Cell shape and size can affect the rate of transport of materials into and out of cells. A higher ratio of surface area to volume allows for more efficient transport, and spherical shapes like golf balls have a higher SA:V ratio than larger shapes like basketballs due to the relationship between surface area and volume as objects increase in size. Maintaining a small size is important for most cells to facilitate transport through the cell membrane.

1. There are lots of materials moving in and out of cells. What
factors can affect how quickly this transport occurs?
Take 3 minutes and brainstorm in your groups.
Image by Neodop

2. Cell shape influences the rate of
transport

3. Which of the following shapes has the largest
ratio of Surface Area /Volume?
A) Basketball
B) Baseball
C) Golf Ball
What happens to an object’s surface
area/volume ratio as it increases in size?
Surface Area2
Volume3
Which will increase
faster, the
numerator or the
denominator?

4. Equations
• For spheres…
A = 4•π•r2
V = 4/3•π•r3

5. Ball
SA
(cm2)
V
(cm3)
SA/V
Golf 12.56 4.18 3
Basket
ball
452.4 904.8 0.5

6. The largest animal cell: neuron of the giant squid
1 mm
Most cells are super small!
This allows them to maintain a high SA:V, which facilitates
moving materials in and out of the cell.
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