Hyper/Hypo osmotic question

[JRod17]

2. A bacterial cell has its cell wall removed and is placed in distilled water. Which of the following will happen?

A. The bacterial cell will lyse because it is hyperosmotic to the water.
B. The bacterial cell will lyse because it is hypoosmotic to the water.
C. The bacterial cell will shrivel because it is isotonic to the water.
D. The bacterial cell will shrivel because it is hypoosmotic to the water.
E. The bacterial cell will shrivel because it is hyperosmotic to the water.

The correct answer is A... although I can't seem to wrap my head around why. My understanding was that a hypO osmotic cell has a higher concentration of solutes on the inside (therefore lower conc. of water compared to outside) and water would flow in causing cell to lyse. Yet the answer is A, hypER osmotic. Where am I going wrong?

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[ilovefruits]

Hey JRod17

I think answer choice A meant the cell has more solutes than the water..even though we usually only talk about the environment being hyperosmotic/iso/hypo. Like, if it says, "a cell is placed in an hyperosmotic environment", that means the cell has less solutes than the surrounding.

2. A bacterial cell has its cell wall removed and is placed in distilled water. Which of the following will happen?

A. The bacterial cell will lyse because it is hyperosmotic to the water.
B. The bacterial cell will lyse because it is hypoosmotic to the water.
C. The bacterial cell will shrivel because it is isotonic to the water.
D. The bacterial cell will shrivel because it is hypoosmotic to the water.
E. The bacterial cell will shrivel because it is hyperosmotic to the water.

The correct answer is A... although I can't seem to wrap my head around why. My understanding was that a hypO osmotic cell has a higher concentration of solutes on the inside (therefore lower conc. of water compared to outside) and water would flow in causing cell to lyse. Yet the answer is A, hypER osmotic. Where am I going wrong?

 

[aznriptide859]

Remember osmolarity refers to the comparison of concentrations between two environments, but it's the solvent that movies, not the solute.

If a cell is placed in a hyperosmotic environment, then the cell is hypoosmotic to that environment, and the environment is hyperosmotic to the cell. Water will flow out of the cell in this case and plasmolyze.

If a cell is placed in a hypoosmotic environment, then the cell is hyperosmotic to that environment, and the environment is hypoosmotic to the cell. Water will flow into the cell in this case and lyse.

Be careful of how the question asks A is compared to B.

 

[KaplanPatrick]

Hey guys!

The wording of the question is going to be VERY important. The DAT will test both the environment or the inside of the cell. The KEY to this question was the wording "distilled water" meaning that it had no solutes in the water. The water is HYPO to the cell. Or the cell is HYPER compared to the water.

A good way to remember this is that HYPO rhymes with LOW and HYPER means HIGH!

Pat

 

[JRod17]

Awesome, I think I've got it now. Thanks for the help!