1. Cell Size Limitation Notes

2. Cell Size limitations The cell theory (1838) states:
The cell is the basic unit of life
All living things are composed of cells
All cells come from pre existing cells

3. Remember!
Materials are moved in and out of cells through the process of diffusion:
Diffusion is the tendency for particles of any kind to spread out spontaneously to regions where they are less concentrated
Requires no energy

4. Cell Size Limitations Getting things into cell at an efficient rate
Nutrients
Water
Oxygen
Removing things from the cell quickly
wastes
DNA limits cell size
If cell is too big then DNA cannot make enough proteins to support the cell

5. Cell Size Limitations
Cells divide when the area of their cell membrane becomes too small to service the metabolic needs of the cell
Cell size is limited by a surface to volume ratio
As a cell gets larger, this ratio gets smaller, resulting in cell death because materials cannot diffuse across the cell membrane efficiently

6. Limits Lower limits of cell size: Upper limits to cell size:
At a minimum, a cell must be large enough to house requires material (DNA, protein) to survive and reproduce
Upper limits to cell size:
The maximum size of a cell is limited by the amount of surface needed to obtain nutrients from the environment and dispose of waste

7. Surface area to volume ratio limits size

8. What limits the size of cells?
Surface Area to Volume Ratio - How much space is on the outside (cell membrane) compared to the space on the inside of the cell.
As the surface area of something increases, it’s volume increases faster
Surface area = L x W x # of sides (cm2) the surface of an object. The outside covering of a cell. (cell membrane)
Volume = L x W x H (cm3) The space inside the cell
A small object has a high surface area to volume ratio ex: 6/1
A large object has a small surface area to volume ratio ex: 24/8

9. It takes more time for the nutrients to reach the center of this cell
Large Cell
It takes more time for the nutrients to reach the center of this cell

10. Smaller cell
It takes less time for the same nutrients to reach the center of this cell

11. Answers Not enough nutrients in fast enough
As a cell gets larger which increases at a faster rate, the surface area or the volume?
Volume
If a cell were larger, would it’s interior structures be closer or further from the cell membrane?
Further
What problems might occur if cells were too large?
Not enough nutrients in fast enough

18. Cell Size Limits Are whale cells the same size as starfish cells?
Yes!

19. Conclusion
As cell size increases, the surface area to volume ratio Decreases (small surface area to volume ratio), which can lead to death of a cell.
Having a large surface area to volume ratio is important to the functioning of cells since it gets materials, nutrients, O2, & wastes into & out of it faster.
Cells divide before they get too big!