Transcript Cell Size Limitations Notes1

Cell Sizes &
Growth
Limitations
Cell Size and Limitations
1. Diffusion limits size
2. DNA content limits size
3. Surface area to volume ratio limits size
Diffusion limits size
• An oxygen molecule follows a path to the mitochondria
(Oxygen)…
plasma membrane  cytoplasm  mitochondria
• Because of the small size of the cell, oxygen
molecules take a fraction of a second to reach the
mitochondria.
• Smaller size allows the cell to be more efficient
DNA content limits size
• Cells usually contain only one nucleus
•DNA
•DNA
•RNA
•RNA
•DNA
is found in the nucleus
makes RNA
will travel through the cytoplasm to the ribosomes
assists the ribosomes in making proteins
is responsible for the whole above process
• If the cell was very large, there would not be enough
DNA to support the cell.
Surface area to volume ratio limits size
• As a cell increases, it volume increases much faster
than its surface area
• If a cell doubled, the cell would require 8X more
nutrients and have 8X more waste to get rid of
FYI – If E.coli were left unreglated, it could
engulf the Earth in one day because it doubles in
volume every 30 minutes!!
When do cells divide?
• All organisms grow and change.
• Cells are constantly growing, dividing, and dying
• Some cells divide more than others –
•Heart & nerve system cells rarely (if ever)
divide
•Skin cells, on the other hand, are constantly
dividing
•Growth is related to cell specificity and activity
•If cell growth is uncontrolled – leads to cancer