Lab Quiz #1 Key

Picture of a plant cell, pointing to a cell wall.

1. What is the name of this structure?

[Cell wall – (plasma membrane also OK)]

2. You perform the Egg Lab and come up with the data below. Which beaker (X or Y below) contains the solution that is hypotonic to the egg? Explain how you can use the data to determine this.

Egg in Beaker X

Weight before soaking in beaker = 88 g

Weight after soaking in beaker = 82.5 g

Egg in Beaker Y

Weight before soaking in beaker = 88 g

Weight after soaking in beaker = 97.2 g

[Beaker Y. The hypotonic solution has fewer solutes (so more water), than the egg (“cell”), which has more solutes (less water). In the hypotonic solution the water will enter the “cell” (diffusing down its concentration gradient), which will increase its weight.]

Picture of a cheek cell, pointing to a nucleus.

3. What is the name of this structure?

[nucleus]

Picture of a beaker with two different solutes, labeled side A and side B.

4. Given that:

•The membrane separating Side A & Side B is only permeable to the triangular solutes.

•At Time 1, the triangular solutes were added to Side A and the round solutes were added to Side B.

Question: at Time 2 (5 mns later):

A)what will happen to the triangular solutes in terms of diffusion?

[Some triangles will diffuse from Side A to Side B, equalizing out their concentration gradient between the two sides.]

B)what will happen to the round solutes in terms of diffusion?

[Round solutes will stay on Side B – no path]

Picture of a beaker with two different solutes, labeled side A and side B.

5. Given that:

•The membrane separating Side A & Side B is only permeable to the triangular solutes.

•The membrane is also permeable to water.

•At Time 1, the triangular solutes were added to Side A, and the round solutes were added to Side B.

Question: at Time 2 (5 mns later) what will happen in terms of osmosis?

[More water will move from Side A to Side B. More solutes are now on Side B (all the rounds plus ½ of the triangles), so less free water on Side B. Water will diffuse down its concentration gradient to Side B. (Remember that in general water follows solutes.)]

6. What is the function of this structure?

[stores starch]

7. When putting the microscope away, which objective should be in place?

[scanning or lowest power]

8. What types of information should be recorded when making good observations?

[Name of organism, magnification/size, color, texture, shape, patterns, etc.]