Select all the true statements about second messenger systems. Amine hormones an
ID: 50259 • Letter: S
Question
Select all the true statements about second messenger systems. Amine hormones and polypeptide hormones rely on second messengers. Second messenger systems amplify the signal generated by a hormone. Adenylate cyclase (adenylyl cyclase) converts CAMP to ATP. Protein kinase A, which phosphorylates enzymes in the cell, is activated by CAMP. Membrane receptors activate enzymes that catalyze the synthesis of second messengers. Estradiol receptors are located on the cell surface. Inositol triphosphate (IP3) and calcium ions (Ca2+) are examples of second messengers.Explanation / Answer
1. Amine hromones and polypeptide hormones rely on second messengers. Since these two types of hormones are hydrophilic, they cannot cross the membrane. The steroid hormones, on the other hand, are hydrophobic/lipophilic, and can easily cross the membrane. Due to this reason, peptide and amine hormones rely on a second messenger.
2. Each second messenger is coupled to multiple effector molecules. As a result, a cascase of events occur upon activation of a second messenger, thus amplifying the original signal. for example cAMP directly activates cAMP dependent protein kinase , amplify the signal produced.
3. protein kinase A which phosphorylates the enzymes in the cell is activated by cAMP , cAMP directly activates the protein kinase A .
4. Membrane receptors activate the enzymes that catalyze the synthesis of second messengers ---- binding of the two leads to increase or decrease in the concentration of intracellular signalling molecules termed secondary messengers.
5. Estradiol receptors occur both on the cell surface and on the nuclear membrane surface. Those that occur on the surface of plasma membrane are termed nuclear estrogen receptors, whereas those that are present on the plasma membrane are termed mERs. They are G protein coupled receptors.
6. The action of phospholipase C on Phosphoinositol phosphate produces IP3 and DAG. IP3 and calcium ions are second messengers --- IP3 is a small polar molecule that is released into the cytosol where it acts to signal the release of calcium ion from ER . as the level of calcium will increase , it will effect the variety of target proteins
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