Cell Growth & Division


-Cell Size Limitations (Why a cell can't grow forever)

-Surface-to-Volume Ratio
     -volume increases faster than surface area

Length of Side Surface Area Volume Surface-to-Volume Ratio
1 mm 6 mm2 1 mm3 6
2 mm 24 mm2 8 mm3 3

 4 mm

96 mm2

64 mm3



          -causes problems with the transport of materials
            -larger cells need more "stuff" but only so much 
             can cross the cell membrane at a time
                  -cell division solves a cell's size problem

a cell needs a large surface area relative to its volume 
         (a high surface-to-volume ratio)
to survive



-The Cell Cycle & Mitosis

-Cell Cycle  (interphase mitosis cytokinesis)
     -the time required for a cell to reproduce itself
          -varies depending on the type of cell

                    mitosis is only one part of the cell cycle



-Stages of Interphase 

     -interphase = period between cell divisions

-Gap 1 (G1)
     -cell growth & development
-DNA Synthesis (S)
     -replication of DNA
-Gap 2 (G
     -creation of materials needed for division

Doubling the nuclear material in the S-phase provides enough DNA to generate 2 complete nuclei at the end of mitosis.  This ensures that each daughter cell has the same number of chromosomes as the original parent cell. 



-Stages of Mitosis

     -mitosis = division of the nucleus

     -chromosomes form
     -nuclear membrane breaks down
     -spindle forms
     -chromosomes line up in the center of the cell
     -centromeres split and chromatids are pulled to
      opposite ends of the cell
     -spindle breaks down
     -chromosomes unwind
     -nuclear membrane reforms

telophase is essentially the opposite of prophase


-Methods of Splitting the Cell

     -cytokinesis = division of the cytoplasm

-Plant vs. Animal Cells
     -animal cells form a cleavage furrow
-the cell membrane pinches inward
     -plant cells form a cell plate
-the rigid cell wall prevents an inward pinch

  a "figure-eight" shape indicates a cleavage furrow



  to great cell cycle graphics

-Cells Alive (animated)
-UNC Charlotte
     -photos (plant & animal)

to more detailed notes

-Molecular Expressions (diagrams included)
-California State University, Chico (animated)
-Molecular Biology Notebook Online (drawings included)