Lecture 11: Cell communication 1

Question 1

Know the four essential elements of cell communication

Answer 1

1. Signaling cell
2. Signaling molecule
3. Receptor molecule
4. Receptor cell

Question 2

Know and describe the four steps in cell signaling

Answer 2

1. receptor activation:
2. signal transduction:
   - signal is transmitted to the interior of cell by signal transduction pathway.
3. Response
4. Termination

Question 3

• Know, describe and compare the four classes of cell signaling

Answer 3

Endocrine signalling:
- signalling involving a molecule that travels through the bloodstream (over large distances) ie) testoterone, estrogen.

Paracrine Signalling:

• Signalling through diffusion of signalling molecule (over short distance).
• These cells are in close proximity of each other.

Autocrine Signalling:
- Signalling in which the signalling cell and responding cell are the same cell. ie) development of embryo.

Juxacrine Signalling:

• Signalling occurs by direct cell contact.
• a transmembrane protein on the surface of cells acts as the signalling molecule.

Question 4

Ligand and ligand binding site?

Answer 4

Ligand: Signalling molecule

Ligand binding site: location on the receptor to which the ligand binds.

• Binding of a ligand to its’ binding site on a receptor causes a
conformational change in the receptor that triggers chemical reactions

Question 5

• Know, describe and compare polar molecules and cell-surface
receptors to nonpolar molecules and intracellular receptors

Answer 5

• Polar signalling molecules cannot cross the plasma membrane and rely on cell-surface receptors.
• Small non-polar molecules can freely pass through the plasma membrane and activate cytoplasmic receptors.