Lecture 9

Question 1

What can extracellular mediators modify in the plasma membrane?

Answer 1

Function, movement, Cellular metabolism

Question 2

What can extracellular mediators modify in the nuclear membrane?

Answer 2

Gene expression, development

Question 3

Describe basic diagram of signal tranduction

Answer 3

Hydrophobic signal e.g. steroids, thyroxine, retinoids bind cytosolic receptor in plasma membrane

Bound receptor crosses nuclear membrane to generate response

Question 4

What are the 3 types of cell-to-cell signalling

Answer 4

Endocrine - Long range, blood borne hormones

Paracrine - Short range, localised action growth factors and cytokines

Autocrine - Same cell, growth factors and cytokines

Question 5

What are the 3 types of extracellular mediator?

Answer 5

Hormones - Endocrine action, blood borne, Generally short term metabolic effects

Growth factors - Paracrine or autocrine action, Long term proliferation/developmental effects

Steroid hormone - Intracellular receptors, autocrine, long term effects

Question 6

Paracrine action of extracellular mediators

Answer 6

Paracrine acting factor secreted from secretory vesicle on secretory cell

Binds receptor on adjacent target cell

Question 7

What are G-protein-coupled receptors involved in?

Answer 7

Metabolism, movement, short-term changes in cell function

Question 8

What are enzyme-coupled receptors?

Answer 8

Receptors with intrinsic enzyme activity

Receptor serine-threonine kinases e.g. TGF-beta receptors

Receptor tyrosine kinases

Cytokine receptors (Interleukin-3 receptor)

Receptor associated kinases - long-term change in gene expression or development

Question 9

Ion channel receptors

Answer 9

Ligand gated ion channels

Transient receptor potential (TRP) channels

Question 10

What are second messengers?

Answer 10

Intracellular metabolite or ion - couples extracellular stimulus to physiological response

Question 11

Criteria for classification of second messengers

Answer 11

• Small molecule
• Mechanism that induces rapid alterations in concentration
• Controlled by extracellular stimuli
• Regulate enzyme or protein activity
• Involve highly specific interactions
• Amplification present in system

Question 12

Examples of secondary messengers

Answer 12

Cyclic nucleotides - cAMP, cGMP

Lipid-derived messengers - DAG, IP3

Question 13

Explain what cAMP does

Answer 13

• Activates protein kinase A
• Increases lipid breakdown
• Decreases glycogen synthesis

Question 14

What does cGMP do?

Answer 14

• Activates protein kinase G (PKG)
• Opens cation channels in rod cells

Question 15

What does 1,2-diacylglycerol (DAG) do?

Answer 15

• Activates protein kinase C
• Decreases glycogen synthesis
• Increase transcription

Question 16

What does Inositol 1, 4, 5-trisphosphate (IP3) do?

Answer 16

• Opens calcium ion channels in endoplasmic reticulum
• ca2+ important secondary messenger
• Activates Ca2+ dependent protein kinases

Question 17

Protein phosphorylation

Answer 17

R-OH —-> Protein kinase and ATP hydrolysis —-> R- PO4

R-PO4 —-> Protein phosphatase and H2O -> Pi —->R-OH

Question 18

What enzyme catalyses serine to phosphoserine?

Answer 18

Tyrosine kinase

Question 19

Serine/threonine kinases and their activating signals

Answer 19

cyclic nucleotides - cAMP dependent protein kinase, cGMP dependent protein kinase

Ca2+ and calmodulin - Ca2+-calmodulin protein kinase, Phosphorylase kinase, glycogen synthase kinase 2

AMP - AMP-activated kinase

Diacylglycerol - protein kinase C

Metabolic intermediates - Many target-specific enzymes e.g. pyruvate dehydrogenase