1.9 Cell Signalling

Question 1

Why do cells need to communicate

Answer 1

Process information

Self preservation

Voluntary movement

Homeostasis

Question 2

Endocrine communication

Answer 2

Hormones travelling by bloodstream from organ of production to effect

Question 3

Example of endocrine communication

Answer 3

In hypoglycaemia glucagon secreted by alpha cells of islets of langerhans in oancreas

Insulin in beta cells of pancreas acting on liver, muscle and adipose

Adrenaline produced in adrenal glands acting on trachea

Question 4

Endocrine signalling

Answer 4

Hormone travels within blood vessels to act in a DISTANT target cell

Question 5

Paracrine communication example

Answer 5

Hyperglycaemia
Insulin released from beta cells in islets of langerhans in pancreas act on adjacent alpha cells to inhibit glucagon secretion

Osteoclast activating factors produced by osteoblasts

NOX produced by endothelial cells in blood vessels

Question 6

Insulin signalling

Answer 6

Endocrine by acting on liver
Paracrine by acting on alpha cells of pancreas

Question 7

Paracrine signalling

Answer 7

Hormone acts on adjacent cell

Question 8

Membrane attached proteins signalling

Answer 8

Plasma membrane proteins on adjacent cells interacting

Question 9

Example of membrane attached protein communication

Answer 9

Blood borne virus detected by antigen presenting cell in blood

APC digest pathogen and express molecules on surface

T lymphocytes engage with molecules through T cell receptor interaction

Question 10

Autocrine signalling

Answer 10

Signalling molecule acts in same cell

Question 11

Example of autocrine communication

Answer 11

T cell receptor activates cascade of reactions within T cell,
Including expression of IL-2 receptor on surface as well as secreting IL-2

Question 12

Types of receptors

Answer 12

Ionotropic

G protein coupled

Enzyme linked

Intracellular

Question 13

Ionotropic receptors

Answer 13

Ligand binding causes conformational change of channel protein opening pore (tunnel)

Ions move accordingly (conc g)

Question 14

Ionotropic receptor example

Answer 14

Nicotinic Ach

Ligand = Ach
Location: skeletal muscle
Effect: contraction muscle

Question 15

G protein coupled receptor

Answer 15

Ligand binding activates transmembranous receptor

Unassociated G protein binds to the receptor

GDP changed for gtp

G protein dissociates to alpha and beta-gamma subunits then a bind to target protein

Gtp de phosphorylated to gdp dissociating alpha subunit - inactive

Question 16

Enzyme linked receptors

Answer 16

Ligand binding causes receptor clustering and activates internal enzymes

Enzymes phosphorylated receptor causing binding of signalling proteins which recruit other signalling proteins

Example: insulin receptor for glucose uptake

Question 17

Intracellular receptor

Answer 17

Type 1- cytoplasmic
Hormone binds to receptor, dissociates hsp
2 hormone bound receptors form a hommodimer which dissociates to the nucleus and binds to dna
Example: glucocorticoids receptor

Type 2- nuclear (faster)
Binding of hormone ligand causes transcriptional regulation
Example: thyroid hormone receptor

Question 18

Types of g protein coupled receptors

Answer 18

Gs

Gi

Gq

Question 19

Gs protein linked receptor

Answer 19

Stimulates adenylyl cyclase to convert atp to cAMP (which then activates PKA)

Example in beta adrenergic receptor

Question 20

Gi protein linked receptor

Answer 20

Inhibits adenylyl cyclase

R3duces levels of PKA

Example: m2 muscarinic receptor

Question 21

Gq protein linked receptor

Answer 21

Stimulates PLC

Examples AT1 angiotensin receptor

Converts PIP2 to IP3 and DAG, stim ca2+ release and activates pkc