Cell signalling

Question 1

What are 5 types of communication?

Answer 1

1. Endocrine
2. Paracrine
3. Autocrine
4. Signalling between membrane attached proteins
5. Neurotransmission

Question 2

What is endocrine comm?

Answer 2

Targeting distant cells through the blood stream (hormones) e.g. glucagon stimulating glycogenolysis and gluconeogenesis in the liver

Question 3

What is paracrine comm?

Answer 3

Targeting nearby cells e.g. insulin inhibiting glucagon secretion

Question 4

What is autocrine signalling?

Answer 4

Signalling molecule acts on the same cell. For example a cell infected with a virus can tell itself to undergo apoptosis.

Question 5

What is signalling between membrane attached proteins?

Answer 5

Interactions between plasma membrane proteins on adjacent cells.

Question 6

4 steps of neurotransmission

Answer 6

1. Propagation of action potential through opening of voltage gated sodium ion channels. This causes an influx of sodium ions causing membrane depolarisation, opening VGSCs further along. Repolarisation occurs through the opening of voltage gated potassium ion channels and closing of sodium ion channels in order to prevent the action potential from travelling backwards.
2. At the synapse, the action potential causes voltage gated calcium ion channels to open at the presynaptic terminal. The influx of calcium ions cause vesicles containing neurotransmitter to fuse with the presynaptic membrane releasing the neurotransmitter into the synaptic cleft.
3. The postsynaptic receptors are activated on the postsynaptic membrane.
4. This causes depolarisation of the postsynaptic neurone inducing an action potential or hyperpolarisation of the postsynaptic neurone reducing the chance of an action potential being induced depending on the ions involved (whether sodium ion channels or chloride ion channels are opened when the neurotransmitter binds to postsynaptic receptors).

Question 7

What are the 4 different types of receptors?

Answer 7

1. Ionotrophic
2. G-protein coupled receptor
3. Enzyme-linked receptor
4. Intracellular receptor

Question 8

Ionotrophic receptor?

Answer 8

ligand binding causes ion channel to open allowing influx of ions which can increase or decrease the likelihood an action potential will fire depending on the charge of the ions moving into the neurone.

Question 9

G-protein coupled receptor?

Answer 9

ligand binding causes the shape of the receptor to change. G-protein with GDP is off and GTP on. Therefore, when the receptor changes shape it can exchange the GDP for GTP thus activating the G-protein. The G-protein then disassociated into its other two components alpha G-GTP and beta gamma G which can activate different signalling cascades. GTPase acts on the alpha-GTP subunit cleaving the phosphate off GTP inactivating the protein. The receptor remains active if the ligand remains bound. In the resting state, the G-protein complex is normally associated to the receptor, and after the ligand binds, the g-protein disassociates.

Question 10

Enzyme linked receptor?

Answer 10

Ligand binding causes receptors to cluster, activating enzyme activity within the cytoplasm. The enzymes phosphorylate the receptor causing signalling proteins to bind to the cytoplasm recruiting other signalling proteins thus generating a signal within the cell.

Question 11

Intracellular receptor?

Answer 11

Thyroid and steroid hormones target intracellular receptors in the cytoplasm or nucleus of cell. These hormones must be able to readily diffuses through the phospholipid bilayer of the cell to reach the intracellular receptor. For example, steroid hormones are derived from cholesterol and therefore can readily diffuse across.