This set of Molecular Endocrinology Multiple Choice Questions & Answers (MCQs) focuses on “Obesity and Regulation of Body Mass”.
1. What is the BMI index for normal, overweight and obese people?
a) Normal: < 25, Overweight: 25 – 30, Obese: > 30
b) Normal: < 19, Overweight: 19 – 25, Obese: > 27
c) Normal: > 25, Overweight: 30 – 35, Obese: > 40
d) Normal: > 30, Overweight: 35 – 40, Obese: > 50
View Answer
Explanation: In the U.S. population, 30 percent of adults are obese and another 35 percent are overweight, measured as (weight in kg) / (height in m)2, as described in terms of body mass index (BMI). A BMI below 25 is considered normal; a person with a BMI between 25 and 30 is overweight; obesity is marked by a BMI greater than 30.
2. What is the name of the hormone produced by adipose tissue?
a) Adipolipase
b) Adipokines
c) Kinases
d) Adipokinin
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Explanation: A feedback signal originating in adipose tissue influences the brain centers that control eating behavior and activity. The first such factor, leptin, was discovered in 1994, and subsequent research revealed that adipose tissue is an important endocrine organ that produces peptide hormones, known as adipokines.
3. Among the options given below, which is an example of adipokine hormone?
a) Inulin
b) Kinetin
c) Leptin
d) Melatonin
View Answer
Explanation: Leptin is an adipokine (167 amino acids) which acts on the brain. It acts on the hypothalamus to curtail hunger. Leptin was first detected in laboratory mice as the product of a gene called OB (obese).
4. How is the two defective copies of the obese (OB) gene represented?
a) OB/OB
b) Ob/Ob
c) oB/oB
d) ob/ob
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Explanation: The ob/ob genotype represents two abnormal versions of the obese gene. A mutated version of the gene is signified by lower case characters. Elevated plasma cortisol levels are seen in animals who exhibit this gene.
5. Which hormone receptor is encoded by diabetes gene (DB)?
a) Leptin receptor
b) Oxytocin receptor
c) Peptide receptor
d) Kinetin receptor
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Explanation: It has been discovered that the DB (diabetic) gene also has a role in the regulation of appetite. Obese and diabetic animals are animals with two deficient versions of the diabetes gene (db/db). The leptin receptor is encoded by the DB gene. The signaling feature of leptin is lost when the receptor is dysfunctional.
6. What message is carried by the hormone leptin regarding the fat metabolism in brain?
a) Fat reserves are insufficient
b) Fat reserves are sufficient
c) Cells lack fuel
d) Fat should be broken down
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Explanation: Leptin bears the message that fat supplies are adequate and supports a decrease in fuel consumption and a rise in energy expenditure. Interaction of the leptin receptor in the hypothalamus shifts the release of synaptic impulses related to appetite to the area of the brain.
7. Which hormone is produced and released by the orexigenic neuron to stimulate appetite?
a) Alpha melanocyte stimulating hormone (alpha – MSH)
b) Neuropeptide C (NPC)
c) Neuropeptide Y (NPY)
d) Beta melanocyte stimulating hormone (beta – MSH)
View Answer
Explanation: By generating and releasing neuropeptide Y (NPY), the orexigenic (appetite – stimulating) neurons induce feeding, allowing the next neuron in the circuit to transmit the signal to the brain to eat. In persons who eat ravenously, the high concentration of NPY is the reason for obesity.
8. Which hormone is produced and released by anorexigenic neuron to suppress the appetite?
a) Beta melanocyte stimulating hormone (beta – MSH)
b) Neuropeptide C (NPC)
c) Cortisol
d) Alpha melanocyte stimulating hormone (alpha – MSH)
View Answer
Explanation: The anorexigenic (appetite – suppressing) neurons in the arcuate nucleus develop alpha melanocyte–stimulating hormone (alpha – MSH; also known as melanocortin), produced from its polypeptide precursor pro opiomelanocortin. Alpha – MSH release, allows the next neuron in the circuit to send the warning signal to stop eating.
9. What factor(s) decides the amount of the hormone leptin released by the adipose tissue?
a) Number and size of white and brown adipocytes
b) Number of white adipocytes
c) Number of brown adipocytes
d) Size of brown adipocytes
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Explanation: The amount of leptin that adipose tissue produces depends on both the number of adipocytes and their size. Leptin levels in the blood decrease, NPY production drop, and the mechanisms in adipose tissue are revered when weight loss reduces the mass of lipid tissue.
10. What is the name of the mechanism of leptin transduction in the hypothalamus?
a) cAMP cascade
b) JAK – STAT mechanism
c) Fat – STAT mechanism
d) Lac – STAT mechanism
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Explanation: The leptin signal is transduced by the JAK – STAT system, a process often used by receptors for interferon and growth factors. When leptin binds to the extracellular domains of two monomers, the leptin receptor, which has a single transmembrane portion, dimerizes. Both monomers are phosphorylated by a Janus kinase (JAK) on the Tyr residue of their intracellular domain.
11. Which enzyme phosphorylates the monomers in which leptin is bound during fat metabolism?
a) Protein kinase A
b) Lipases
c) Janus Kinase (JAK)
d) Phosphatase
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Explanation: Janus Kinase (JAK) enzyme helps in the phosphorylation of the monomers in which leptin is bound. JAK enzyme phosphorylates these monomers on a tyrosine residue at their intracellular domains.
12. Which among the following are the three proteins which are collectively known as fat – STATS?
a) STATs 1,2, and 3
b) STATs 3, 4, and 5
c) STATs 3,5 and 1
d) STATs 3,5 and 6
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Explanation: STATs 3, 5, and 6 are collectively known as fat – STATS. They take part in the Janus Kinase – Signal Transducers and Activators of Transcription (JAK – STAT) mechanism. They act as transcription activators as well as signal carriers in this mechanism.
13. What is the reason for the triggering of increased catabolism and thermogenesis by leptin hormones, in the brown and white adipose tissues?
a) Due to the increased synthesis of mitochondria
b) Due to the increased synthesis of liposomes
c) Due to the decreased synthesis of mitochondria
d) Due to the decreased synthesis of liposomes
View Answer
Explanation: The higher level of thermogenesis and increased catabolism in brown and white adipose tissues is due to the increased synthesis of mitochondria. Leptin is the hormone that triggers this activity.
14. Which hormone acts through the beta – 3 adrenergic receptors to stimulate the transcription of UCP1 gene in the adipose tissues?
a) Epinephrine
b) Norepinephrine
c) Insulin
d) Leptin
View Answer
Explanation: In the adipose tissues, the increased synthesis of the hormone norepinephrine occurs. It acts through the beta – 3 adrenergic receptors in order to induce the transcription of UCP1 gene. As a result, the electron transfer and oxidative phosphorylation uncouples in this tissue which leads to thermogenesis as it consumes fat.
15. Decreased leptin signal in the hypothalamus reduces the production of thyroid hormones and sex hormones.
a) True
b) False
View Answer
Explanation: In the hypothalamus, when the leptin signals are low, the synthesis of thyroid hormones and sex hormones are reduced. This in turn leads to the decreased basal metabolism and prevents reproductive abilities in an individual.
Sanfoundry Global Education & Learning Series – Molecular Endocrinology.
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