L3 Communication Between Cells

Question 1

Types of intercellular communication

Answer 1

• Autocrine: cell signals to itself
• Paracrine: cell signals to neighbouring cell
• Signalling via proteins attached to cell surface
• Synapic transmission: neurons
• Endocrine- endocrine cells release hormones to distant cells

Question 2

Receptor def and function

Answer 2

Specialised protein
Receptor RECOGNISES signalling molecules
Binds to ligand
Trigger cellular responses-ACTION
When ligand binds the receptor changes shape
Can change function of cell

Question 3

Activation of receptor can lead to

Answer 3

Means when Ligand and receptor attach :

• Changes in cell growth and division (mitosis)
• Change cell membrane permeability

Question 4

Different classes of receptors

Answer 4

Intercellular - in nucleus or free floating in cytoplasm
OR
On cell surface

Note: receptors in cytoplasm do nothing

Question 5

If ligand and intracellular receptor bind give an ex of a new function protein might gain as result

Answer 5

Permeability to cell membrane might increase

Question 6

Intracellular receptors for signalling molecules which CAN pass through cell membrane

Answer 6

• Receptor & ligand bind
• Attach to DNA- results in activation of specific genes
• Results in activation of proteins
• These proteins can change cell function
• Note: only for LIGANds that can pass cell membrane

Question 7

Eg of intercellular receptors

Answer 7

Steroid and thyroid hormone receptors

Question 8

Where are receptors located for Ligand that can’t pass cell membrane

Answer 8

On cell surface

Question 9

Second Messengers - what are they ?

When do receptors usually characterise SM

Answer 9

• Intracellular substance that can mediate cell activity by release or relaying of a signal of an extra cellular molecule bound to cell surface
• released by cell to cause a physiological change
• Receptors on cell membrane
  E.g. ACh and adrenalin (hormone)

Question 10

Cell charge for all? Ions:

Answer 10

Outside is +

Inside is -

Question 11

Receptors found on cell membrane- list 3

Answer 11

• receptors which are ION CHANNELS
• receptors which are ENZYMES or bound to enzymes (protein KINASES cause phosphorylation)
• receptors which act as G-PROTEINS

Question 12

Receptors which act as G protein
Activation process

Video NB

Answer 12

process from video

• Ligand binds to receptor that has alpha beta and gama subunits attached
• alpha has ADP attached also
• once Ligand binds sub units move away
• ATP now binds to alpha
• alpha moves away from beta and gama
• if Ligand is removed, alpha phosphorylates ; ADP binds back
• subunits return together to the receptor

Lecture notes

• They usually bind to other proteins changing their functions by binding to them (allosteric)
• May lead to activation of some enzymes to for e.g. Modulate ion channels - change MP.

E.g. Of receptor - ADRENALIN are receptor

Question 14

Intracellular receptors bind to DNA and thus have a direct effect on : GENE EXPRESSION

Answer 14

• Have a direct effect in gene expression bcos they bind to - DNA
• Ligand & receptor
• DNA
• Genes
• Altered function

Question 15

Receptors which act as G protein
Activation process

Video NB

Answer 15

-When activated, receptors make G-proteins separate into 2 subunits: alpha
Beta and gama

• They usually bind to other proteins changing their functions by binding to them (allosteric)
• May lead to activation of some enzymes to for e.g. Modulate ion channels - change MP.

E.g. Of receptor - ADRENALIN are receptor

Question 16

Note what receptors use second and third intermediates to amplify initial signal

Answer 16

Receptors - enzymes and GCPR’s

Question 17

Receptor that are ion channels- how it works

Answer 17

Ion Channels: form pores in membrane that allow ions to pass through

• occurs for nerve and muscle cells- excitable cells which have RMP & can generate AP
• eg nACh Receptors
• Open if ACh binds
• Thus Na goes DOWN its conc gradient??? and goes INTO cell
• Depolarises membrane

E.g. ACh receptors in skeletal muscle