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Molecular Biology of the Cell > Cell Signalling > Flashcards

Flashcards in Cell Signalling Deck (27)
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1
Q

What are examples of Endocrine Communication?

A

( Hormone travels within blood to act on distant target cell )

Insulin produced in pancreas acting on liver, muscle, adipose tissue

Adrenaline produced in Adrenal glands acting on trachea

2
Q

What are examples of Paracrine Communication?

A

( Hormone acts on an adjacent cell )

Nitric oxide produced by endothelial cells in blood vessels

Osteoclast activating factors produced by adjacent osteoblasts

3
Q

How does Insulin have both endocrine and paracrine effects?

A

Endocrine : Effects on liver

Paracrine : Secreted from beta cells and inhibits release of glucagon from adjacent alpha cells

4
Q

What is an example of signalling between proteins attached to membranes?

A

Blood borne viruses are detected by antigens on APCs

They then digest pathogen to express a MHC with class II molecules on surface

T lymphocytes engage through their own TCR interaction

5
Q

What detects HIV GP120 glycoproteins?

A

CD4 receptors on T lymphocytes ( Membrane attached protein signalling )

6
Q

What is Autocrine signalling? What are some examples of it?

A

Signalling molecule acts on the same cell.

Acetylcholine on presynaptic M2- muscaranic receptors

Activated T cell releases IL-2 and expresses an IL-2 receptor

7
Q

During Neurotransmission, when is cell signalling used?

A

Propagration of action potential by depolarisation and repolarisation

NT released from vesicles

Activation of post synaptic receptors

8
Q

How do Ionotropic receptors work?

A

Ligand binds to receptor protein

Channel protein changes shape = pore

Ions move along gradient

9
Q

What is the structure of a G-coupled receptor?

A

The channel protein crosses cell membrane 7 times

Linked to intracellular G protein complex :
alpha subunit ( are separated into 3 categories )
beta-gamma subunit
GDP molecule

10
Q

How do Enzyme linked receptors work?

A

Ligand binding causes receptors to cluster

Clustering activates enzyme activity within cytoplasmic domain

Enzymes phosphorylate receptor

This causes signalling proteins to bind to cytoplasmic domain

Signalling recruits further signalling

11
Q

What are Intracellular receptors?

A

A membrane permeable ligand binds to receptors inside cells

12
Q

What type of receptor does the ligand ACh use?

A

Ionotropic receptor

Nicotinic Acetylcholine
In skeletal muscles
Causes muscle contraction

13
Q

What receptors are used for
GABA
Glutamate
5-HT

A

( Ionotropic )
GABA(A) - inhibition of neuronal activity
NMDA - synaptic plasticity and memory formation
5-HT(3) - anxiety, emesis

14
Q

Which three categories are G-alpha subunits separated in and what are their roles?

A

G-alpha q/11 - ( 2nd messenger) Activates PLC ( effect 1) PIP(2) hydrolysed into IP(3) and DAG ( effect 2 ) Ip(3) promoted Ca2+ release from intracellular stores . DAG activates non-selective ion channels

G-alpha s - ( 2nd messenger ) Activates AC ( effect 1 ) Converts ATP to cAMP ( effect 2 ) Activates PKA

G-alpha 1/o - ( 2nd messenger ) Inhibits AC ( effect 1 ) Reduces cAMP formation ( effect 2 ) inhibits PKA

15
Q

How are 7-TM receptor and heterotrimeric G-protein made active?

A

They are inactive

Ligand binding changes shape of receptor

Unassociated G-protein binds to receptor

Bound GDP molecule phosphorylated to GTP

G protein dissociated into an alpha and beta-gamma subunit

The subunits bind to their target proteins

16
Q

How are the 7-TM receptor and heterotrimeric G-protein made inactive?

A

GTPase in cell acts on alpha subunit which desphorylates the GTP into GDP

beta-gamma subunit also leaves target protein and both join to make the inactive G protein

  • If 7-TM receptor is active because ligand remains bound, further heterotrimeric G proteins can be activated
17
Q

What do G-alpha and G-beta-gamma subunits act as?

A

Secondary Messengers

18
Q

Give Examples of G protein-coupled receptors with their respective ligands and physiological effects? (4)

A

Angiotensin II –> AT-1 receptor. G-alpha q subunit :
Vasoconstriction, increased blood pressure

Acetylcholine –> M3 muscarinic receptor. G-alpha q subunit : Bronchoconstriction, decreased air flow

NE/ Ad –> Beta1 adrenergic receptor. G-alpha s subunit :
Increased heart rate, increased force on contraction

Dopamine –> D1 receptor. G-alpha s subunit :
Increased neuronal growth

19
Q

Which Enzyme linked receptors do:

Insulin
ANP/BNP
TGF beta

Bind to?

A

Insulin CD220 receptor. Enzyme : Tyrosine kinase

NPR1 receptor. Enzyme : GC ( vasodilation, reduces bp )

TGF beta R1. Enzyme : Ser/Thr Kinase ( apoptosis )

20
Q

What do Steroid Hormones target?

A

They are hydrophobic so go directly to intracellular receptors.

Mostly transcription factors

21
Q

What are Type I intracellular receptors?

A

In cytosol

Receptors are bound to chaperone molecules

When hormone binds the chaperone molecule dissociates

The hormone-receptor complex joins another hormone-receptor complex to form a homodimer

Homodimer goes to nucleus to bind to DNA ( acts as transcription factor )

22
Q

What are Type II intracellular receptors?

A

In nucleus ( often already bound to DNA )

Hormone ligand binding leads to directly transcriptional regulation as Hormone-complex is activated straight away

23
Q

How does the hormone Cortisol cause stress, immunosuppression and gluconeogenesis?

A

Binds to GC-R in cytosol. ( Type I intracellular receptor )

Regulates transcription

24
Q

How does Estradiol result in female sexual development?

A

Binds to Cytosolic ER-alpha receptor. ( Type I intracellular receptor )

Regulates transcription

25
Q

How does Thyroxine cause increased metabolism and greater physical development?

A

Binds to nuclear TR-alpha receptor. ( Type II intracellular receptor )

Regulates transcription

26
Q

Which condition is due to a disorder of membrane-attached proteins

A

lupus
multiple sclerosis
Myasthenia gravis
rhuematoid arthiritis ?

(which one?)

27
Q

Which receptor class: ErbB receptor

A

Enzyme linked ( I think )