PA20292- Amanda Mackenzie lectures Flashcards Preview

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Flashcards in PA20292- Amanda Mackenzie lectures Deck (122)
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What is direct cell-cell signalling?

Receptor on surface of one cell detects ligand on surface of other cell. Cells physically connect.

1

What is endocrine cell signalling?

Uses hormone transported in blood to send messages throughout the body.

2

What is autocrine cell signalling?

Cell signals to ITSELF. the molecule released acts back on itself.

3

What is paracrine cell signalling?

Cell signals to a nearby neighbour by release of a molecule.

4

What is the pathway of cell signalling (4 stages)?

Signal, reception, transduction, response.

5

Basic definition of a receptor?

Receptors are proteins that bind to specific ligands/agonists.
Receptors have an affinity for the ligand.

6

Difference between competitive and non competitive inhibitors?

Non competitive; binds somewhere else on receptor causing a conformational change so that the ligand can no longer bind.
Competitive: competes for same binding site as ligand, stops the response.

7

Where are nuclear receptors located?

Inside the cell. They are intracellular. Not in nucleus but in cytoplasm.

8

3 domains of the nuclear receptor superfamily?

Ligand binding
DNA binding
Transcription activation (gene transcription)

9

What must drugs be in order to bind to nuclear receptors?

LIPID SOLUBLE. they have to cross the cell membrane to reach the nuclear receptor. ( lipophillic)

10

Another name for ligand gated ion channels?

Ionotropic receptors.

11

Where are ligand gated ion channel receptors located?

The membrane of a cell. Occur in all cell types.

12

2 other names for g protein coupled receptors?

7transmembrane, metabotrophic

13

What do g protein coupled receptors consist of?

Seven transmembrane alpha helices
Intracelluar loop (the largest loop interacts with the g protein)
3 subunits: alpha beta gamma. Forms a-B-y trimer.
Binding domain for agonist on the receptor molecule.
Binding site for GDP/ GTP on the a subunit.

14

What does a kinase enzyme do?

It will phosphorylate it's substrate.
Or phosphorylase itself (auto phosphorylation)
ATP is the source of phosphate
Phosphates can be added to tyrosine threonine or serine amino acids.

15

4 examples of ligands for ligand gated ion channels?

NDMA, Glycine, GABA, Ach

16

What do mechanically gated ion channels do?

Open in response to mechanical movement of adjacent structures, respond to stretch and temperature.

17

How do you measure the activity of an ion channel?

Use patch clamp recordings

18

What are patch clamp recordings?

A patch of membrane with a single ion channel on it is monitored.
The current of this ion channel is recorded using an electrode.
The flickering (opening and closing) of an ion channel is detected on the recording.
Allows the very small current flowing through an ion channel to be measured directly.

19

What is the nicotinic acetyl choline receptor directly coupled to?

It is a ligand gated ion channel directly coupled to a cation selective ion channel

20

How many subunits is the acetyl choline receptor made up of?

5
a,a,B,δ,y

21

How is the acetyl choline receptor structure determined?

By crystallography experiments

22

What is a heteromeric ion channel?
What is a homomeric ion channel?

Heteromeric channels are composed of several different subunits
Homomeric channels are composed of the same subunits

23

Is the ACh receptor heteromeric or homomeric?

Heteromeric, consists of different subunits

24

Where a outs does ACh bind on the receptor?

ACh binding sites are on the extra cellular portion of the receptor at the interface between the alpha and adjoining subunits.

25

What happens when Ach binds to the ACh receptor?

The kinked alpha helices that act as a gate swing out the way and open the channel pore.
Opening the pore allows NA+ and K+ to diffuse down the channel depolarising the membrane.

26

The permeability of ____ increases when Ach binds to the Ach receptor?

Na+ and K+ . This causes the membrane to depolarise carrying the action potential.

27

Difference between nicotinic and muscarinic Ach receptors

Nicotinic are ionotropic receptors, meaning that they allow ions to pass through them when they bind to acetylcholine. Therefore, these receptors help depolarize the cell in response to acetylcholine and are excitatory.

Muscarinic are metabotropic receptors (G-protein coupled receptors). They activate G-proteins in response to acetylcholine and these G-proteins can have different cellular responses depending on which G-proteins are activated.

28

What is the ultimate response of the Ach signal binding to ACh receptors?

Muscle contraction.
Opening of Na+ channel (reception) then Influx of Na+ and depolarisation of membrane (transduction) results in Ca2+ release which in turn results in muscle contraction as the ultimate response.

29

What is long QT syndrome? What channel tends to be effected by this?

hERG (Kv1.11) is a voltage gated potassium channel.
This channel mediates the repolarisation of the cardiac action potential in the heart and is essential in keeping a normal cardiac rhythm.
Mutations in this ion channel may inhibit it causing delayed repolarisation of the heart after a heart beat. This can lead to TDP, an irregular heartbeat. This results in the prolongation of the QT interval and can result in sudden death.

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