Download Cell Size and Function

Cell Size and
Function
Biology 11
CHS
Why are cells so small?
 To carry out their work, cells need a
constant supply of materials:
oxygen, water and food particles.
 They need to get rid of waste products
How do materials get in
and out of the cell?
 The cell membrane!
To have an idea of the
problem imagine ….
 A cell as a swimming pool with a
diameter of 50 m.
 You need to swim to the center with a
beach ball (food), and swim back
carrying a lifebuoy (waste) 12 times in a
certain time period to keep the cell alive!
 Imagine a pool that is 100 m instead of
50m!
Volume and surface area
 The volume of any object is the amount
of space it takes up.
 The surface area of an object is the area
of the surface that encloses it.
 What covers the surface area of a cell?
Surface area-to-volume ratio
 The relationship between volume and
surface area changes as the object gets
bigger or smaller.
 This is known as surface area-to-volume
ratio
Observations
 Surface area and Volume both increase
as you add more cells or as the cells
grow
 The ratio of SA to V changes
 The volume increases faster than the
surface area
Structural Adaptations
 A structural adaptation to increase
surface area to volume ratio is to be
rectangular prism and very flat (almost
two dimension).
 A second structural adaptation to
increase surface area is folding as seen
in …
Conclusion
 The surface area in any cell is the cell
membrane. The volume is everything
contained in the cytoplasm.
 Every cell to survive must get raw materials in
such as protein, Oxygen, and glucose.
 Cells must also continually get rid of waste
such as CO2, ammonia, salts.
Conclusion
 The only way to get materials in and out
of the cell….
 As a cell grows it requires a greater
amount of material however there is less
surface area compared to its volume to
allow materials in and out of the cell
membrane.
Calculating Volume
 Volume = height X width X length
 Example  4 cm X 4 cm X 4 cm = 64
cm3
Calculating surface area
 Surface area of a cube = calculate the
area of one side by multiplying width X
height and then multiply by 6 (the cube
has 6 sides).
 Example  : 4cm X 4cm X 6 sides =
96cm2
Surface Area and Volume
of a Rectangle