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YEAR 2 S1 BIOCHEM > Ian receptors and cell signalling > Flashcards

Ian receptors and cell signalling Flashcards

1
Q

survival signals are generated by what what type of cell signalling?

A

cell cell contact

- esp with ECM and through adherence junctions

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2
Q

grow and divide signals are generated by what what type of cell signalling?
what are exceptions?

A
  • tends to be PARACRINE

- exceptions are Growth Hormone, Oestrogen and Testosterone

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3
Q

differentiate signals are generated by what what type of cell signalling?

A
  • local progenitor cells are the ones that have the abilityt to still divide
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4
Q

apoptosis signals are generated by what what type of cell signalling?

A
  • extrinsic or intrinsic pathway
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5
Q

describe contact dependent signalling?

A
  • molecules on the surface of one cells are recognised by receptors onthe adjacent cell
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6
Q

describe paracrine signalling? give 3 examples

A

signal released from a cell has an effect on neighbouring cell

  • fibroblast growth factor (prolif and diff)
  • transforming growth factor (growth, diff, prolif, apoptosis)
  • Wnt signalling (embroyo)
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7
Q

what is chemotaxis?

A

movement of an immune cell along a concentration gradient

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8
Q

describe synaptic signalling?

A

nerve cells release the signal (NT) which binds to receptors on nerby cells

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9
Q

why can it take even days for the function of a cell to change?

A

function is dictated by the proteins within the cell

  • proteins will remain until they are degraded
  • O they remain doing their function until they are degraded
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10
Q

describe endocrine signalling?

A
  • hormones released act on other cells throughout body
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11
Q

give examples of how the same NT can have different effects depending on which target it is acting on

A
  • Acetylcholine
    heart: acts on muscarinic receptors and causes a descrease in rate and force of contraction
    skeletal muscle cell: causes contraction
    salivary gland: granulation and release of saliva and enzymes
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12
Q

which 2 enzymes are used in virtually all signalling pathways?

A

kinases and phosphatases

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13
Q

give an example of a kinase?

how does it work?

A

serine or serine-threonine kinase

  • a phosphate is taken from ATP by the kinase and added to the protein
  • phosphate is a -vely charged molecule O will affect aa R groups (pull away or closer so shape of mol changes)
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14
Q

what is a secondary messenger?

A

they diffuse into the cell and activate other proteins

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15
Q

give an example of a secondary messenger

A

eg cAMP

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16
Q

what makes cAMP?

A

adenylate cyclase

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17
Q

what does GEF stand for?

A

Guanine nucleotide exchange factor

18
Q

what does GAP stand for?

A

GTPase accelerating protein

19
Q

do all cells have the same intracellular signalling mechanisms?

A

yes, the parts that are different are the receptor at the top and effector protein at the bottom

20
Q

what is the function of cAMP?

A

it activates protein kinase A

21
Q

cGMP is made by what? what is its function?

A

guanylate cyclase

function: activate protein kinase G

22
Q

how is protein kinase C activated?

A
  • Phospholipase C takes a phosphatidylinositol-bisphosphate and REMOVES THE HEAD GROUP leaving behind DIACYLGLYCEROL
  • hydrophilic head group (INOSITOL-TRISPHOSPHATE) DIFFUSES INTO CELL
  • binds intracellular receptors (IP3 receptors) on SER
  • IP3 receptors are CALCIUM channels and allow Ca release into cytoplasm
  • at membrane: DIACYLGLYCEROL binds to PROTEIN KINASE C, making it partially active
  • once the Ca released reaches PROTEIN KINASE C it becomes SUPERACTIVE
23
Q

where is protein kinase A and protein kinase G found?

A

they are soluble and exist in cystoplasm

24
Q

where is protein kinase C found?

A

in the membrane

25
Q

describe how extracellular signals are amplified

A
  • a SINGLE/small amount of signalling molecule which binds to a small number of receptors
  • to AMPLIFY signal, the receptors activate for eg anenylate cyclase which go on to activate a MUCH GREATER NUMBER of cAMP
  • the cAMP activates a greater number of enzymes, thus forming a greater amount of PRODUCT
26
Q

describe an ion channel

A
  • ligand gated hole in the membrane

- opens in response to an agonist

27
Q

what are the 2 ways in which a hole can be formed in a membrane? what kinds of proteins form these channels?

A
  • barrel of beta sheets
  • single transmembrane/ multi-transmembrane domains ALPHA helices

formed from MULTIMERIC PROTEINS (quarternery proteins)( 3, 5 or 7 subunits)

28
Q

GABA A and nicotinic Ach receptors have how many subunits?

A
  • 5 subunit

- each subunit has 4 transmembrane domains

29
Q

how do GABA A and nicotinic Ach receptors work?

A
  • ligand binds

- protein conformation changes, ligand can O enter

30
Q

how is variation in how tissues respond to the same NT created?

A
  • DIFFERENT SUBUNIT expression
31
Q

why are G protein coupled receptors so important?

A

because ~70% of drugs are made to bind to a G protein coupled receptor

32
Q

G protein coupled receptors all share what?

A
  • all have a TERTIARY protein receptor with 7 transmembrane domains
  • TRIMERIC G protein ( three parts- alpha, beta-gamma, target enzyme)
33
Q

responses to activation of ion channel receptors tend to be what?

A

rapid, immediate changes

34
Q

what is a metabotropic receptor?

A

a membrane receptor that acts through a SECONDARY messenger

35
Q

how do G protein coupled receptors work?

A
  • receptor activated when ligand BINDS
  • receptor chages SHAPE
  • shape change transmitted THROUGH the membrane to G protein alpha subunit which also changes shape
  • GDP is exchanged for GTP
  • G protein DISSOCIATES and becomes FUNCTIONAL
  • GTP BINDS to ALPHA subunit, and it diffuses within membrane and affects activity of target enzyme (activate or inhibit)
36
Q

the N terminus and C terminus of the receptor are found WHERE

A

N terminus is EXTRACELLULAR

C terminus is INTRACELLULAR

37
Q

the extracellular loops are called E1,2,3 etc, which loops does the ligand attach to?

A

E2 or E3

38
Q

the intracellular (cytosolic) loops are called C1,2,3 etc, which loops does the G protein attach to?

A

C3 or C4

39
Q

which subunits of the G protein are able to be attached to the membrane?

A

alpha and gamma (with beta inside it)

40
Q

where is the beta subunit found?

A

INSIDE the gamma subunit, they function as one, they are never separate

41
Q

which G protein subunit has a GTPase function?

A

only ALPHA subunit

beta-gamma subunit can act as INHIBITORY subunit

42
Q

how are effector proteins associated with G protein coupled receptors ACTIVATED?

A

-

YEAR 2 S1 BIOCHEM (2 decks)

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