Cell biology question please help!

Question

A practical was carried examining the effect of drug A on phagocytosis and exocytosis in tetrahymena, following the same protocol you used. The results are shown below.

Treatment	Time point (min)	Number of Tetrahymena counted	Number of red vesicles	Number of black vesicles
EtOH	10	5	10	45
	30	4	40	16
Drug A	10	4	4	32
	30	5	25	35

What was mean number of granules/ tetrahymena excreted by exocytosis in the control and Drug A treated cells from time point 10 min to the end of the experiment?

	A.	8 and 4 respectively
	B.	5 and 1 respectively
	C.	10 and 5 respectively
	D.	4 and 7 respectively

Answer 1

Hey! Okay so I think this paper will help you to understand the experiment. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3366903/

There's a few things that you need to know:

(1) The BLACK vesicles measure EXOCYTOSIS (that just means a cell kicking stuff out). The paper will help explain why. "The process of exocytois in Tetrahymena is easily visualized with a compound microscope by feeding the cells India ink (black) and monitoring the loss of India ink–stained vesicles over time (decrease in the number of black vesicles)". By the way, vesicles? Weird word. Just means little spheres with stuff in them.

(2) The question asks you to compare your group treated with Drug (A) with the control. The control is the EtOH group (that's just the science way of abbreviating"ethanol" which is just the science way of saying "alcohol"). So take a look at the Drug A vs EtOH column.

(3) The question asks you to look at the time BETWEEN 10 and 30 minutes. This means you have to get your answer for 30 minutes and subtract your answer for 10 minutes. For instance, if I personally asked you how many vesicles (CIRCLES!) were collected between 10 and 30 minutes, and there were 100 at 30 minutes at 40 at 10 minutes, you would confidently tell me that 60 had been collected between 10 and 30 minutes.

(4) the number of Tetrahymena is changing. I forgot what those were, actually, but they're little protozoa! So in order to account for that, rather than subtracting the total number of black vesicles (circles) present at 30 minutes and at 10 minutes, subract the number PER tetrahymena. For example, if I personally asked you how many vesicles there were at 30 minutes per tetrahymena with the following data:

EtOH 10 min 3 tetrahymena 33 black vesicles

30 min 2 tetrahymena 20 black vesicles

In that imaginary scenario, you would confidently tell me that at 30 minutes, there were (20/2) = 10 vesicles PER tetrahymena and at 10 minutes there were (33/3) = 11 vesicles PER tetrahymena, and that the mean number of granules excreted between 10 and 30 minutes was (11-10) = 1 vesicle per tetrahymena for the EtOH group.