1.4 communication and signalling

Question 1

Extracellular signalling molecules definition

Answer 1

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

Question 2

Types of extracellular signalling molecules

Answer 2

Peptide hormones
Steroid hormones
Neurotransmitter

Question 3

Nervous communication definition

Answer 3

The transport of electrical signals across neurones.

Question 4

Hormonal communication definition

Answer 4

The transport of extracellular signalling molecules around the body.

Question 5

Nervous communication nature of signal

Answer 5

Electrical impulses and neurotransmitter

Question 6

Nervous communication transmission of signal

Answer 6

Across a neurone

Question 7

Nervous communication target cell

Answer 7

Any cell with a connection to neurones

Question 8

Nervous communication time for response to occur

Answer 8

Fast

Question 9

Nervous communication duration for response

Answer 9

Shorter

Question 10

Nervous communication extent of response

Answer 10

Localised
(specific)

Question 11

Hormonal communication nature of signal

Answer 11

Extracellular signalling molecules

Question 12

Transmission of hormonal communication

Answer 12

Through blood stream

Question 13

Hormonal communication target cells

Answer 13

Any cell in body

Question 14

Hormonal cells time for response to occur

Answer 14

Slower

Question 15

Duration of hormonal communication

Answer 15

Longer

Question 16

Extent of hormonal communication response

Answer 16

Widespread

Question 17

Hydrophobic extracellular signalling molecules

Answer 17

Steroid hormones

Question 18

Hydrophilic extracellular signalling molecules

Answer 18

Peptide hormones and neurotransmitters.

Question 19

Receptor molecules definition

Answer 19

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

Question 20

How do receptors on the outside of cells work

Answer 20

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

Question 21

Characteristics of receptors

Answer 21

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

Question 22

Tissue specific response

Answer 22

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

Question 23

Steroid/ hydrophobic signalling molecule process

Answer 23

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.

Question 24

Hormone receptor complex

Answer 24

Where a hormone and a receptor bind together

Question 25

Hormone response elements

Answer 25

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

Question 26

Transcription factors

Answer 26

Hormone receptor complexes which bind to DNA at transcription elements.

Question 26

Steroid hormone examples

Answer 26

Testosterone and oestrogen

Question 27

Where do steroid hormones bind to receptors

Answer 27

Cytosol or nucleus

Question 28

Where do hydrophilic and peptide hormones bind to receptors

Answer 28

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

Question 29

Hydrophilic peptide hormones process of communication

Answer 29

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.

Question 30

Transduction

Answer 30

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

Question 31

Examples of hydrophilic signalling molecules

Answer 31

Neurotransmitters and peptide hormones

Question 32

Phosphorylation cascades

Answer 32

Where a protein activates another protein by phosphorylating the protein,

Question 33

What type of proteins are G proteins

Answer 33

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

Question 34

Blood glucose level hormones

Answer 34

Insulin and glucagon

Question 35

Blood sugar level decrease process

Answer 35

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.

Question 36

Glut 4

Answer 36

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

Question 37

Type 1 diabetes

Answer 37

Caused by failure to produce insulin

Question 38

Type 2 diabetes

Answer 38

Caused by loss of insulin receptor sensitivity

Question 39

What is type 2 diabetes caused by

Answer 39

Associated with obesity

Question 40

Treatment for type 2 diabetes

Answer 40

Exercise since Glut 4 recruitment occurs in another metabolic pathway.

Question 41

Process of a neurone firing

Answer 41

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.

Question 42

Dendrite

Answer 42

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

Question 43

Axon

Answer 43

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

Question 44

Presynaptic terminal

Answer 44

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

Question 45

Depolarisation

Answer 45

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

Question 46

Repolarisation

Answer 46

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

Question 47

Hyperpolarisation

Answer 47

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

Question 48

How are ion gradients re established

Answer 48

Sodium potassium pump

Question 49

Action potential

Answer 49

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

Question 50

How does an action potential begin

Answer 50

With ions increasing the membrane potential to -55 mv

Question 51

Types of ions in neurones

Answer 51

Inhibitory and excitatory ions

Question 52

Inhibitory ions

Answer 52

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

Question 53

Excitatory ions

Answer 53

Ions which increase the membrane potential towards the depolarisation threshold.

Question 54

Area of the eye which detects light

Answer 54

Retina

Question 55

Types of cells in the retina (photoreceptor cells)

Answer 55

Cone cells and rod cells

Question 56

Rod cells function

Answer 56

Detect dim light without colour perception

Question 57

Cone cells

Answer 57

Detect high intensity light with colour perception

Question 58

Rhodopsin

Answer 58

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

Question 59

Different types of opsin

Answer 59

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

Question 60

Process of nervous impulse behind eye

Answer 60

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.

Question 62

Adaptation of cone cells for high light intensity

Answer 62

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

Question 63

Quantities for eye process

Answer 63

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.