cell signalling - week 2 - part 2

Question 1

what do all hydrophilic signalling molecules - except gases- have to do?

Answer 1

bind cell surface receptor proteins

Question 2

What is a primary messenger?

Answer 2

the signalling molecule trapped outside the cell

Question 3

What is the process of transmembrane signal transduction?

Answer 3

• passing along of the signal
• binding of 1st to cell surface receptor generates intracellular 2nd (ion or mol) that relays signal form outside to inside of target cell

Question 4

How do 2nd messengers change the function of the target cell?

Answer 4

• activate protein kinase enzymes
• these transfer phosphate anions form ATP onto an amino acid side chain in intracellular target proteins

Question 5

What three amino acids can protein kinase only add phosphate ions onto?

Answer 5

serine (ser)
threonine (thr)
tyrosine (tyr)

Question 6

Why can protein kinases only add phosphate ions onto three aa’s?

Answer 6

• condensation reaction between phosphate ion and aa requires presence of pilar hydroxyl group into aa side chain

Question 7

Why can only tyrosine kinase enzymes break down tyrosine not threonine/seronine which can be broken by same enzyme

Answer 7

due to having to accommodate the phenol ring in the side chain of tyrosine

Question 8

Why are serine/ threonine/ tyrosine residues only weakly hydrophilic?

Answer 8

due to hydroxyl dipoles in their side chains