Download Biology 2201 Name: Limits to Cell Size

Biology 2201
Name:________________
Limits to Cell Size
Introduction
Why can’t cells continue to grow larger to become giant cells? Why are
most cells, whether they’re from an elephant or an earthworm, about the
same size? Why would cells continually grow and divide to become two
smaller cells?
Purpose
To simulate the changing relationship of surface area to volume for a
growing cell.
Materials
3 spherical items
Tape or string
Calculator
Procedure
This activity is designed to give you a hands-on appreciation of the
relationship between surface area and volume which is so critical to
understanding the limits of cell growth.
3 cubic items
Ruler
Before you begin, you will need to find 3 spherical and 3 cubic objects in
your house or around the school. It doesn’t matter if they are perfectly
spherical or cubic; we will just assume they are in all calculations. These
three spheres and cubes represent growing cells.
Design a table and present the results of 1-8 in your table:
1.
2.
3.
4.
5.
6.
7.
8.
Find the circumference of the three spherical objects. Use a piece
of string or tape to measure.
Calculate the radius of each one using the formula C=2Br
Find the surface area of each using the formula
SA= 4Br2
Find the volume of each one using the formula
V=4B3/3
Calculate the ratio of surface area to volume
Ratio=SA/V
Now find the surface area of the cubic objects
SA=6(l x w)
Find the volume of the cubic objects
V= l x w x h
Calculate the ratio of surface area to volume
Ratio=SA/V
( Table values will vary according to objects chosen)
Analysis
1.
If the spherical objects represent growing animal cells, which cell
has the greatest surface area? Greatest volume? (Answers will
vary)
2.
If the cubic blocks represents growing plant cells, which cell has
the greatest surface area? Greatest volume?(Answers will vary)
3.
Which spherical object has the greatest SA/V ratio? Which block?
(Answers will vary, but the smallest should have the greatest)
4.
What happens to the SA/V ratio as the cell grows (gets bigger)?
(As the cell gets larger, the SA/V ratio decreases )
5.
How will growth in an animal cell affect cell processes? (Think:
osmosis and diffusion) (If the cell is too big, the surface area will
not be large enough to permit everything to diffuse through the
increased volume of the cell)
6.
Which size in both plant and animal cells is most efficient at
permitting materials to enter and leave the cell? ( the smallest )
7.
Write a summary statement explaining how SA/V ratio limits
growth of an individual cell.
(Once the available SA cannot permit substances to diffuse
throughout the entire volume of the cell, the cell will suffer, the
cell must divide before this point is reached )