Cell Communication

Question 1

Main principles of cell signalling (6)

Answer 1

1) Synthesis or release of ligand by signal sending cell

2) Ligand delivery and binding to specific receptor of signal receiving cell

3) Receptor activation and signal relay

4) Relay of signals by intracellular signalling proteins

5) Activation of target protein and cellular response through transcription factors and gene expression

6) Termination of signal by decreasing levels of ligands/receptors

Question 2

Paracrine Signalling

Answer 2

used to communicate with nearby cells

Question 3

Endocrine Signalling

Answer 3

endocrine cells of glands secrete signalling molecules into the circulatory signal

Question 4

Contact-dependent Signalling (3)

Answer 4

• Cells use membrane bound proteins as ligands
• which directly binds with the cognate receptors of other cells
• whilst still bound to the cell

Question 5

Autocrine Signalling

Answer 5

cells express both the ligand and receptor to self-stimulate themselves

Question 6

3 subunits of G-protein

Answer 6

alpha, beta, lamda

Question 7

G-protein in resting state

Answer 7

alpha subunit bound to GDP

Question 8

G-protein in active state (2)

Answer 8

• alpha subunit bound to GTP
• dissociated from beta and lama

Question 9

3 types of G-protein (3)

Answer 9

Gq, Gs, Gi

Question 10

What does Gq activate?

Answer 10

Phospholipase C
(PLC)

Question 11

What does Gs activate?

Answer 11

Adenylyl Cyclase
(AC)

Question 12

Activated Gs pathway

Answer 12

• activates AC
• with +ATP
• activates cAMP
• activates PKA

Question 13

Activates Gq pathway

Answer 13

• activates PLC
• activates PIP2
• forms DAG + IP3
• DAG activates PKC
• IP3 increases Calcium ions

Question 14

Controlling acid secretion by stomach cells (4)

(GPCR signalling example)

Answer 14

1) endocrine cell releases Histamine

2) Histamine binds to H2 receptors and G-protein on gastric cell

3) AC to cAMP to PKA

4) H-K transporter releases H+

Question 15

Regulating water movement in intestinal cells (4)

(GPCR signalling example)

Answer 15

1) Neurone releases vasoactive intestinal peptide (VIP)

2) Vasoactive intestinal peptide (VIP) binds to VIP receptor and Gs-protein on intestinal cell

3) AC to cAMP to PKA

4) Cl- channel releases Cl-which then encounters Na+ and H2O

Question 16

Corruption of G-protein and diarrhoea (4)

(GPCR signalling example)

Answer 16

1) Cholera toxin attaches ADP-ribose to alpha subunit

2) G-protein remains active as GTP cannot be hydrolysed

3) Continuous signal relay causes increased activation of adenylyl cyclase and cAMP production

4) More Cl- leading to water