Lecture 8 - cell communication

Question 1

Local signalling

Answer 1

Acts on nearby target cells; can act on signalling cell

Question 2

Long distance

Answer 2

Hormones travel through circulatory system to act on far away target cells (insulin)

Question 3

3 main steps of signalling

Answer 3

Reception, Transduction; Response

Question 4

Reception

Answer 4

involves receptor protein and signalling molecule binding so receptor changes shape or chemical state

Question 5

Transduction

Answer 5

Altered receptor protein activates another protein which can cause a cascade of changes often via phosphorylation

Question 6

Second messengers

Answer 6

Relay molecules (e.g. cAMP IP3, Ca2+)

Question 7

Response

Answer 7

When cell actually does something, activated proteins will cause at least one function to occur in the cell

Question 8

Membrane bound vs non membrane bound receptors

Answer 8

Receptors of water soluble molecules are membrane bound (hydrophilic); receptors of lipid soluble molecules are not membrane bound (hydrophobic) and in cytoplasm or nucleus

Question 9

Examples of membrane bound receptors

Answer 9

Ligand gated ion channels, G protein coupled receptor, tyrosine kinase receptor

Question 10

Examples of lipid soluble hormones

Answer 10

Testosterone, progesterone, estrogen, thryoid hormones

Question 11

Which body system relies heavily on ligand gated ion channels?

Answer 11

Nervous system - neurotransmitters bind to ligand gated ion channels on target cells which propagate action potentials

Question 12

Protein kinases

Answer 12

Enzymes which activate relay molecules by transferring a phosphate group from ATP to the protein (phosphorylation)

Question 13

Phosphatases

Answer 13

Deactivate (but recyclable) relay molecules by removing phosphate from the protein

Question 14

cAMP signal pathway

Answer 14

GCPR activates adenylyl cyclase –> cAMP is converted from ATP by adenylyl cyclase –> activates downstream proteins as second messenger

Question 15

Ca2+ as second messenger requirements

Answer 15

Needs to be pumped out of cell or into ER or into mitochondria to maintain low conc Ca2+ in cell and high conc outside of cell

Question 16

Ca2+ and IP3 signal pathway

Answer 16

G protein coupled receptor activates phospholipase C –> cleaves PIP2 into IP3 and DAG –> IP3 binds to gated channel of ER –> Ca2+ diffuses into cytosol activating other proteins –> cellular response

Question 17

benefits of phosphorylation cascade (multi steps)

Answer 17

Amplification, control points, specificity (temporal, spatial) of response despite common molecules, coordinate with other signalling pathways

Question 18

Phosphodiesterase (PDE)

Answer 18

breaks down cAMP to deactivate response

Question 19

Adrenalin pathway

Answer 19

Ephinephrine binds to GPCR –> adenylyl cyclase –> ATP to cAMP –> two protein kinases –.> lots og glycogen to glucose 1-phosphate. Each step mega amplification

Question 20

Glycogen to ATP

Answer 20

Glycogen -> glucose 1-phosphate -> glucose 6-phosphate

Question 21

Specificity of receptors

Answer 21

3D shape means structure determines function, only target cells interact with ligand

Question 22

Types of local signalling molecules

Answer 22

Growth factors: Fibroblast Growth Factor (FGF) paracrine

Neurotransmitters: acetylcholine (synaptic)