Lecture 28

Question 1

enzyme-coupled receptors are

Answer 1

• transmembrane proteins that act as enzymes or associate with another protein that acts as an enzyme
• response are usually slow and usually result in gene expression

Question 2

What is the largest class of enzyme couples receptors

Answer 2

• receptor tyrosin kinsases (RTKs)
• they are single pass transmembrane proteins
• the receptors often form dimers upon binding with extracellular signalling molecules
• tyrosine residues on cytoplasmic tails are phosphorylated which serve as docking sites for other proteins

Question 3

RTKs are ______ transmembrane proteins

Answer 3

single pass

Question 4

interaction domain

Answer 4

• recognize phosphorylated tyrosine on the tail

Question 5

Termination of the signal

Answer 5

• protein phosphatases dephosphorylate the tyrosines
• others are endocytosed and destroyed by the lysosomes

Question 6

RTKs activate

Answer 6

• the monomeric GTPases Ras
• Ras-GEF : encourages Ras to exchange GDP for GTP which activates Was
• Ras-GAP: which inactivates Was by promoting GTP hydrolysis

Question 7

Example of phosphorylation cascade

Answer 7

• Mitogen activated protein kinase (MAP kinase) pathway

Question 8

Mitogen is

Answer 8

mitogen is an extracellular signalling molecules that stimulates cell proliferation

Question 9

what happens when cancers involve mutation in RAS

Answer 9

• it inactivates GTPases
• this prevents cell from being turned off and results in uncontrolled proliferation

Question 10

oncogene

Answer 10

• a gene that when activated can potentially make a cell cancerous