Tag: mechanism of hormone action

Questions Related to mechanism of hormone action

Steroid hormones easily pass through plasma membrane by simple diffusion because they

zoology endocrine system and chemical co-ordination mechanism of hormone action coordination in human beings- chemical control endocrine system in humans

  1. Are lipid soluble

  2. Are water soluble

  3. Enter through pores

  4. Contain carbon and hydrogen

Show answer
Correct Option: A
Explanation:

Steroid hormones are made up of fats and they are not soluble in water. They are hydro phobic in nature. Hence they can easily pass through the plasma membrane by simple diffusion. 

So, the answer is 'Are lipid soluble'. 

Which one of the following pairs of hormones are the examples of those that can easily pass through the cell membrane of the target cell and bind to a receptor inside it(mostly in nucleus)?

zoology endocrine system and chemical co-ordination mechanism of hormone action coordination in human beings- chemical control endocrine system in humans

  1. Insulin, glucagon

  2. Thyroxine, insulin

  3. Somatostatin, oxytocin

  4. Cortisol, testosterone

Show answer
Correct Option: D
Explanation:

Cortisol and testosterone are lipid soluble hormones, which can directly pass through the cell membrane of the target cell and bind with intracellular receptors. So, the correct answer is option D.

Which of these is not a secondary messenger?

zoology endocrine system and chemical co-ordination mechanism of hormone action coordination in human beings- chemical control endocrine system in humans

  1. cAMP

  2. cGMP

  3. Calcium

  4. Sodium/Mg

Show answer
Correct Option: D
Explanation:

Secondary messengers are intracellular signalling molecules released by the cell in response to exposure of extracellular signalling molecules-the first messengers. Second messengers trigger physiological changes such as proliferation, migration, survival, etc. Some common secondary messengers are cAMP(Cyclic Adenosine Mono Phosphate), cGMP(Cyclic Guanosine Mono Phosphate), Calcium ion, IP$ _3$, etc. So all the given options serve as secondary messengers except the Sodium/Mg ions.

So, the correct answer is 'Sodium/Mg'.

Steroid hormones 

zoology endocrine system and chemical co-ordination mechanism of hormone action coordination in human beings- chemical control endocrine system in humans

  1. Work via second messenger

  2. Trigger rapid, short term response in cells

  3. Alter the activity of genes

  4. Initiate open channels in plasma membrane

Show answer
Correct Option: C
Explanation:
Steroid hormones are derived from cholesterol. They are in the form of lipids. Their receptors are intracellular i.e. located inside the cell. These hormones are lipid soluble and hence, cross the cell membrane easily to enter the cell. The hormone binds to receptor and a hormone-receptor complex is formed. The complex then binds to transcription factors which then bind to DNA and this causes activation and transcription of a particular gene. This leads to synthesis of specific proteins that affect the metabolism of cells.
Hence, steroid hormones alter the activity of genes.
So, the correct answer is 'Alter the activity of genes'.

Signalling between cells usually results in activation of protein by

zoology endocrine system and chemical co-ordination mechanism of hormone action coordination in human beings- chemical control endocrine system in humans

  1. Kinases

  2. Proteases

  3. Lipases

  4. Nucleases

Show answer
Correct Option: A
Explanation:
Signalling is the communication between cells by means of signalling molecules. When a ligand binds to its receptor, ligand-receptor complex is formed which activate protein kinases. Kinases are the enzymes that transfer phosphate group to the target cells. Phosphorylation of target cells cause different changes in the cell.
So, the correct answer is 'Kinases'.

Which of these can pass easily through cell membrane of target cells and bind to internal receptors?

zoology endocrine system and chemical co-ordination mechanism of hormone action coordination in human beings- chemical control endocrine system in humans

  1. Thyroxine, insulin

  2. Somatostatin, Oxytocin

  3. Insulin, glucagon

  4. Cortisol, testosterone

Show answer
Correct Option: D
Explanation:

A. Thyroxine, insulin hormones are protein hormones. 

B. Somatostatin, oxytocin are protein hormones. 
C. Insulin, glucagon are protein hormones.
D. Cortisol, testosterone are steroid hormones. 
Steroid hormones are made up of fats and are not soluble in water, hence they can easily pass through the cell membrane.
So, the answer is Cortisol, testosterone. 

(A) Every receptor is unique for a hormone
(B) Every hormone is unique for a receptor.

zoology endocrine system and chemical co-ordination mechanism of hormone action coordination in human beings- chemical control endocrine system in humans

  1. Both true

  2. Both false

  3. A true B false

  4. B true B false

Show answer
Correct Option: A
Explanation:

In the human body, every receptor is specific for a hormone and every hormone is specific for a receptor.

So, the correct option is ‘Both true’.

Which one of the following is proteinaceous in chemical nature?

zoology endocrine system and chemical co-ordination mechanism of hormone action coordination in human beings- chemical control endocrine system in humans

  1. Thyroxine

  2. Insulin

  3. Progesterone

  4. Oxytocin

Show answer
Correct Option: A
Explanation:

Thyroxine is a proteinaceous hormone, formed by the addition of iodine to amino acid tyrosine which is then combined with protein thyroglobulin

So, the correct answer is 'Thyroxine'

A dehydration synthesis reaction is also known as

zoology endocrine system and chemical co-ordination mechanism of hormone action coordination in human beings- chemical control endocrine system in humans

  1. A condensation reaction

  2. A hydrolysis reaction

  3. An isomeric reaction

  4. An energy-releasing reaction

Show answer
Correct Option: A
Explanation:

Dehydration means removal of water. It is a synthesis reaction where polymerization occurs in which the monomers are bound together which releases water as the end product or byproduct.

Hence, the correct answer is 'A condensation reaction'.

Choose the correct answer from the alternatives given.
Pick out the false statement pertaining to acromegaly:

zoology endocrine system and chemical co-ordination mechanism of hormone action coordination in human beings- chemical control endocrine system in humans

  1. oversecretion of somatotropin after adolescence causes this disease

  2. the person gets a giant stature

  3. long bones of the limbs elongate

  4. the person looks like a gorilla

Show answer
Correct Option: B
Explanation:

GH or STH (Growth or Somatotropin Hormone) stimulates body growth, protein, fat and carbohydrate metabolism. Hypersecretion of this hormone during the period of skeleteal growth causes gigantism characterized by excessive growth of bones, with the enlargement of internal organs as well. Hypersecretion in adulthood causes acromegaly. Here thr, bones become abnormally thick due to ossification of periosteum and thickening of soft tissues as well. 

So the correct answer is the person gets a giant structure.