Cell receptor and communication

Question 1

Cell to cell signaling mechanism

Answer 1

1, Contact dependent signaling : molecule bound with the membrane interact with the membrane bound receptor Eg: important during development, cancer and in immune response
2. Paracrine: molecule released locally act on the cells nearby
3. Autocrine: molecule released by the cell act on the same cell or cells of the same type
4. Endocrine: molecule is released into the blood stream and act on the target cell further away (throughout the body)

Question 2

Gap junction

Answer 2

forms between adjacent cells and which allows the signaling molecule to pass from one cell to other if they are <1200 Da.
Permeability of gap junction is regulated by cytosolic on Ca, H, membrane potential, cAMP

Question 3

Ligand gated ion channels

Answer 3

regulate synaptic signaling between electrically excited cells

Question 4

GPCR

Answer 4

regulate activity of enzymes and other proteins. Contains alfa, beta and gamma subunits

Question 5

Enzyme linked Receptor

Answer 5

act as an enzyme or regulate activity of other enzymes. They are kinases or protein associated kinases causes phosphorylation of protein.

Question 6

Nuclear receptor

Answer 6

Signalling molecules those are hydrophobic pass through the cell membrane and attaches to the receptor in cytoplasm which then translocated into the nucleus. For some proteins receptors is present in the nucleus such as thyroid - after activation leads to transcription of genes.

Question 7

Regulated intramembrane proteolysis (RIP)

Answer 7

some proteins are not a receptor and they subserve and produce receptor like effect. when ligand binds to receptor such protein undergoes regulated intramemebrane proteolysis and releases intracellular peptide which then activates secondary messenger to enter nucleus and perform gene expression. Eg: sterol regulatory element binding protein in synthesis of cholesterol

Question 8

Reversible molecular switches

Answer 8

In intracellular signaling pathway some proteins they pass the message straight to another protein and act as a switch which turned on due to hormone receptor binding and is reversible until another molecule reverse the process.

Question 9

Desensitization

Answer 9

Desensitization is a reversible process that can involve a reduction in the number of receptors expressed in the plasma membrane, inactivation of receptors, or changes in signaling proteins that mediate the downstream effect of the receptors. Homologous desensitization involves a reduction in the response only to the signaling molecule that caused the response (e.g., opioid dependence and tolerance), whereas heterologous desensitization is when one ligand desensitizes the response to another ligand.