2. Student Goals Explain the purpose of cell division
Identify the steps and events of each cell phase.

3. Cell Size
Cell size is constrained by cellular needs for raw materials and the chemical properties of molecules.
too big = can’t get enough matter and energy or get rid of chemical wastes
too big = too many demands on DNA – things get out of control
Sometimes, smaller is better
Which nucleus is bigger?
They are exactly the same size.

4. Life of a Cell Cells lining the esophagus live for 2-3 days
Cells lining the small intestine live 1-2 days
White blood cells may live for only 10 hrs, or for decades
Red blood cells live less than 120 days
Muscle cells live for years
Nerve cells live for many years

5. Cell Life
Most of the time that a cell is alive, it is busy growing, making molecules and using them.
This is called Interphase (the time between mitotic divisions)
The DNA is strung out in the nucleus, invisible. (chromatin)
When the cell reaches its size limit, it gets ready to divide in two in a process called mitosis.
Before that can happen, the DNA and all the cellular organelles are replicated during interphase.

6. Life Cycle of a Cell
Interphase – growth, increase in size, and synthesis of organelles and molecules G1 S G2
Mitosis - Cell division
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis

7. The Big Picture
One cell becomes two Each with the same number of chromosomes as the Parent cell

8. The Big Picture- 2
Before PROPHASE the chromatin is replicated (copied).
During PROPHASE it condenses into chromosomes.
Each chromosome has a replicated twin = sister chromatids.
These are the 46 chromosomes in a human cell as mitosis begins.

9. Chromatin > Chromosome > Chromatids
Chromatin, Chromosomes, and Chromatids are all the same– named differently depending on the stage.
Chromatin
Chromosome
Chromatids
Differences between Chromatin/Chromosomes/Chromatids

10. 1. Prophase Pro = pre (before)
2. Metaphase
Meta = middle
3. Anaphase
Ana = apart
4. Telophase
Telo = two
5. Cytokinesis
Cyto = cell,
kine = move

11. Mitosis: What does it look like?
Identify each stage from the pictures

12. Mitosis: What does it look like?

13. Mitosis: What does it look like?
Examine Allium root tips under the microscope and identify the parts.

14. Mitosis: What does it look like?

15. Quiz yourself
Check out this website! (biologycorner.com) For a REVIEW and practice quiz!
Practice Quiz on Discovery Education