Tag: mechanism of hormone action

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Questions Related to mechanism of hormone action

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

Which one of the following is not a second messenger in hormone action ?

  1. cGMP

  2. Calcium

  3. Sodium

  4. cAMP
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Second messengers are the organic molecules and sometimes the metal ions, acting as intracellular signals, whose production or release usually amplifies a signal such as a hormone, received at the cell surface. Sodium (Na) is not a second messenger to be discovered. In addition to cyclic AMR Cyclic Guanosine Monophosphate (CGMP) functions as a second messenger in certain cases. Calcium ions (Ca++) also act as second messenger in phospholipase c - ca* second messenger system.

So, the correct answer is 'Sodium'.
Multiple choice zoology endocrine system and chemical co-ordination mechanism of hormone action coordination in human beings- chemical control endocrine system in humans

Choose the correct answer from the alternatives given.
A major difference in the mechanism of action between steroid and peptide hormones is that:

  1. steroid hormones affect the synthesis of proteins, whereas peptide hormones affect the activity of proteins already in the cell

  2. target cells react more rapidly to steroid hormones than they do to peptide hormones

  3. steroid hormones bind to a receptor protein, whereas peptide hormones bind to G protein

  4. steroid proteins affect metabolism, whereas peptide hormones affect membrane permeability
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Peptide hormones are hydrophilic due to which they are unable to cross the lipid plasma membrane. They bind to the receptors on the plasma membrane and affect the activity of proteins inside the cell called secondary messenger. These secondary messengers then perform the action required. The steroid hormones are hydrophobic, they can cross the plasma membrane directly and are able to affect the synthesis of proteins directly in the cells.

Hence, the correct answer is 'steroid hormones affect the synthesis of proteins, whereas peptide hormones affect the activity of proteins already in the cell'.

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

All hypophysiotropic hormones are peptides except.

  1. Corticotropin releasing hormone

  2. Growth hormone inhibitory hormone

  3. Somatostatin

  4. Prolactin release inhibiting hormone
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Prolactin release inhibiting hormone is an amino acid derivative hormone produced in the hypothalamus.

So, the correct answer is 'prolactin release inhibiting hormone'

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

"Secondary messenger" is

  1. Cyclic AMP

  2. ATP

  3. ADP

  4. DNA
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Cyclic adenosine monophosphate is a secondary messenger important in many biological processes. It is a derivative of ATP. When a G-protein–coupled receptor on the surface of a cell binds to its particular ligand, the receptor may stimulate the intracellular production of cAMP by the adenylyl cyclase-associated with that receptor. cAMP can then diffuse through the cytoplasm, where it interacts with various targets. Thus, cAMP serves as a second messenger within a cell.

It is used for intracellular signaling system such as transferring into cells the effects of hormones like glucagon and adrenaline, which cannot pass through the plasma membrane. It is also involved in the activation of protein kinases. Hence option A is correct.

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

Which of the following act as a local messenger?

  1. Carrier protein

  2. Glycoprotein

  3. Phospholipid

  4. Glycolipid
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Messenger proteins (or signaling proteins) carry messages or signals. They provide a means by which cells in one part of the body communicate with cells in another location. In some cases, these proteins can carry a signal from one cellular location to another. The signals can trigger/modulate the immune response, promote cell development/differentiation, alter cell metabolism, or stimulate cell growth. Carrier proteins help specific molecules or ions pass through the plasma membrane. They do not extend through the membrane. They bond and drag the molecules through the bilipid layer and release them on the opposite side. 

Therefore, the correct answer is option A.

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

The signal transduction of steroid hormone across cell is through

  1. Binding of hormone to the cytoplasm receptor and the complex binds to hormone response element on DNA within promoter DNA

  2. Binding of hormone to the transmembrane receptor which initiates the production of the second messenger that activates enzymes which further activates transcription factors

  3. Binding to hormone to the transmembrane receptor which diffuses inside the cell cytoplasm and then activates the enzyme necessary for the activation of transcription factors

  4. Binding of hormone to the cytoplasmic receptor that initiates the production of the second messenger which activates enzymes that further transcription factors
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Steroid hormones, being hydrophobic molecules, diffuse freely into all cells and act within the cell. Steroid hormones secreted by adrenal cortex, ovaries, and testes do not utilize the second messenger to exert their influence. Steroid hormones enter the cytoplasm of a target cell and bind with specific receptor proteins (mobile). Hormone-receptor complex than diffuses into the nucleus and activates specific genes to form a new protein. This protein carries out the specific response for a particular steroid hormone.

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

Arrange the following step in correct sequence found during the mechanism of lipid insoluble hormone (epinephrine) function or action.

A. Second messenger formation
B. Binding to the surface receptor
C. Glycogenolysis
D. Adenylate cyclase activation

  1. C, A, D and B

  2. B, D, A and C

  3. D, B, C and A

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Lipid insoluble hormones such as epinephrine acts or functions on a particular site by binding to it. These hormones have their receptors on the plasma membrane of the target cells. The binding of hormone to the receptor initiates a series of events. These series of events are called as signal transduction. In this, the hormone first binds to the surface receptor. It leads to the activation of the enzyme adenylate cyclase. This enzyme converts the ATP into cyclic AMP or cAMP inside the cell. This cAMP acts as second messenger. This cAMP then activates cAMP-dependent protein kinase called protein kinase A. This proteni kinase A triggers a series of molecular interactions that leads to glycogenolysis. This results in the synthesize of glucose from glycogen.

Thus, the correct answer is 'B, D, A and C.'

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

Steroid hormones 

  1. Receptors are predominantly present in the cytosol

  2. Are lipophobic

  3. Act through altering the activity of proteins in the target cell

  4. Bind to the lipophilic receptors on cell surface
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Steroid hormone receptors are found on the plasma membrane, in the cytosol and also in the nucleus of target cells. They are generally intracellular receptors (cytoplasmic) and initiate signal transduction for steroid hormones, which lead to changes in gene expression over a time period of hours to days. 

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

According to the accepted concept of hormone action, if receptor molecules are removed from target organs

  1. The target organ will continue to respond to the hormone without any difference.

  2. The target organ will continue to respond to the hormone but will require higher concentration.

  3. The target organs will not respond to the hormone.

  4. The target organ will continue to respond to the hormone but in the opposite way.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Though hormones are released into the blood stream and hence can reach all cells, yet they affect only those cells which have hormone specific receptors. Thus, binding of hormone to receptor is crucial irrespective of presence of receptors inside the cell or on its surface. This makes options A and D incorrect as absence of receptors renders the cell unaffected by hormonal action. Option B is incorrect as hormone-receptor binding is essential step in hormonal action. Thus, in absence of receptors, the target organ will no longer respond to hormone. Option C is correct.