1. Cell division

2. Why do cells need to divide?
The cell membrane is permeable to some substances (semi-permeable) and all nutrients and wastes must pass through it
As cells grow (increased volume), the number of organelles increases – so they require more supplies: nutrients and oxygen
As the cell gets bigger, the volume increases faster than the surface area of the membrane

3. As cells increase in size, the surface area-to-volume ratio decreases.

4. This holds true for any cell shape!

5. At a certain size, there is not enough surface area for nutrients/wastes to cross that is required by the cell
So a cell divides into smaller cells in order to allow enough surface area to suit its needs

6. Functions of cell division
Growth – multi-cellular organisms can get larger
Repair – help organisms heal (e.g.cut or broken bone)
Reproduce – so organisms can produce offspring

8. A cell cannot just break in two!
Why?
There is only one nucleus! Which is not always in the middle of the cell The contents (chromosomes / DNA) are not organized for easy division
Cell Division includes a multistep process called MITOSIS.
The 1 cell before it divides is called the parent cell.
The 2 new cells are called daughter cells.

9. The Cell cycle
The cell cycle has 3 parts: Interphase, Mitosis, and Cytokinesis
Mitosis has 4 phases.

10. The steps MITOSIS Interphase Prophase Metaphase Anaphase Telophase
Cytokineseis – division of the cytoplasm
MITOSIS
I – PMAT – C for short

11. interphase
Centrioles
Duplicated DNA
Cell
Membrane
Nucleus

14. PROPHASE
Fragments of nuclear membrane

15. METAPHASE
Mitotic Spindle

16. anaphase
Daughter chromosomes

17. telophase

18. Cytokinesis – animal cells
Cleavage furrow

19. Cytokinesis in a human kidney cell

20. Cytokinesis – plant cells
Instead of “pinching”, a cell plate forms which separates the two new nuclei
This cell plate becomes a new cell wall

21. Cell plate formation

22. The Cell Cycle