Part A. True or False
As indicated on your Parscore sheets, fill in A for True or B for False.

1. The efficacy of an agonist is determined in large part by the number of available or "active" receptors with which to bind. TRUE!

2. The Ras-Raf-MAP kinase pathway is activated upon stimulation of receptor tyrosine phosphatases. FALSE! (kinase, Trk-Rs)

3. Intracellular signaling through Gq-coupled receptors does not involve direct activation of second messenger systems. TRUE! ... (PLC-BETA → PI(4,5)P2 → DAG/IP3 → then Ca2+.... PKC)

Multiple Choice Answers (1 mark each):
You are to select the BEST of the lettered alternatives provided for each question. Fill in the appropriate selection on your Parscore sheet. Choose only ONE answer for each question. Each question is worth 1 mark each.

4. Of the following, which is TRUE regarding receptors?
a) A receptor has an endogenous ligand that interacts with a specific site on the receptor.
b) The capacity of a ligand to bind to a receptor is determined by the charge, shape and size of both the ligand and the receptor.
c) The intensity of the effect of the binding of a ligand to a receptor depends upon the percent of total receptor occupied by the ligand.
d) All of the above.

5. Activation of which of the following kinases is dependent upon intracellular cAMP levels?
a) protein kinase A (PKA)
b) protein kinase C (PKC)
c) mitogen-activated protein kinase (MAPK)
d) calcium-calmodulin kinase II (CAMK II)

Open-ended Questions. Good answers should be concise and logically organized. Answers should be written on each page under the appropriate question and can continue to the back if necessary. Answers can be in point form or can be illustrated but the information MUST be complete in order to receive full marks. Use the number of points awarded for each question as a guide for the number of steps involved. You have a full page to answer each question below but should you need more space, please use the back of the page but INDICATE so (or else a portion of your answer may be missed).

6. Explain in detail at least 2 ways in which stimulation of a receptor tyrosine kinase could lead to an increase in CREB-mediated transcription of a gene . (16 marks)