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1.4 : communication and signalling Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

how do multicellular organisms signal between molecules

A

through extracellular signalling molecules

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2
Q

examples of signalling molecules

A

steroid hormones, peptide hormones, neurotransmitters

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3
Q

what are receptor molecules

A

receptor molecules are proteins with a binding site for a specific molecule

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4
Q

what does the binding of the receptor change

A

changes the conformation of the receptor which initiates a response in the cell

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5
Q

signal specificity

A

different cell types produce different signals that can only be detected and responded by cells with the specific receptor

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6
Q

why do signalling molecules have different effects on different cell types

A

will have different effects due to differences in intracellular signalling molecules and the pathways involved

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7
Q

what will different cell types show in response to the same signal

A

a tissue specific response

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8
Q

hydrophobic

A

molecules that are seemingly repelled by large masses of water. these molecules are also known as non-polar

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9
Q

hydrophobic signalling molecules movement

A

diffuse directly through phospholipid bi layer of membrane and bind do intracellular receptors

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10
Q

what are the receptors for hydrophobic molecules

A

transcription factors

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11
Q

what are transcription factors

A

transcription factors proteins that when bound to DNA can either stimulate or inhibit initiation of transcription.

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12
Q

examples of hydrophobic signalling molecules

A

steroid hormones such as estrogen and testosterone

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13
Q

where do steroid hormones bind

A

they bind to specific receptors in the cytosol or the nucleus

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14
Q

what does the binding of steroid hormones form

A

hormone receptor complex

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15
Q

how does the hormone receptor complex work

A

The hormone-receptor complex moves to the nucleus where it binds to specific sites on DNA and affects gene expression .

The hormone-receptor complex binds to specific DNA sequences called hormone response elements (HRE’s)

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16
Q

what does the binding of the complex to HRE’s influence

A

influences the rate of transcription, with each steroid hormone affecting the gene expression of many different genes .

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17
Q

hydrophilic

A

A molecule that is attracted to water molecules and tends to be dissolved by water. Also known as polar molecules.

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18
Q

hydrophilic signalling molecules movement

A

they do not enter the cytosol and instead bind to transmembrane receptors

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19
Q

examples of hydrophilic extracellular signalling molecules

A

peptide hormones and neurotransmitters .

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20
Q

transmembrane receptors

A

Transmembrane receptors change conformation when the ligand binds to the extracellular face. The signal molecule does not enter the cell, but the signal is transduced across the plasma membrane.

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21
Q

transduction

A

Process by which a chemical or physical signal is transmitted through a cell by a series of molecular events resulting in a cellular response.

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22
Q

how to transmembrane receptors act as signal transducers

A

by converting the extracellular ligand-binding event into intracellular signals, which alters the behaviour of the cell.

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23
Q

what do transduced hydrophilic signals involve

A

G-protiens, cascades of phosphorylation by kinase enzymes

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24
Q

what do G-protiens do

A

relay signals from activated receptors to target proteins such as enzymes and ion channels .

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25
Q

what are activated receptors

A

receptors that have bound a signalling molecule

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26
Q

what do phosphorylation casacdes do

A

Phosphorylation cascades allow more than one intracellular signalling pathway to be activated. They involve a series of events with one kinase activating the next in the sequence and so on.

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27
Q

what do phosphorylation casacdes result in

A

Phosphorylation cascades can result in the phosphorylation of many proteins as a result of the original signalling event.

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28
Q

what does the binding of insulin do

A

Binding of the peptide hormone insulin to its receptor results in an intracellular signalling cascade that triggers recruitment of GLUT4 glucose transporter proteins to the cell membrane of fat and muscle cells.

29
Q

step 1 of insulin binding

A

Binding of insulin to its receptor causes a conformational change that triggers phosphorylation of the receptor.

30
Q

step 2 of insulin binding

A

This starts a phosphorylation cascade inside the cell

31
Q

step 3 of insulin binding

A

This phosphorylation eventually leads to GLUT4-containing vesicles being transported to the cell membrane.

32
Q

what is diabetes mellitus

A

caused by failure to produce insulin (type 1 ) or loss of receptor function (type 2 ).
Type 2 is generally associated with obesity.

33
Q

what does exercise trigger

A

triggers recruitment of GLUT4, so can improve uptake of glucose to fat and muscle cells in subjects with type 2 diabetes.

34
Q

what is a nerve impulse

A

a signal transmitted along a nerve fibre

35
Q

what is the resting membrane

A

state where there is no net flow of ions across the membranes

36
Q

what does the transmission of a nerve impulse require

A

requires change in the membrane potential of the neurons plasma membrane

37
Q

what is the action potential

A

wave of electrical excitation along a neurons plasma membrane

38
Q

what are neurotransmitters

A

chemicals that transmit a signal across a synapse

39
Q

what do neurotransmitters do

A

initiate a response by binding to their receptors at the synapse

40
Q

what type of receptors are neurotransmitter receptors

A

ligand gated ion channels

41
Q

what is depolarisation

A

a sudden change in membrane potential, usually from a relatively negative to positive internal charge

42
Q

what is depolarisation the result of

A

the entry of positive ions which triggers the opening of voltage gated sodium channels and causes further depolarisation

43
Q

how does the restoration of the membrane potential occur

A

the inactivation of the sodium channels and the opening of potassium channels

44
Q

what does the binding of a neurotransmitter do

A

triggers the opening of ligand-gated ion channels at the synapse

45
Q

how do sodium ions enter the cell

A

down a concentration gradient

46
Q

what do sodium ions lead to

A

rapid and large change in membrane potential

47
Q

action potential graph step 1

A

an external stimulus starts a rapid change in the voltage or action potential, this must reach above the threshold to start depolarisation

48
Q

action potential graph step 2

A

depolarisation is caused by a rapid rise in membrane potential by opening sodium channels in the membrane resulting in a large influx of sodium ions

49
Q

action potential graph step 3

A

repolarisation results from rapid sodium channel inactivation leading to a large influx of potassium ions from activated protien channels

50
Q

action potential graph step 4

A

hyperpolarisation is a lowered membrane potential caused by the effect of the loss of pottasium ions and the closing of pottasium channels

51
Q

action potential graph step 5

A

resting state is when membrane potential returns to resting voltage that it was before stimulus occurred

52
Q

what does depolarisation of a patch of membranes do

A

causes neighbouring regions of membranes to depolarise and go through same cycle as adjacent voltage gated sodium channels are opened

53
Q

what happens when action potential reaches the end of the neuron

A

causes vesicles containing neurotransmitters to fuse with membrane which releases neurotransmitters to stimulate a response to a connecting cell

54
Q

what does restoration of the resting membrane potential allow

A

inactive voltage gated sodium channels to return to original conformation that allows them to open again in response to depolarisation of the membrane

55
Q

what is reestablished by the sodium pottasium pump

A

ion concentration gradient

56
Q

how is ion concentration gradient re-established

A

by the sodium pottasium pump which actively transports excess ions in and out of the cell

57
Q

what follows repolarisation

A

the sodium and pottasium ion concentration gradients are reduced. the sodium pottasium pump restores the sodium and pottasium ions back to resting potential levels

58
Q

what is the retina

A

the area in the eye that detects light and contains 2 photoreceptor cells

59
Q

what are the two photoreceptors cells in the retina

A

rods and cones

60
Q

what are rods

A

function in dim light but do not allow colour perception

61
Q

what are cones

A

responsible for colour vision, need bright light to function

62
Q

what is combined to make the photoreceptors of the eye

A

retinal and opsin

63
Q

what is the retinal-opsin complex called

A

rhodopsin

64
Q

initiation of a nerve impulse in response to a stimulus (1)

A

rhodopsin absorbs a photon of light and changes conformation and becomes photoexcited rhodopsin

65
Q

what amplifies the signal from photoexcited rhodopsin (2)

A

a cascade of protiens

66
Q

initiation of a nerve impulse in response to a stimulus (3)

A

the photoexcited rhosopin activates G-protiens called transducin which activates enzyme PDE.
a single photoexcited molecule activates hundreds of transducin, each molecule then activates 1 PDE. PDE then catalyses the hydrolysis of cyclic GMP

67
Q

initiation of a nerve impulse in response to stimulus (4)

A

each PDE molecule breaks down thousands of cGMP per second.
this affects the function of ion channels in membrane of rod cells
results in the closure of ion channels which trigger nerve umpulses across the retina

68
Q

what allows opsin to function at low lights

A

a higher amplification allows opsin to function at lower light intensities

69
Q

what do different forms of opsin do in cone cells

A

give different photoreceptor protiens, each with maximal sensitivy to different wavelegnths of light such as red, blue , green and UV

advanced biology (6 decks)

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