L01 Cell Communication

Question 1

Endocrine signalling

Answer 1

Hormone released directly into the bloodstream to reach target cell

Question 2

Paracrine signalling

Answer 2

• Targets neighbouring cells
• eg synaptic transmission

Question 3

Autocrine signalling

Answer 3

Targets site on same cell

Question 4

How are effects of first messengers mediated

Answer 4

By binding to specific receptors

Question 5

4 main types of receptors

Answer 5

• LG ion channels
• kinase linked receptors
• Gprotein coupled receptors
• nuclear receptors

Question 6

How do LG ion channels work as receptors

Answer 6

• Bring about effect by depolarisation/ hyper-polarisation of the membrane
• v fast
• e.g nicotinic acetylcholine receptor

Question 7

How do G coupled protein receptors work as receptors

Answer 7

• binding of the first messenger to the receptor activates a G protein- interacts with other proteins causing effects
• v fast
• e.g muscarine acetylcholine receptor

Question 8

How do Kinase linked receptors work?

Answer 8

• Binding of the first messenger stimulates kinase (phosphorylates) - phosphorylates proteins leading to effects
• fast
• e.g cytokine receptors

Question 9

What are nuclear receptors?

Answer 9

• First messenger passes through membrane and into nucleus where it binds to TF or genome = alters genetic activity
• slow
• e.g oestrogen receptor

Question 10

What is the antagonist and agonist for nicotinic receptors

Answer 10

Agonist = nicotine
Antagonist = curare

Question 11

Role of nicotinic Ach receptors

Answer 11

• Associated with ligand gated ion channel receptors
• in absence of Ach = closed
• Ach binds = causes channel gate to open due to hydrophobic interactions upon binding
• Allows ions to enter (changes membrane potential)= allows signals to be propagated in the second cell

Question 12

What type of receptor are muscarinic receptors

Answer 12

• associated with G coupled protein receptors

Question 13

What are the agonist and antagonist for muscarine receptors

Answer 13

Agonist - muscarine
Antagonist - alkaloids e.g atropine
- too much can cause salvation, bradycardia (slow heart rate)

Question 14

G protein coupled receptor mechanism

Answer 14

• mediate the effects of many hormones and neurotransmitters
• messenger (hormone) binds to a receptor resulting in a conformational change
• this interacts with G protein - conformational change- exchanges molecule of GDP for GTP on alpha subunit
• Cause G protein to disassociate from the receptor and subunits (alpha and beta) to separate - each mediating different effects:
  — Gas activates adenyl cyclase which converts ATP into cAMP - second messenger. Gai deactivates AC
  — B unit and GAq activate phopholipase C and various ion channels
• the alpha subunit dephosphorylates and the G proteins reassembles and reassociates with the receptor

Question 15

How do receptors work

Answer 15

• first messenger binds
• produces intracellular second messagers

Question 16

What is an agonist and antagonistic?

Answer 16

Agonist =A substance that produces the same effects as the neurotransmitter

Antagonist = substance that binds to receptor but interferes with or inhibits the action of another substance

Question 17

Overview of the Otto Loewi experiment

Answer 17

• put 2 dissected frog hearts in beakers with a bridge connected both so fluids could flow between
• recorded contractions of both hearts
• stimulates nerve in heart 1and saw heart 2 also stimulated = something released from heart 1

Question 18

Why do antagonist and agonist need to be similar in shape

Answer 18

• need to be structurally similar so they fit into the same active site of the receptor but other compounds of the molecule can be different