Cell Size Lab
INTRODUCTION:
It is through the cell membrane that food, oxygen, and
water enter the cell and waste products leave the cell.
How quickly this exchange takes place depends on the
surface area of the
cell membrane. The amount of food and oxygen needed
and the amount of waste produced depends on the volume
of the cell. When cells grow to a certain size, their
rate of growth slows
down and then stops. They have reached their size
limit. When one of these larger cells divides into two
smaller cells, the rate of growth again increases. In
this investigation you will experiment
to determine why this is so.
EQUIPMENT AND MATERIALS:
250 ml beakers
agar-agar
Plastic spoon millimeter ruler
Phenolphthalein
razor blade
11" X 13" pan
4% NaOH solution
paper towels
PROCEDURE:
1. Obtain an agar block from your teacher.
2. With a razor blade, cut your block in half. Set
one half aside and cut the remaining block in half
again. Set one half aside and repeat this process
until you have five different sized blocks.
3. As you cut the blocks, measure and record their
length, width, and height on the data table.
4. When all the blocks have been measured and
recorded, submerge them in NaOH solution. Use caution
with NaOH-it is caustic. If NaOH gets on you, wash it
off immediately.
5. Allow the cubes to soak for 5 minutes, then pour
the NaOH down the sink and rinse the cubes with water.
Use care that you do not pour your agar cubes out of
the beaker. Now remove the agar cubes with a spoon and
blot them dry with a paper towel.
7. With your razor blade, cut the agar cubes in half
and measure the depth of the colored area. This is
known as the amount of absorption and should be
recorded in the mm Absorbed column.
Observations:
Using your measurements, determine the surface area,
volume, and surface area to volume ratio of each block
and record it on the data table.
Surface area (mm2) = L x W
6 numbers together.
of each side, then + the
Volume (mm3) = L x W x H
Surface area to volume ratio = surface area /
volume
DATA TABLE
Cube
Surface
Dimension Area
L, W, H
(mm2)
(mm)
Volume
(mm3)
L x W x H
S.A./Volume mm
ratio
Absorbed
QUESTIONS:
1. Which cube has the greatest surface area?
2. Which cube has the greatest surface area to volume
ratio?
3. What evidence is there that sodium hydroxide is
being absorbed by the agar cubes?
4. Explain how cells “feed” themselves.(obtain
nutrients and get rid of wastes)
5. If the sodium hydroxide were some vital substance,
such as food, and the agar cubes were cells,which cell
would be “fed” the most efficiently?
6. What happens to the surface area to volume
a cell as the cell grows?
7. What happens to the cell’s ability to feed
and get rid of waste as it grows?
8. What happens to the surface area to volume
you divide the cell in half?
9.
Make a statement which explains why cells
limited in the size to which they can grow.
ratio of
itself
ratio if
are