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bio > c2.1 chemical signalling > Flashcards

c2.1 chemical signalling Flashcards

1
Q

ligand

A

molecule that binds selectively to a specific site on another molecule

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2
Q

how do they prevent other substances from binding [2]

A

shape + chemical properties of the ligand and ligand-binding site has to match
- shape is specific
- chem: postive/negative

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3
Q

what other ways can the receptors make it fit

A

induce fit so ligand can fit on receptor
- change in shape is only temporary

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4
Q

what does binding of a signalling chemical to a receptor do

A

sets off a sequence of responses within a cell

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5
Q

2 types of signalling chemicals + why

A
  1. can enter the cells
  2. cant enter the cells
    - big + charged (polar)
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6
Q

location of chemicals that dont enter the cell

A

receptors- plasma membrane of target cell
binding site- facing the exterior

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7
Q

location of receptor protein

A

extends across the membrane with a region extending into the cytoplasm

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8
Q

what are receptor proteins known as

A

transmembrane receptors

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9
Q

where would he hydrophilic and hydrophobic amino acids be on the transmembrane receptors

A

outside- hydrophilic amino acids
inside- hydrophobic amino acids

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10
Q

location of receptor proteins for the chemicals that do go inside

A

in the cytoplasm/nucleus

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11
Q

what are the receptors responsible for the chemicals that do go inside called

A

intracellular receptors

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12
Q

intracellular receptors characteristics [2]

A
  1. soluble
  2. hydrophilic amino acids
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13
Q

why do intracellular receptors have hydrophilic amino acids

A

remain dissolved in the aqueous fluid of the cytoplasm/nucleus

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14
Q

how does the signalling molecule enter the cell

A

endocytosis

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15
Q

how does quorum sensing in bacteria work

A
  1. bacteria release a signalling molecule in a low rate to indicate population in the area
  2. when there is sufficient binding of signalling molecule to receptors in a cell → gene expression will change
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16
Q

what does it mean when the bacteria have sensed a quorum

A

a fixed number for an activity to go ahead

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17
Q

quorum sensing in bacteria eg [2]

A
  1. bacteria living symbiotically with deep sea animals will switch on bioluminescence and glow when they sense a high bacteria population when living inside sea animals
  2. bacteria on our teeth forms a biofilm when they have reached a high population
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18
Q

where are hormones secreted form

A

endocrine glands

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19
Q

where are hormones released into

A

bloodstream (might not stay in blood)

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20
Q

eg of hormones [2]

A
  1. testosterone
  2. insulin
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21
Q

where are neurotransmitters released from

A

presynaptic neurone

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22
Q

when are neurotransmitters released

A

when action potential reaches the end of it

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23
Q

eg of neurotransmitters [2]

A
  1. acetylcholine
  2. dopamine
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24
Q

functional categories of signalling chemicals in animals [4]

A
  1. hormones
  2. neurotransmitters
  3. cytokines
  4. calcium ions
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25
Q

where are cytokines secreted from + where do they perform their function

A

almost all cells in the body
acts on the cell that produced them/nearby cells

26
Q

importances of cytokines [2]

A

important in the immune system and cell division

27
Q

cytokines eg

A

interleukin

28
Q

what are calcium ions used for [2]

A
  1. muscle fibre- sarcoplasmic reticulum use calcium to initiate muscle contraction
  2. neurones- use calcium to secrete neurotransmitters into the synapse
29
Q

amines

A

compounds and functional groups that contain a basic nitrogen with a lone pair

30
Q

steroid

A

organic compound with four fused rings arranged in a specific molecular configuration

31
Q

how far do neurotransmitters have to travel for them to deliver their effect + where do they reach

A

small distance
reach the postsynaptic neurone

32
Q

how far do hormones have to travel for them to deliver their effect + how

A

greater distances
carried in the bloodstream

33
Q

where will LH from the pituitary gland travel to

A

testes/ovaries

34
Q

how to acetylchloline receptors work

A
  1. acetylcholine is released
  2. binds to the acetylcholine receptor (transmembrane receptor) on postsynaptic neurone → changes shape
  3. opens sodium channel
  4. positively charged sodium ions diffuses into postsynaptic neurone → changes membrane potential (causes depolarisation)
  5. new action potential starts
35
Q

G-protein coupled receptors (GPCRs)

A

activates a second protein to pass on signals into the cell

36
Q

what is the G-protein made up of

A

3 subunits (α, β and γ)

37
Q

when is the G protein inactive

A

when GDP is bound to the α submit

38
Q

what happens when a ligand binds to the receptor [2]

A
  1. receptor changes shape
  2. GDP detaches
39
Q

how is the G protein activated

A

GTP bind + activate

40
Q

what happens when the G protein is activated

A

changes inside the cell

41
Q

what happens when the G protein is active

A

GTP-bound alpha subunit and the beta-gamma dimer will relay messages in
the cell by interacting with other membrane proteins

42
Q

2 types of activity triggered by G proteins

A
  1. stimulation
  2. inhibition
43
Q

role of beta-gamma dimer

A

social messenger

44
Q

what causes the different activities triggered by the G proteins

A

the receptor/the G protein

45
Q

mechanism of adrenaline receptor (a GPCR) [4]

A
  1. adrenaline binds to adrenaline receptor → changes its shape + activates a G protein
  2. G protein activates adenylyl cyclase → breaks ATP in the cytoplasm to cyclic AMP (cAMP)
  3. cAMP acts as a second messenger → triggers a sequence of responses within the cell to enable fight or flight response
  4. eventually activates an enzyme (glycogen phosphorylase) to break down glycogen into glucose in liver cells)
46
Q

why is a second messenger needed

A

chemical signals cant go into the cell

47
Q

what does tyrosine kinase do

A

add phosphate form ATP to the amino acid tyrosine in a protein

48
Q

transmembrane receptors with tyrosine kinase activity eg

A

insulin receptor

49
Q

how insulin receptor works [4]

A
  1. insulin binds to receptor on plasma membrane → changes shape of receptor
  2. 2 tyrosine kinases at the tail forms a dimer → phosphorylates each other
  3. starts a sequence of events that ends with vesicles containing glucose transporters to move to plasma membrane
  4. so glucose diffuses into the cell faster
50
Q

can steroid hormones pass thru (hydrophobic)

A

yes

51
Q

what do steroid hormones bind to + what do they form

A

bind to intracellular receptors in the cytoplasm
forms hormone-receptor complex

52
Q

mechanism of steroid hormones

A
  1. enter the nucleus
  2. attaches to DNA → promote gene transcription →particular polypeptide is produced
53
Q

steroid hormones eg [3]

A
  1. oestradiol
  2. progesterone
  3. testosterone
54
Q

what happens w oestradiol before and during ovulation + product

A

binds to a receptor inside the cytoplasm of hypothalamus cell
forms hormone-receptor complex

55
Q

effect + mechanism of oestradiol to cells in the hypothalamus

A

mechanism- move to nucleus + act as a transcription factor
effect- enhance the transcription of gonadotropin-releasing hormones in hypothalamus

56
Q

effect of gonadotropin-releasing hormones

A

triggers release of LH and FSH from anterior pituitary gland

57
Q

where is progesterone made

A

ovary

58
Q

mechanism of progesterone

A
  1. diffuse into cells of endometrium
  2. bind to intracellular receptors to form hormone-receptor complex
  3. enter the nucleus
  4. acts as transcription factor for several genes
59
Q

importance of insulin-like growth factor binding protein and Indian Hedgehog

A

important for growth and differentiation in endometrium to promote successful embryo implantation

60
Q

eg regulation of cell signalling pathways by positive feedback

A

calcium-induced calcium release

61
Q

eg regulation of cell signalling pathways by negative feedback [3 steps]

A
  1. hypothalamus releases GnRH → stimulates LH release in anterior pituitary gland
  2. LH stimulates Leydig cells in testes to release testosterone
  3. increased testosterone level signals hypothalamus to stop releasing GnRH + anterior pituitary gland to stop releasing LH
    = end product inhibits its own production

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