Homework multiple choice questions 1. In which of the following sites are calciu

Question

Homework multiple choice questions

1. In which of the following sites are calcium ions often stored in a variety of cells?

   a. the nucleus

   b. the peroxisomes

   c. the nucleolus

   d. the SER

   e. a and c

2. How does IP3 get from the plasma membrane where it is made to the receptor on the SER?

   a. It is carried there by a transport molecule

   b. It diffuses

   c. It crawls

   d. It osmoses

   e. It is moved enzymatically

3. Which enzyme below terminates the response to cAMP throught the destruction of cAMP molecules present in the cell?
   a. phosphorylase kinase

   b. phosphorylase

   c. glycogen synthase

   d. phosphodiesterase

   e. a, d, and c

4. __________ is a small protein linked covalently to other proteins, thereby marking those proteins for degradation by proteasomes.

   a. Chaperonin

   b. Ubiquitin

   c. Proinsulin

   d. Transcription

   e. Tubulin

Explanation / Answer

In which of the following sites are calcium ions often stored in a variety of cells

Ans,d. the SER

Smooth Endoplasmic Reticulum is the major site of Ca++ storage. in the cell the major site of storage of Calcium is mitochondria and Endoplasmic reticulum. these are released by the action of IP3. IP3 is Secondary messengers which is activated by the activation of the G-Protein Coupled Receptors. upon activation IP3 diffuses through the cytoplasm and binds to the Receptors on ligand-gated Ca++ channel which is found on the surface of the Endoplasmic reticulum activates Ca++ release from intracellular stores.

2. How does IP3 get from the plasma membrane where it is made to the receptor on the SER

Ans. b. It diffuses

when ligand binds to G-protein coupled receptor it activates the isozyme which cleaves PIP2 to IP3 and DAG, these both are secondary messenger which activates other enzymes and proteins involved in signaling system. IP3 is soluble molecule which diffuse through the cytoplasm reaches the cell and binds to specific receptors on the Endoplasmic Reticulum activates ligand-gated Ca++ channel.

3.Which enzyme below terminates the response to cAMP throught the destruction of cAMP molecules present in the cell

Ans.d. phosphodiesterase

cAMP is secondary messenger which is produced from ATP by the action of adenylate cyclase. activated cAMP activates protein kinases and regulates ion channels.Phosphodiesterase are the enzymes which invovles in degradation of Phosphodiester bond in cAMP and converts cAMP into AMP. by conversion these enzymes involves in regulation of siganling pathway.

4.__________ is a small protein linked covalently to other proteins, thereby marking those proteins for degradation by proteasomes

Ans.b. Ubiquitin

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