Cell Communication

Question 1

Communication requirements

Answer 1

Ligand - signaling molecule
Receptor protein - molecule to which the receptor binds

Question 2

Receptor types

Answer 2

1. Intracellular - in cytoplasm - slow
2. Cell surface - in plasma membrane - fast

Question 3

Mechanisms for cellular communication

Answer 3

1. autocrine - signals to themselves
2. paracrine - cells are close by
3. endocrine - cells are at a distance
4. direct contact - gap junctions/plasmodesmata

Question 4

Intracellular receptors

Answer 4

Steroid hormones (derived from cholesterol)
- act as regulators of gene expression (transcription factors)

Question 5

3 subclasses of membrane receptors

Answer 5

1. ligand gated ion channel
2. G protein coupled receptor
3. enzymatic receptors

Question 6

1. Ligand gated ion channel

Answer 6

A pore responsive to a particular ligand that opens the channel to certain ions; common in neurons

Question 7

2. G protein-coupled receptor

Answer 7

When a ligand binds to such a receptor, GDP is exchanged for GTP which causes the alpha subunit to dissociate from the beta and gamma subunits. Either of the two subunits causes changes in the cell; examples are epinephrine, olfactory receptors, etc.

Question 8

3. Enzyme linked receptor

Answer 8

When a ligand binds to receptor tyrosine kinase (RTK), they dimerize and autophosphorylate (protein kinase), causing a downstream cascade of cellular response. Phosphatases remove the phosphate groups, inhibiting cellular response.
Important role in the working of cancer.