cell signalling

Question 1

name signalling molecules

Answer 1

hormones
cytokines
growth factors
neurotransmitters

Question 2

what is autocrine signalling

Answer 2

when a cell signals to itself by releasing a ligand that binds to receptors on itself

Question 3

what are the types of cell to cell signalling?

Answer 3

autocrine
endocrine
paracrine - ligand binds to local cells
contact-dependent - ligand bound to surface so it has to get into contact with the cell to signal
synaptic

Question 4

explain the three stages of cell signalling

Answer 4

reception - ligand binds to target receptor
transduction - signal is relayed, amplified and modified by signalling proteins
response - target proteins in the cell perform actions that change cell behaviour

Question 5

how can the same signalling molecule produce different response in different cells?

Answer 5

different receptor type

different internal machinery

Question 6

what are the different types of receptors?

Answer 6

intracellular

cell surface - g protein linked, ion channel linked and enzyme linked

Question 7

how do ion channel-coupled receptors work?

Answer 7

ligand binds to the receptor extracellularly and opens the channel. ions flow into the cell

Question 8

give an example of an ion channel-coupled receptor

Answer 8

nicotinic ACh receptor

ACh binds and allows Na+ to enter

Question 9

explain how GPCRs work

Answer 9

7 pass transmembrane receptor linked to a G protein with 3 subunits

becomes activated when GDP is replaced by GTP

alpha and beta subunits dissociate to interact with enzymes or ion channels to induce a response

stays activated until the GTP is hydrolysed

Question 10

explain how a RTK works?

Answer 10

ligand binding causes dimerisation of the two tyrosine kinase subunits

activates kinase domain

phosphorylate each other

intracellular proteins bind and elicit action

Question 11

how do intracellular receptors work?

Answer 11

hormone enters the cell and gets into the cytoplasm or into the nucleus. binds to receptor and forms a complex. interacts with the DNA and alters gene expression and cell function

Question 12

what does a 2nd messenger do?

Answer 12

amplifies the original signal to downstream messenger molecules

Question 13

name some second messenger

Answer 13

cAMP
Ca2+
IP3

Question 14

how is cAMP generated?

Answer 14

from ATP by adenylyl cyclase

Question 15

how does cAMP work?

Answer 15

activates protein kinase A which is phosphorylated and activates downstream signalling proteins

Question 16

how is cAMP degraded?

Answer 16

phosphodiesterase

Question 17

how can calcium enter the cytosol?

Answer 17

from the extracellular space via channels

from stores in the ER

Question 18

how does calcium act as a second messenger?

Answer 18

when it binds to proteins such as calmodulin to activate various signalling proteins

Question 19

what is a molecular switch?

Answer 19

molecules that can be reversibly switched between two stable states by a trigger

Question 20

what is the mechanism by which intracellular signalling proteins can act as a molecular switch?

Answer 20

phosphorylation or dephosphorylation

Question 21

what is the trigger for intracellular signalling proteins to act as a molecular switch?

Answer 21

kinase - activates it

phosphatase - removes the phosphate group