Cell to Cell communication

Question 1

What is needed to convey info. from a signalling cell to a target cell? (3)

Answer 1

• signalling molecules
• ligands
• transmitters

Question 2

Most receptors are _______ . Some receptors are __________

Answer 2

• transmembrane proteins

- intracellular

Question 3

State what is meant by “all parts of cell-to-cell communication is dynamic” (3)

Answer 3

• amount of cell signalling molecule that is produced
• the way that the cell signalling molecules are transported
• the expression of receptors

Question 4

State the 2 types of effects of signalling molecules

Answer 4

• local effect

- distant effect

Question 5

State 3 types of signalling molecules w/ local effects

Answer 5

• contact-dependent
• paracrine signalling
• autocrine signalling

Question 6

Outline these 3 types of signalling molecules (local effects)

Answer 6

contact-dependent

• the signalling cell is physically adjacent to the target cell
• a membrane bound signal can be expressed, generated, & transferred to the target cell
• there can be some kind of pore in b/n these two cells as well

paracrine signalling

• via soluble messengers
• may tell local cells that smth is going wrong & recruit more cells

autocrine signalling
- the signalling cell is also the target cell

Question 7

State 2 types of signalling molecules w/ distant effects

Answer 7

• endocrine signalling

- synaptic signalling

Question 8

Outline these 2 types of signalling molecules (distant effects)

Answer 8

endocrine signalling
- one kind of tissue type secretes a signalling molecule which is typically carried in the blood

synaptic signalling
- the signal is transmitted down the neurone & passed to the target cell

Question 9

State the function of neuronal communication (4)

Answer 9

• acquire info.
• transmit
• integrate
• bring about a response to the stimulus

Question 10

State how neuronal communication initially acquires info. (2)

Answer 10

• sensory input via external environ. (e.g temp, touch, sound)
• internal environ. (e.g blood pH, taste, pressure)

Question 11

State how info. is transmitted

Answer 11

via electrical signal, action potentials

Question 12

State where signal transmission b/n nerves / b/n nerves & effectors occur

Answer 12

synapse

Question 13

State what synaptic transmission is mediated by

Answer 13

neurotransmitters

Question 14

List advantages of neuronal communication (2)

Answer 14

• fast

- selective targets

Question 15

List disadvantages of neuronal communication

Answer 15

energetically expensive

Question 16

State where transmitters are released from in endocrine communication

Answer 16

from specialised cells forming endocrine glands

Question 17

State how transmitters are distributed in endocrine communication

Answer 17

transmitters ener the blood stream & are distributed systematically

Question 18

State how transmitters achieve specificity

Answer 18

by activating target cells which express the cognate receptor

Question 19

State what the duration of signal depends on

Answer 19

the half life of the transmitter

Question 20

State 4 possible cellular responses

Answer 20

• depolarization (neurons)
• depolarization & electro-mechanic coupling (muscle)
• depolarization & secretion (endocrine glands)
• transcriptional & translational effects (all cell types)

Question 21

State 2 types of hormone receptors & give an example

Answer 21

• intracellular (e.g. transcription factors)

- plasma membrane bound (e.g G protein coupled receptors)

Question 22

Explain the structure of hormone receptor type: plasma membrane (3)

Answer 22

• all membrane receptors have 3 domains (regions)
• N terminus is on extracellular domain
• C terminus is on intracellular domain

Question 23

State 3 major classes of cell surface receptors

Answer 23

ion channel linked receptor

• enzyme linked receptor
• G-protein coupled receptor (GPCRs)

Question 24

Describe the first major class of cell surface receptors (3)

Answer 24

ion channel linked receptor

• a.k.a ligand gated channels
• when ligands bind to the receptor, the ion channel portion of the receptor opens
• allows ions to pass across cell membrane

Question 25

Describe the second major class of cell surface receptors (2)

Answer 25

enzyme linked receptor

• transmembrane receptor
• the binding of an extracellular ligand causes enzymatic activity on the intracellular side (activates an intracellular enzyme)

Question 26

Describe the third major class of cell surface receptors (2)

Answer 26

GPCRs

• a.k.a 7-pass-transmembrane domain receptors (7TM receptors)
• only found in eukaryotes

Question 27

Explain how GPCRs function (3)

Answer 27

1. binds extracellular substances & transmits signals from these substances to a G protein (intracellular)
2. trimeric G-proteins relay the signal
3. coupling the receptor to its target (enzyme/ion channel) generates second messengers

Question 28

Explain how the secondary messenger, cAMP is synthesized via GPCRs function (3)

Answer 28

1. free active stimulatory G-proteins interacts w/ adenylyl cyclase (enzyme) at membrane
2. adenylyl cyclase generates cAMP from ATP
3. produces rapid rise in the conc. of cAMP

Question 29

State the function of cAMP (2)

Answer 29

1. activates the regulatory serine-threonin protein kinase (PKA) (cAMP-dependent protein kinase)
2. phosphorylates specific target proteins to produce specific effect