
c) Scatchard analysis
d) Combustion analysis
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Explanation: In the production of drugs designed to interfere with hormonal control, the relative specificity and affinity of the drug and the natural hormone must be understood. Scatchard analysis can calculate hormone-receptor associations, resulting in a quantitative calculation of affinity (the dissociation constant for the complex) and the number of hormone-binding sites in a receptor preparation under optimal conditions.
4. What is the possible locus of the hormone and the receptor in the given options below?
a) Axial
b) Intercellular
c) Neuronal
d) Extracellular
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Explanation: Depending on the hormone type, the locus of the encounter between the hormone and the receptor may be extracellular, cytosolic, or nuclear. However, there are certain intracellular consequences of hormone-receptor interaction.
5. What is an example of water-soluble hormones?
a) Insulin
b) Steroids
c) Retinoids
d) Thyroid hormones
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Explanation: Insulin is a peptide hormone which is water soluble. They bind to the cell surface receptors that span the plasma membrane and act extracellularly. All others, including steroid, retinoids and thyroid hormones are all water insoluble hormones and their binding action is different.
6. What happens when the hormone binds to the extracellular domain of the receptor?
a) The hormone undergoes a conformational change
b) The receptor undergoes a conformational change
c) Both the hormone and the receptor undergo a conformational change
d) The target cells undergo a conformational change
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Explanation: The receptor undergoes a conformational change when the hormone binds to its extracellular domain, analogous to the one which is generated by the binding of an effector molecule in an allosteric enzyme. The conformational change activates the hormone’s downstream effects.
7. State whether true or false. “The receptor acts not only as a signal transducer but also as a signal amplifier”.
a) True
b) False
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Explanation: In forming a hormonal receptor complex, a single hormone molecule stimulates a catalyst that generates several second messenger molecules, such that the receptor not only acts as a signal transducer, but also as a signal amplifier. A signaling cascade, a sequence of steps in which a catalyst activates a catalyst, resulting in very large amplifications of the initial signal, will further amplify the original signal.
8. Which hormone regulates the glycogen synthesis and breakdown?
a) Oxytocin
b) Vasopressin
c) Insulin
d) Epinephrine
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Explanation: Glycogen breakdown and synthesis is regulated by epinephrine which acts through a cascade mechanism. It activates another molecule which in turn activates other molecules for the amplification of the initial signals in order to regulate the glycogen metabolism.
9. What is an example of water-insoluble hormone?
a) Thyroid hormones
b) Insulin
c) Epinephrine
d) Adrenaline
View Answer
Explanation: Steroids, retinoids, and thyroid hormones, etc., are water-insoluble hormones. In order to enter their receptor proteins in the nucleus, they readily move across the plasma membrane of their target cells.
10. Who carries the cell signals in water-insoluble hormones?
a) Receptors
b) Hormone-receptor complex
c) Hormones
d) DNA
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Explanation: The hormone-receptor complex itself holds the message for this class of water-insoluble hormones. It interacts with DNA to modify the expression of particular genes, which changes the cell’s enzyme complement which in turn alter the cellular metabolism.
11. Which class of hormones act through plasma membrane receptors?
a) Water-insoluble hormones
b) Fat soluble hormones
c) Water-soluble hormones
d) Steroid hormones
View Answer
Explanation: Water-soluble peptides and amine hormones (for example, insulin and epinephrine) act extracellularly by binding to plasma membrane-spanning cell surface receptors. In general, hormones acting via plasma membrane receptors induce very rapid physiological or biochemical responses.
12. Which class of hormones are known as slow-acting hormones?
a) Water-soluble hormones
b) Peptide hormones
c) Amine hormones
d) Water-insoluble hormones
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Explanation: Water insoluble hormones including thyroid and steroid hormones are known as slow- acting hormones. They induce responses in their target cells only after many hours or sometimes it even takes day to promote the response. Differences in the response time corresponds to different modes of action for the specific hormones.
13. What is the mode of action for fast-acting hormones?
a) Changes the activity of pre-existing enzymes
b) Up regulation
c) Down regulation
d) Alter gene expression
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Explanation: Fast-acting hormones changes the activity of pre-existing enzymes present in the cells. They do this by the mechanism of covalent modification or allosteric regulation. Whereas, slow acting hormones carry out alterations in the gene expression.
14. Which is the correct order of epinephrine cascade mechanism in the regulation of glycogen synthesis and breakdown?
a) Adenylyl cyclase, Cyclic AMP (cAMP), cAMP dependent protein kinase (protein kinase A), Glycogen phosphorylase b, Glycogen phosphorylase b kinase
b) Adenylyl cyclase, Cyclic AMP (cAMP), cAMP dependent protein kinase (protein kinase A), Glycogen phosphorylase b kinase, Glycogen phosphorylase b
c) Glycogen phosphorylase b kinase, Adenylyl cyclase, Cyclic AMP (cAMP), cAMP dependent protein kinase (protein kinase A), Glycogen phosphorylase b
d) Glycogen phosphorylase b kinase, Cyclic AMP (cAMP), cAMP dependent protein kinase (protein kinase A), Glycogen phosphorylase b, Adenylyl cyclase
View Answer
Explanation: Epinephrine stimulates adenylyl cyclase (through its receptor), which produces multiple cAMP molecules for each receptor-bound hormone molecule. In exchange, cyclic AMP activates cAMP-dependent protein kinase (protein kinase A) which activates glycogen phosphorylase b kinase, which in turn activates glycogen phosphorylase b.
15. Give an example of a hormone receptor?
a) cAMP
b) cGMP
c) Tyrosine kinase
d) mRNA
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Explanation: Tyrosine kinases are the receptors with membrane-spanning proteins and broad amino-terminal extracellular domains carrying the site of ligand binding, a juxta membrane domain, a catalytic protein kinase domain, and a COOH-terminus. The receptor tyrosine kinase proteins are encoded by 58 of the 90 distinct tyrosine kinase genes found in the human genome.
Sanfoundry Global Education & Learning Series – Molecular Endocrinology.
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