Examples of cellular responses to signals

Question 1

what is an important part of cell-to-cell communication?

Answer 1

the release of signal molecules

Question 2

how are water soluble molecules released?

Answer 2

released from vesicles via regulated exocytosis

Question 3

how are lipid soluble molecules released?

Answer 3

released by diffusion as soon as they are synthesized

Question 4

what happens in the golgi body?

Answer 4

vesicles are generated by the Golgi and tagged to specific destinations
these include the cell surface where they release their contents by exocytosis

Question 5

what is constitutive regulation?

Answer 5

extracellular matrix materials

Question 6

what are regulated regulations?

Answer 6

signals (paracrine, endocrine and neuronal)

Question 7

what in the function of vessicle associated proteins?

Answer 7

-building the vesicle
-loading of signal molecules into the vesicle
-guiding the vesicle to the correct location
-regulating exocytosis
-vesicle recovery after exocytosis

Question 8

how do SNARES and Rabs work?

Answer 8

interact with each other to bring the vesicle into the right place.
They also twist together to keep the vesicle in place

Question 9

what happens when the vesicle gets to the correct site?

Answer 9

exocytosis

Question 10

what proteins are involved in getting the vesicle to the correct place?

Answer 10

SNARES and Rabs

Question 11

what is synaptotagmin?

Answer 11

protein involved in exocytosis of vesicles
- makes exocytosis Ca2+ dependent

Question 12

how does synaptotagmin make exocytosis Ca2+ dependent?

Answer 12

Ca2+ binding to synaptotagmin changes its shape bringing the vesicle towards the cell membrane

thus for regulated exocytosis to occur a cell must increase its Ca2+ concentration at the site of release

Question 13

where are adrenal chromaffin cells found?

Answer 13

within the adrenal medulla

Question 14

what is the function of adrenal chromaffin cells?

Answer 14

releases catecholamines (adrenaline and noradrenaline) in response to stress

Question 15

what stimulates the secretion of catecholamines from adrenal chromaffin cells?

Answer 15

secretion is stimulated by acetylcholine release from nerve

Question 16

how does acetylcholine stimulate adrenal chromaffin cells?

Answer 16

-activates nicotine acetylcholine receptor
-the receptor channel opens and Na+ influxes
-cell depolarizes and opens voltage-gated Ca2+ channels
-Ca2+ influx also causes exocytosis
-Ca2+ can also stimulate tyrosine hydroxylase (TH) to make replacement catecholamines

Question 17

where are beta cells of the pancreas found?

Answer 17

found within the islets of Langerhans

Question 18

what is the function of pancreatic beta cells?

Answer 18

release insulin in response to increased glucose concentration in the blood

Question 19

how are beta cells signalled to produce insulin?

Answer 19

-glucose is transported into the beta-cell
-then metabolized to form ATP
-ATP acts to close a K+ channel
-more +ve charge within the cell causes it to depolarize
-opens voltage-gated Ca2+ channels
-Ca2+ enters the cell
-stimulates exocytotic release of insulin
-also increases insulin synthesis
-insulin acts on insulin receptors to remove glucose from the blood into cells

Question 20

what are mast cells?

Answer 20

cells of the immune system found within connective tissue

Question 21

what is the structure of mast cells?

Answer 21

contain multiple granules (vesicles)

Question 22

what is mast cell degranulation?

Answer 22

Massive exocytosis called degranulation

Question 23

what is the function of mast cells?

Answer 23

-release a cocktail of biologically active molecules
-provide first-line of defense to foreign antigens, tissue damage and pathogens

Question 24

how are mast cells signaled to undergo degranulation?

Answer 24

-allergens cross-link two IgE (FcR1) receptors
-trigger a pathway that releases Ca2+ from the endoplasmic reticulum
-increased Ca2+ causes degranulation
-receptor activation also activates other intracellular pathways that increases production of more cytokines