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BIOSCI 107 > (02) Cell Communication > Flashcards

(02) Cell Communication Flashcards

1
Q

how do cells communicate

A

often by chemical signals
(but can also be light, taste, smell etc)

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2
Q

two types of secreted signals

A

local signalling
long distance signalling

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3
Q

two types of local signals

A

Paracrine - eg. fibroblast growth factors
Synaptic - eg. neurotransmitters (acetylcholine - ACh)

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4
Q

example of long distance signalling

A

hormones (=endocrine signalling) produced by specialised cells travel via circulatory system to act on specific cells
eg. insulin

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5
Q

name the three steps of cell signalling

A

Reception
Transduction
Response

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6
Q

describe general processes involved in Reception

A

signalling protein (primary messenger) binds to receptor protein
–> shape / chemical change in receptor protein

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7
Q

describe general processes involved in the transduction stage of cell signalling

A

altered receptor protein activates another protein, causing a relay of changes
(via relay molecules (=second messengers))

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8
Q

what is a phosphorylation cascade

A

think about phosphorylation as a way that cells send signals (its a very general term)

so a phosphorylation cascade is a series of changes via phosphorylation in activated proteins in the transduction phase

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9
Q

describe the process involved in the response phase of cell signalling

A

all the activated proteins cause one or more functions to occur in the cell
(basically, something actually happens)

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10
Q

name the two main types of receptors

A

Intracellular receptors - located in cytoplasm of cell
Membrane-bound / cell surface receptor - attached to membrane

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11
Q

features of primary messengers of intracellular receptors

A

signalling protein / primary receptor is generally hydrophobic and/or small
lipid soluble, can enter cell

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12
Q

examples of intracellular signalling proteins

A

Testosterone
estrogen
progesterone
thyroid hormones

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13
Q

describe the features of primary messengers for membrane-bound / cell surface receptors

A

primary messenger is generally hydrophilic and/or large

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14
Q

what type of cell signalling is most common?

A

membrane-bound / cell surface receptors are most common
intracellular receptors are less common

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15
Q

examples of membrane-bound / cell surface receptor proteins

A

G Protein Coupled Receptor
receptor tyrosine kinase (this is probably cell surface bc we don’t cover in detail)
ligand-gated ion channel

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16
Q

what are GPCRs

A

G-protein coupled receptors
Transmembrane proteins that pass the plasma membrane 7 times

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17
Q

function of GPCRs

A

hundreds of different types exist, so they have VERY DIVERSE FUNCTIONS

18
Q

what do GPCRs couple with and what is its function?

A

GPCRs couple with G proteins, which are MOLECULAR SWITCHES
(bound to GDP = off, bound to GTP = on)

19
Q

stages of activating enzyme through GPCR

A

at rest, GPCR unbound, G protein bound to GDP, enzyme inactive
ligand binds receptor, and binds G protein. GTP displaces GDP. (enzyme remains inactive)
activated G protein dissociates from receptor and elevates enzyme (=cellular response)
G protein has GTPase activity, release from enzyme, back to resting state

20
Q

describe the structure of a ligand gated ion channel

A

receptor in plasma membrane has a channel (“gate”)
binding ligand at receptor site –> change in shape –> open closes channel

21
Q

what is the function of a ligand gated ion channel

A

ions (eg. Na+, K+ etc) can pass through

22
Q

define ligand

A

signalling molecule that binds SPECIFICALLY to another protein

23
Q

process of ligand gated ion channels

A

at rest, ligand unbound, gate closed
ligand binds, gate opens, SPECIFIC ions flow into cell (causing cell response)
ligand dissociates, gate closes

24
Q

what body system relies heavily on ligand gated ion channels?

A

the nervous system!
released neurotransmitters bind as ligands to ion channels on target cells to propagate action potentials

25
Q

what are protein kinases?

A

enzymes that transfer a phosphate group from ATP to another (specific) protein (activates it)

26
Q

what are phosphatases?

A

enzymes that dephosphorylate (remove phosphate) so the protein is inactive but recyclable
-ase = destroy

27
Q

what is a second messenger?

A

another small molecule included in the phosphorylation cascade
between the main enzyme in the PM and the first protein kinase

28
Q

examples of second messengers

A

cAMP
Ca2+ ions

29
Q

what is the enzyme activated by GPCR?

A

adenylyl cyclase

30
Q

what does adenylyl cyclase convert ATP to

A

converts ATP to cAMP (which then acts as a second messenger in the phosphorylation cascade)

31
Q

describe the differences in Ca ion concentration inside and outside the cell

A

LOW Ca2+ inside the cell
HIGH Ca2+ outside the cell (over 1000x higher)

32
Q

how is Ca ion concentration maintained?

A

via calcium pumps, located
- out of cell
- into ER
- into mitochondria

33
Q

How is GPCR signalling linked to Ca2+ signalling?

A

G protein activates the protein phospholipase C, which cleaves PIP2 (phospholipid) into DAG and IP3

IP3 (2nd messenger) diffuses through cytosol, bonds to a gated channel in ER
Ca ions flow out of ER, activated other proteins

G protein –> phospholipase C + PIP2 –> (DAG +) IP3 –> gated channel –> Ca2+

34
Q

two reasons why there are many steps in cell signalling

A

AMPLIFICATION (of response)
multiple control points
specificity of response (spatial / temporal)
coordination w/ other signalling pathways

35
Q

what is cell response + example

A

transduction of signal leads to activation / regulation of one or more cell activities

GENE EXPRESSION

36
Q

how are cell signals turned off?

A

cAMP (2nd messenger) is broken down by phosphodiesterase (PDE)

(eg. caffeine blocks PDE)

37
Q

cell signal processes involved in generating a lot of ATP quickly

A

glycogen –> glucose 1-phosphate –> glucose 6-phosphate, used in glycolysis to generate ATP

Adrenalin acts through GPCR, activates cAMP + 2 protein kinases in phos cascade
MASSIVE amplification

38
Q

Is phospholipase C a membrane bound or peripheral enzyme?

A

peripheral

39
Q

IP3 gated Ca channels are located on the:

A

endoplasmic reticulum lumen

40
Q

IP3 diffuses where?

A

in cytosol
before binding to an ion gated channel in ER

41
Q

phospholipase C cleaves…

A

PIP2 (phospholipid) –> DAG + IP3

BIOSCI 107 (22 decks)

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