Cell signalling

Question 1

Why do cells need to communicate?

Answer 1

Process information - sensory stimuli
Self preservation - fight or flight - spinal reflexes for sympathetic nervous system
Voluntary movement
Homeostasis - thermoregulation/glucose homeostasis

Question 2

Hypoglycaemia is an example of?

Answer 2

Endocrine communication - leads to glycogen breakdown + gluconeogenesis
Glucagon secreted by a cells in pancreas ; glucagon travels out of pancreas in blood vessels and stimulates both processes within the liver

Question 3

Endocrine signalling

Answer 3

When a hormone travels via blood from organ to another organ

Question 4

Insulin

Answer 4

Another type of endocrine signalling ; acts on muscle/adipose tissue/liver

Question 5

Adrenaline

Answer 5

Acts on trachea - endocrine signalling

Question 6

Hyperglycaemia - mechanism of insulin can also be?

Answer 6

PARACRINE SIGNALLING - insulin secretion via b cells and acts on alpha cells next to it to inhibit glucagon secretion (as well as endocrine function in the liver)

Question 7

Paracrine signalling?

Answer 7

Hormone acts on adjacent cells

Question 8

Other examples of paracrine signalling

Answer 8

Nitric oxide produced by endothelial cellist blood vessels- vasodilation (reduces blood pressure)
Osteoblast activating factors produced by adjacent osteoblasts

Question 9

Osteoblast

Answer 9

Cell which secretes the substance of bone

Question 10

Signalling between membrane attached proteins

Answer 10

The pathogen is detected by an APC which digests the pathogen and expresses the MHC class II molecule on the surface ; circulating T-lymphocyte engages with MHC through TCR

Question 11

Membrane attached proteins

Answer 11

Plasma membrane proteins on adjacent cells interact

Question 12

Examples of membrane attached proteins

Answer 12

HIV gp120 glycoprotein with CD4 receptor on T lymphocytes
Bacterial cell wall components detection ; using receptors on heatopoietic cells

Question 13

Autocrine signalling with T cell

Answer 13

Activated TCR will initiate a cascade of reactions within T cell and that will express IL-2 receptor on surface
T cell secrete IL-2 molecules which can now bind to IL-2 receptors on the same cell and those on adjacent cells (paracrine)

Question 14

Examples of autocrine

Answer 14

Acetylcholine -> presynaptic M2 muscarinic receptors
Growth factors from tumour cells leading to mitogenesis

Question 15

Neurotransmission mechanism

Answer 15

Propagation of action potential by VGSCs ; NA+ influx leads to membrane depolarisation and there is then a K+ efflux
AP opens ca2+ channel at presynaptic terminal ; ca2+ influx causes acetylcholine exocytosis
NT binds to receptors on post synaptic neurone
Activation of post synaptic receptor

Question 16

Post synaptic cell

Answer 16

Can be muscle neurone whatever

Question 17

4 types of receptors

Answer 17

Ionotropic receptor - ligand binding causes ion permeable pore to open
G protein coupled receptor ; ligand binding activates intracellular G-protein
Enzyme linked receptor - ligand binding results in receptor clustering causing activation of internal enzymes
Intracellular receptor - membrane permeable ligand binds to receptor inside cell

Question 18

Iontropic receptors

Answer 18

Ligand binds to receptor protein and this changes conformation of channel protein ; pore now allows ions to move in and out of cell (respective to conc gradients)

Question 19

Ionotropic receptor example

Answer 19

Nicotinic Acetylcholine ; ligand is Ach ; located in the skeletal muscle and results in muscle conc

Question 20

GABA channels

Answer 20

Ion channels

Question 21

G-protein coupled receptors

Answer 21

Heterotrimeric G-protein ; alpha beta and gamma ; BETA AND GAMMA ALWAYS STICK TOGHETHER

Question 22

80% of drugs target them

Answer 22

G-protein coupled receptors

Question 23

Another word for a g-protein coupled receptor

Answer 23

Serpentine receptor

Question 24

Mechanism of action of G protein coupled receptor

Answer 24

7-TM receptor and heterotrimeric G-protein are inactive
Ligand binds and changes conformation of receptor
Unassociated G protein binds to the receptor and GDP is exchanged for GTP which allows beta and gamma to separate from alpha and GTP
Alpha and gtp/beta gamma bind to their target proteins
GTPase acts on alpha subunit causing GTP to go to GDP and alpha unit dissociates from target protein to form the inactive heatertrimeric G protein

Question 25

How long does the receptor remain active for in a G protein coupled receptor?

Answer 25

Receptor remains active as long as ligand is bound and can activate other heterotrimeric G-proteins tooooo

Question 26

What is the target protein that is often targeted by the components of the heterotrimeric G protein?

Answer 26

Adenylyl cyclase

Question 27

Example of a G protein linked receptor that stimulates adenylyl cyclase?

Answer 27

b-andrenergic receptor (this is how adrenaline acts on the heart) ; it converts ATP to cAMP which activates your protein kinase

Question 28

G protein linked receptor that inhibits adenylyl cyclase

Answer 28

M2 muscarinic receptor (parasympathetic nervous system that is continuously keeping your heart rate down) ; this REDUCES levels of protein kinase A

Question 29

Gs/Gi

Answer 29

Stimulatory/inhibitory G protein

Question 30

Gq protein linked receptor

Answer 30

Phospholipase C is what GQ is linked to and this c causes an increase in calcium ; example is angiotensin receptor that causes vasoconstriction - so a common drug target is ACE inhibitors for hypertension

Question 31

Enzyme linked receptors

Answer 31

Ligand binding externally causes receptors to cluster internally which activates enzymes in the cytoplasm ; these enzymes phosphorylate the receptor (which moves receptors into a high energy state) ; signalling proteins are now bound to the cytoplasmic domain (receptors)

Question 32

Insulin receptor is also known as

Answer 32

CD220 antigen

Question 33

Classify insulin receptor?

Answer 33

Enzyme-linked receptor with the ligand being insulin and effect being glucose uptake

Question 34

ErbB receptors

Answer 34

The ligand is an epidermal growth factor/transforming growth factor which causes cell growth/proliferation

Question 35

Intracellular receptors Type 1 is

Answer 35

Cytoplasmic ; receptor in cytosol and associated with heat shock protein ; hsp dissociates and 2 hormone bound receptors form a homodimer which translocates to the nucleus to bind with dNA

Question 36

Intracellular receptor Type 2 is

Answer 36

Nuclear ; bind of hormone ligand to receptor in nucleus which now regulates transcription

Question 37

intracellular receptors - glucocorticoid

Answer 37

Ligand is cortisol/corticosterone and this decreases immune response and increases gluconeogenesis

Question 38

Intracellular receptors - thyroid hormone receptor

Answer 38

Thyroxine and triiodothyronine (T4 and T3) are ligands and the physiological response is growth and development