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Advanced higher biology > 1.4 communication and signalling > Flashcards

1.4 communication and signalling Flashcards

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1
Q

Extracellular signalling molecules definition

A

Molecules that a multicellular organism uses to send messages between different cells, which are produced outside the cell.

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2
Q

Types of extracellular signalling molecules

A

Peptide hormones
Steroid hormones
Neurotransmitter

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3
Q

Nervous communication definition

A

The transport of electrical signals across neurones.

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4
Q

Hormonal communication definition

A

The transport of extracellular signalling molecules around the body.

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5
Q

Nervous communication nature of signal

A

Electrical impulses and neurotransmitter

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6
Q

Nervous communication transmission of signal

A

Across a neurone

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7
Q

Nervous communication target cell

A

Any cell with a connection to neurones

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8
Q

Nervous communication time for response to occur

A

Fast

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9
Q

Nervous communication duration for response

A

Shorter

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10
Q

Nervous communication extent of response

A

Localised
(specific)

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11
Q

Hormonal communication nature of signal

A

Extracellular signalling molecules

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12
Q

Transmission of hormonal communication

A

Through blood stream

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13
Q

Hormonal communication target cells

A

Any cell in body

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14
Q

Hormonal cells time for response to occur

A

Slower

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15
Q

Duration of hormonal communication

A

Longer

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16
Q

Extent of hormonal communication response

A

Widespread

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17
Q

Hydrophobic extracellular signalling molecules

A

Steroid hormones

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18
Q

Hydrophilic extracellular signalling molecules

A

Peptide hormones and neurotransmitters.

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19
Q

Receptor molecules definition

A

A molecule with a specific binding site for an extracellular signalling molecule, which changes conformation upon binding with the ligand.

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20
Q

How do receptors on the outside of cells work

A

A conformational change occurs which initiated a response inside the cell.

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21
Q

Characteristics of receptors

A

Different cell types produce different signalling molecules
Different receptors will bind to different signalling molecules
Different types of cell tissue with same receptor and signal molecule can trigger different metabolic pathways

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22
Q

Tissue specific response

A

Where a different cell tissue with the same signalling molecule and receptor will trigger a different intracellular pathway.

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23
Q

Steroid/ hydrophobic signalling molecule process

A

Leave endocrine gland and travel straight to the cell through bloodstream.
Travel through the plasma membrane.
Bind with receptor inside the cell forming a hormone receptor complex.
The transcription factor will bind with DNA in nucleus
This will then stimulate or inhibit the transcription of DNA.
This will increase or decrease the rate of specific protein production.

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24
Q

Hormone receptor complex

A

Where a hormone and a receptor bind together

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25
Q

Hormone response elements

A

Sites on DNA which hormone transcription factors will bind with which will alter the rate of transcription.

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26
Q

Transcription factors

A

Hormone receptor complexes which bind to DNA at transcription elements.

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26
Q

Steroid hormone examples

A

Testosterone and oestrogen

27
Q

Where do steroid hormones bind to receptors

A

Cytosol or nucleus

28
Q

Where do hydrophilic and peptide hormones bind to receptors

A

On the outside of the plasma membrane since they cannot travel through the plasma membrane

29
Q

Hydrophilic peptide hormones process of communication

A

Peptide hormone will be released from endocrine gland and travel through blood stream to cell.
Peptide hormone binds to the receptor on outside of the plasma membrane
This will activate a G protein inside the cell converting GDP to GTP.
GTP will phosphorylate the protein and activate the protein.
The activated protein will start a phosphorylation cascade.

30
Q

Transduction

A

Where a hydrophilic signalling molecule binds to a receptor and causes a change in the cell behaviour.

31
Q

Examples of hydrophilic signalling molecules

A

Neurotransmitters and peptide hormones

32
Q

Phosphorylation cascades

A

Where a protein activates another protein by phosphorylating the protein,

33
Q

What type of proteins are G proteins

A

Kinases - since they add a phosphate to another molecule activating it.

34
Q

Blood glucose level hormones

A

Insulin and glucagon

35
Q

Blood sugar level decrease process

A

Blood glucose level is detected
Insulin produced by cells in pancreas.
Insulin binds as a ligand to the receptor molecules outside the plasma membrane.
This activates a G protein inside the cell.
This G protein phosphorylates GDP to GTP.
This GTP will then phosphorylate a protein causing a phosphorylation cascade.
This will recruit Glut 4 vesicles
Glut 4 vesicles will bind to the plasma membrane releasing Glut 4
Glut 4 will then transport glucose into the cell by facilitated diffusion.

36
Q

Glut 4

A

A glucose transporter protein which transports glucose into the cell by facilitated diffusion.

37
Q

Type 1 diabetes

A

Caused by failure to produce insulin

38
Q

Type 2 diabetes

A

Caused by loss of insulin receptor sensitivity

39
Q

What is type 2 diabetes caused by

A

Associated with obesity

40
Q

Treatment for type 2 diabetes

A

Exercise since Glut 4 recruitment occurs in another metabolic pathway.

41
Q

Process of a neurone firing

A

Neurotransmitters will travel across the synapse and bind to ligand gated ion channels on the dendrite’s plasma membrane. These ligand gated ion channels will open and allow for ions to undergo facilitated diffusion into the neurone. If many ligand gated ion channels open at once then the membrane potential will change from -70mv to -55mv, allowing for the threshold to be reached, and this will allow voltage gated Na+ channels to open and allow sodium ions to undergo facilitated diffusion into the cell. This will depolarise the cell, increasing the membrane potential to +40mv. When this occurs the voltage gated sodium channels will close and voltage gated potassium ion channels will open, allowing potassium to diffuse out of the cell (facilitated diffusion). This will allow for the cell to repolarise, which will decrease the cell membrane potential back down to -70mv and potassium channels will close, however the potassium channels will close too slowly and more potassium ions will leave the cell. Causing a hyper-polarisation. The sodium potassium pump will then activate and restore the membrane potential back to -70mv. The sodium potassium pump works by 3 sodium ions binding to an inwards facing high affinity binding site. ATP will then break down into ADP and Pi, which will then phosphorylate the sodium potassium pump, this will cause a conformational change releasing sodium out of the cell. Potassium will then bind to the new high affinity outwards facing binding site on the outside of the plasma membrane. The sodium potassium pump will dephosphorylate, which will allow for a conformational change to occur releasing 2 potassium ions into the cell and reverting the pump back to its original inwards confirmation. The process is then repeated. This depolarisation, depolarisation and hyper-polarisation will cause an electrical signal to travel down the axon to the presynaptic terminal.

42
Q

Dendrite

A

The location on a neurone where the neurotransmitters bind to their ligand gated ion channels

43
Q

Axon

A

The location in a neurone where an action potential will travel down.

44
Q

Presynaptic terminal

A

The location in a neurone where the neurotramitters are released to travel across the synapse

45
Q

Depolarisation

A

Where sodium ions will enter a cell through voltage gated ion channels increasing the membrane potential form -55 to +40

46
Q

Repolarisation

A

Where potassium ions will travel out of a cell through voltage gated ion channels decreasing the membrane potential from +40 to -70

47
Q

Hyperpolarisation

A

Where voltage gated ion channels in potassium will close to slowly - resulting in the membrane potential decreasing below -70 mv

48
Q

How are ion gradients re established

A

Sodium potassium pump

49
Q

Action potential

A

Where a neurone depolarises, repolarises and then hyperpolarises causing an electrical signal down the axon .

50
Q

How does an action potential begin

A

With ions increasing the membrane potential to -55 mv

51
Q

Types of ions in neurones

A

Inhibitory and excitatory ions

52
Q

Inhibitory ions

A

Ions which decrease the membrane potential of a neurone away from the depolarisation threshold

53
Q

Excitatory ions

A

Ions which increase the membrane potential towards the depolarisation threshold.

54
Q

Area of the eye which detects light

A

Retina

55
Q

Types of cells in the retina (photoreceptor cells)

A

Cone cells and rod cells

56
Q

Rod cells function

A

Detect dim light without colour perception

57
Q

Cone cells

A

Detect high intensity light with colour perception

58
Q

Rhodopsin

A

A complex formed from a retinal prosthetic group and an opsin molecule

59
Q

Different types of opsin

A

Cone cells have different types of opsin, rod cells have one type of opsin

60
Q

Process of nervous impulse behind eye

A

Retinal group absorbs light and conformational change from rhodopsin to photoexcited rhodopsin occurs.
This activates the G protein transducin
This excites the enzyme PDE
PDE converts cGMP to GMP
cGMP concentration decrease is detected by sodium ion channels closing sodium ions channels to close.
This will cause a hyperpolarisation as the membrane potential decreases.
This will allow the neurones behind the eye to fire and send electrical impulses to other neurones.

61
Q
A
62
Q

Adaptation of cone cells for high light intensity

A

Have different forms of opsin to absorb different wavelengths of light at maximum intensity

63
Q

Quantities for eye process

A

photo- excited rhodopsin will activate hundreds of G proteins.
1 G protein will excite 1 PDE
PDE will break down thousands of cGMP each second.

64
Q
A

Advanced higher biology (11 decks)

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