Cell signalling

Question 1

What is intercellular communication important for?

Answer 1

• Essential for homeostasis.
• Regulate growth + division.
• Facilitate tissue development + organisation.

Question 2

What are the 3 intercellular communication pathways?

Answer 2

1. Membrane receptors.
2. Intracellular receptors.
3. Gap junctions.

Question 3

What are gap junctions?

Answer 3

These are specialised regions where cells connect and communicate via small charged particles.

Question 4

What are membrane receptors?

Answer 4

Proteins on cell surfaces that interact with signalling molecules, initiating intracellular activities in response to external signals.

Question 5

What are intracellular receptors?

Answer 5

Proteins inside cells that respond to specific signalling molecules by modulating gene expression.

Question 6

What are the 4 chemical communication pathways?

Answer 6

1. Endocrine signalling.
2. Paracine signalling.
3. Autocrine signalling.
4. Plasma membrane attached proteins signalling (Juxtacrine signalling)

Question 7

What is ‘Plasma membrane attached proteins signalling’ (Juxtacrine signalling)?

Answer 7

A type of contact-dependent signalling. There is no release of signalling molecules in the extracellular fluid. The signalling molecules remain bound to the cell surface and act as ligands.

Question 8

What is ‘endocrine signalling’?

Answer 8

Hormones are secreted into the bloodstream by an endocrine gland and will act on target cells.

Question 9

What is ‘paracine signalling’?

Answer 9

Signalling molecules are released by cells in the extracellular space and act locally on nearby target cells.

Question 10

What is ‘autocrine signalling?

Answer 10

The signalling molecules act on the same cell that produces them.

Question 11

Compare and contrast ‘Endocrine’ and ‘Paracine’ signalling.

Answer 11

Endocrine -
1. Signalling molecules = hormones
2. Slow because of diffusion + blood flow.
3. Hormone concentration is greatly diluted because of the distribution within the blood vessel.
4. Specificity is based on the fact that each endocrine cell secrete a hormone that is recognised by certain target cell receptors.

Paracrine -
1. Signalling molecules = neurotransmitters.
2. Faster + precise due to quick diffusion between axon terminal and target cell.
3. Neurotransmitter concentration is much higher.
4. Specificity of action results from synaptic contact of a neuron with specific target cells.