Question

4. Where are steroid hormone receptors generally located and where do they bind the steroid hormone once it enters a cell?
a. They are located at the cell surface and bind steroids outside the cell
b. They are located in the cytoplasm and bind steroids in the cytoplasm
c. They are located in the cytoplasm but bind steroids within a nucleus after the steroid triggers the receptor translocation
d. They are located in the cell plasma membrane and bind steroids within the hydrophobic part of the membrane

13. Which of the following molecules or proteins are NOT commonly considered a second messenger in signal transduction cascades?
1. diacylglycerol (DAG). 2. nitric oxide (NO). 3. cyclic AMP (cAMP). 4. Sodium ions, 5. Phosphoinosotide 3-kinase (PI3K). 6. Phospholipase C
a. 1, 3 and 5
b. 2, 4 and 6
c. 4, 5 and 6
d. 1, 2 and 3
e. 2, 4 and 5

11. You are studying a human cell cycle protein commonly mutated in cancer cells. you express this protein and find that the cells start to divide faster. You decide to use this system for screen for a drug that may inhibit the activity of this protein. Of the following scenarios, which one suggests you have identified an inhibitor of the human protein?
A. You identify temperature sensitive mutations of the gene encoding the yeast ortholog of the human protein and look for cell death at the restrictive temperature in the presence of a drug
B. You identify temperature sensitive mutations of the gene encoding the yeast ortholog of the human protein and look for cell death at the restrictive temperature in the presence of a drug
C. You identify a drug that increases expression of the protein in yeast
D. You identify a drug that causes yeast cells expressing the protein to grow normally

Answer 1

Question 4 :-

Steroids hormone receptors are of two types. They are either located in the nucleus and remain in the nucleus where hormone comes and bind them or they are located in the cytosol and move to nucleus after binding of hormone.

Now from the given options, the are two candidates : Option B and Option C. But option C is wrong because it says that Even though receptor is in cytoplasm, it binds Hormone inside the nucleus. This is a False statement as hormone comes from outside the cell for those receptors which are in the cytoplasm

So the right option is Option (B) They are located in the cytoplasm and bind steroid in the cytoplasm.

Question 13:-

Now out of the options given, DAG, Nitric Oxide and cAMP are all secondary messengers while PI3K and Phospholipase C are membrane bound enzymes which are involved in signal transduction but they are not themselves messengers, instead they are generate secondary messengers directly or indirectly. Meanwhile Sodium ions are involved in action potential of cells.

So the right option is Option (C) 4, 5 and 6

Question 11 :-

The right option is Option (D) You identify a drug that causes yeast cells expressing the protein to grow normally.

Explanation :

Since you're Trying to identify a drug which can treat human protein mutation you've to find a drug which reverses its effects. Now the effect of the human protein is cancer cell (Unlimited cell proliferation) so the opposite of this effect is normal dividing cells.

So if you've found a drug which inhibits the protein in the question, it will make the cell divide normally.