c2.1 chemical signalling

Question 1

ligand

Answer 1

molecule that binds selectively to a specific site on another molecule

Question 2

how do ligands prevent other substances from binding [2]

Answer 2

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

Question 3

what other ways can the receptors make it fit

Answer 3

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

Question 4

what does binding of a signalling chemical to a receptor do

Answer 4

sets off a sequence of responses within a cell

Question 5

2 types of signalling chemicals + why

Answer 5

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

Question 6

location of chemicals that dont enter the cell

Answer 6

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

Question 7

location of receptor protein

Answer 7

extends across the membrane with a region extending into the cytoplasm

Question 8

what are receptor proteins known as

Answer 8

transmembrane receptors

Question 9

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

Answer 9

outside- hydrophilic amino acids
inside- hydrophobic amino acids

Question 10

location of receptor proteins for the chemicals that do go inside

Answer 10

in the cytoplasm/nucleus

Question 11

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

Answer 11

intracellular receptors

Question 12

intracellular receptors characteristics [2]

Answer 12

1. soluble
2. hydrophilic amino acids

Question 13

why do intracellular receptors have hydrophilic amino acids

Answer 13

remain dissolved in the aqueous fluid of the cytoplasm/nucleus

Question 14

how does the signalling molecule enter the cell

Answer 14

endocytosis

Question 15

how does quorum sensing in bacteria work

Answer 15

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

Question 16

what does it mean when the bacteria have sensed a quorum

Answer 16

a fixed number for an activity to go ahead

Question 17

quorum sensing in bacteria eg [2]

Answer 17

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

Question 18

where are hormones secreted form

Answer 18

endocrine glands

Question 19

where are hormones released into

Answer 19

bloodstream (might not stay in blood)

Question 20

eg of hormones [2]

Answer 20

1. testosterone
2. insulin

Question 21

where are neurotransmitters released from

Answer 21

presynaptic neurone

Question 22

when are neurotransmitters released

Answer 22

when action potential reaches the end of neuron

Question 23

eg of neurotransmitters [2]

Answer 23

1. acetylcholine
2. dopamine

Question 24

functional categories of signalling chemicals in animals [4]

Answer 24

1. hormones
2. neurotransmitters
3. cytokines
4. calcium ions

Question 25

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

Answer 25

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

Question 26

importances of cytokines [2]

Answer 26

important in the immune system and cell division

Question 27

cytokines eg

Answer 27

interleukin

Question 28

what are calcium ions used for [2]

Answer 28

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

Question 29

amines

Answer 29

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

Question 30

steroid

Answer 30

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

Question 31

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

Answer 31

small distance reach the postsynaptic neurone

Question 32

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

Answer 32

greater distances carried in the bloodstream

Question 33

where will LH from the pituitary gland travel to

Answer 33

testes/ovaries

Question 34

how do acetylchloline receptors work

Answer 34

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

Question 35

G-protein coupled receptors (GPCRs)

Answer 35

activates a second protein to pass on signals into the cell

Question 36

what is the G-protein made up of

Answer 36

3 subunits (α, β and γ)

Question 37

when is the G protein inactive

Answer 37

when GDP is bound to the α submit

Question 38

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

Answer 38

1. receptor changes shape 2. GDP detaches

Question 39

how is the G protein activated

Answer 39

GTP bind + activate

Question 40

what happens when the G protein is activated

Answer 40

changes inside the cell

Question 41

what happens when the G protein is active

Answer 41

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

Question 42

2 types of activity triggered by G proteins

Answer 42

1. stimulation 2. inhibition

Question 43

role of beta-gamma dimer

Answer 43

social messenger

Question 44

what causes the different activities triggered by the G proteins

Answer 44

the receptor/the G protein

Question 45

mechanism of adrenaline receptor (a GPCR) [4]

Answer 45

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)

Question 46

why is a second messenger needed

Answer 46

chemical signals cant go into the cell

Question 47

what does tyrosine kinase do

Answer 47

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

Question 48

transmembrane receptors with tyrosine kinase activity eg

Answer 48

insulin receptor

Question 49

how insulin receptor works [4]

Answer 49

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

Question 50

can steroid hormones pass thru (hydrophobic)

Answer 50

yes

Question 51

what do steroid hormones bind to + what do they form

Answer 51

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

Question 52

mechanism of steroid hormones

Answer 52

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

Question 53

steroid hormones eg [3]

Answer 53

1. oestradiol 2. progesterone 3. testosterone

Question 54

what happens w oestradiol before and during ovulation + product

Answer 54

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

Question 55

effect + mechanism of oestradiol to cells in the hypothalamus

Answer 55

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

Question 56

effect of gonadotropin-releasing hormones

Answer 56

triggers release of LH and FSH from anterior pituitary gland

Question 57

where is progesterone made

Answer 57

ovary

Question 58

mechanism of progesterone

Answer 58

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

Question 59

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

Answer 59

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

Question 60

eg regulation of cell signalling pathways by positive feedback

Answer 60

calcium-induced calcium release

Question 61

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

Answer 61

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