1. What is a phosphorylation cascade? What chemical changes have to occur in ord
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Question
1. What is a phosphorylation cascade? What chemical changes have to occur in order to transmit this type of signal? What dictates how long a signal transduction pathway involving a phosphorylation cascade will remain on? What type of enzyme activity turns phosphorylation cascades off?
2. What is a second messenger? What are the major examples of second messengers we covered in class, and what basic principles do they have in common? How do cell effector molecules respond to second messenger signaling? How is second messenger production/release controlled? How is second messenger signaling turned off?
3.What is the difference between a calcium pump and a ligand-gated calcium channel?
Explanation / Answer
Phosphorylation cascade is the process in which series of steps involved for addition of phophoryl group. This change in the cell induces the activity of enzyme. That may activate or deactivate the enzyme function. Kinase enzyme plays very important role in the activity of signal production for interaction in between various pathways. ATP acts as source of phosphate which provides the phosphate group for phosphorylation. In case of switch off the signal the dephophorylation occurs. In dephophorylation the hydrolase enzyme breaks the ester bond. After that the phophotase cause the dephosphorylation which results in switch off signal from pathway. MAP kinase cascade is the well known example of phosphorylation. In that the Ras molecule activates the Raf kinase enzyme that further activates the MEK kinase. The end result is the activation of ERK kinase.
Second Messengers are the signaling molecule released by cells to induce the physiological changes for example differentiation, proliferation, survival, migration and apoptosis. These molecules react after the release of first messenger molecules. Secondary molecules are cyclic AMP, diacylglycerol and inositol triphosphate. There mainly three types of secondary messenger molecules which are hydrophobic molecules, hydrophobic molecules, Gases.
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