Question

1. Explain the four types of cell signaling with some examples.

2. Explain the two classes of extracellular signal molecules and receptor types. Why does the receptor location differ? Include some examples for each class.

3. Explain how NO works.

4. Explain the general mechanism and function of intracellular signaling pathways.

5. Review molecular switches and the two classes which repeats earlier information on how protein activity can be regulated.

Answer 1

1. Autocrine Signaling: Here releser is itself responder. Cells produce signals, those the signals are released and bind on the receptor of target cell (itself). E.g. immune system: B cells release IL-2 and it binds to their own receptor. That B cell strats clonal formation.

Paracrine Signaling: Cells which are in near vicinity of releser cell show this response as it depends upon the concentration of signaling molecules. E.g. Signaling by nitric oxide: vasodialation occurs where NO concentration is high.

Juxtracrine Signaling: Contact dependent cell signaling. Adjacent (touching) cells of the releaser cells receive the signals transmitted via cell-cell or cell - extracellular matrix signalling. E.g. Delta-Notch signaling pathway.

Endocrine Signaling: It is a long distance communication where a medium of travel is necessary. Concentration of signal should be very high. E.g. Hormones are dumped into blood and then carried throughout the body. Where appropriate receptor is present signaling molecules bind and then respond.