bio > c2.1 chemical signalling > Flashcards

c2.1 chemical signalling Flashcards

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1
Q

ligand

A

molecule that binds selectively to a specific site on another molecule

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2
Q

how do ligands 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 neuron

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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
where are cytokines secreted from + where do they perform their function
almost all cells in the body acts on the cell that produced them/nearby cells
26
importances of cytokines [2]
important in the immune system and cell division
27
cytokines eg
interleukin
28
what are calcium ions used for [2]
1. muscle fibre- sarcoplasmic reticulum use calcium to initiate muscle contraction 2. neurones- use calcium to secrete neurotransmitters into the synapse
29
amines
compounds and functional groups that contain a basic nitrogen with a lone pair
30
steroid
organic compound with four fused rings arranged in a specific molecular configuration
31
how far do neurotransmitters have to travel for them to deliver their effect + where do they reach
small distance reach the postsynaptic neurone
32
how far do hormones have to travel for them to deliver their effect + how
greater distances carried in the bloodstream
33
where will LH from the pituitary gland travel to
testes/ovaries
34
how do acetylchloline receptors work
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
G-protein coupled receptors (GPCRs)
activates a second protein to pass on signals into the cell
36
what is the G-protein made up of
3 subunits (α, β and γ)
37
when is the G protein inactive
when GDP is bound to the α submit
38
what happens when a ligand binds to the receptor [2]
1. receptor changes shape 2. GDP detaches
39
how is the G protein activated
GTP bind + activate
40
what happens when the G protein is activated
changes inside the cell
41
what happens when the G protein is active
GTP-bound alpha subunit and the beta-gamma dimer will relay messages in the cell by interacting with other membrane proteins
42
2 types of activity triggered by G proteins
1. stimulation 2. inhibition
43
role of beta-gamma dimer
social messenger
44
what causes the different activities triggered by the G proteins
the receptor/the G protein
45
mechanism of adrenaline receptor (a GPCR) [4]
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
why is a second messenger needed
chemical signals cant go into the cell
47
what does tyrosine kinase do
add phosphate from ATP to the amino acid tyrosine in a protein
48
transmembrane receptors with tyrosine kinase activity eg
insulin receptor
49
how insulin receptor works [4]
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
can steroid hormones pass thru (hydrophobic)
yes
51
what do steroid hormones bind to + what do they form
bind to intracellular receptors in the cytoplasm forms hormone-receptor complex
52
mechanism of steroid hormones
1. enter the nucleus 2. attaches to DNA → promote gene transcription →particular polypeptide is produced
53
steroid hormones eg [3]
1. oestradiol 2. progesterone 3. testosterone
54
what happens w oestradiol before and during ovulation + product
binds to a receptor inside the cytoplasm of hypothalamus cell forms hormone-receptor complex
55
effect + mechanism of oestradiol to cells in the hypothalamus
mechanism- move to nucleus + act as a transcription factor effect- enhance the transcription of gonadotropin-releasing hormones in hypothalamus
56
effect of gonadotropin-releasing hormones
triggers release of LH and FSH from anterior pituitary gland
57
where is progesterone made
ovary
58
mechanism of progesterone
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
importance of insulin-like growth factor binding protein and Indian Hedgehog
important for growth and differentiation in endometrium to promote successful embryo implantation
60
eg regulation of cell signalling pathways by positive feedback
calcium-induced calcium release
61
eg regulation of cell signalling pathways by negative feedback [3 steps]
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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