1. The Cell Cycle – Stages of growth and division of a cell

2. Where it all began…
You started as a single cell, smaller than the period at the end of a sentence.
And now look at you!
How did you get from there to here?

3. Getting from there to here…
From 1 single cell – a fertilized egg – to baby
The original cell has to divide…
And divide….
And divide…

4. Why do cells divide? For reproduction For growth For repair & renewal
Asexual reproduction – 1-celled organisms
For growth
From fertilized egg to multicellular organism – You!
For repair & renewal
Replace cells that die from normal wear and tear or from injury

5. Why do cells divide? Volume of Cell
Determines the amount of:
Food needed
Waste created
Bigger cells need more food and create more waste!
Surface Area of Cell (cell membrane)
Determine the amount of:
Food a cell can take in
Waste a cell can release

6. Why do cells divide? Ratio of Surface Area to Volume (SA:V)
Comparing the surface area to the volume
As the cell gets bigger, its volume increases faster than the surface area.
This will create problems, as the big cell may need more food than it can take in and create more waste than it can release.

7. Surface Area vs. Volume

8. Why can’t a cell grow indefinitely?
It would require too many nutrients and produce too much waste
Example 1: Big egg vs. Little egg
Example 2: Mr. Kunz vs. 2 year old

9. Why can’t a cell grow indefinitely?
It would be difficult to transport substances within the cell
It would take too long!
It would take too much energy!
Example: You have to go from the center of Plano to the edge of Plano vs. the center of Chicago to the edge of Chicago

10. Why can’t a cell grow indefinitely?
DNA would be overloaded/overworked
All cells have DNA (deoxyribonucleic acid)
The “instructions” for the working cell
As a cell gets bigger, it still only has one set of instructions for the entire cell
Example: A manager who has to tell 10 workers in one room what to do vs. a manager who was to tell 10 workers throughout an entire building what to do

11. Cell Division
Cell Cycle – the process of growing, copying, and dividing
Cell Division – the process by which a cell divides into two new daughter cells

12. The Cell Cycle 3 Steps Interphase - Growth phase
Mitosis – Division of the nucleus
Cytokinesis – Division of the cytoplasm

13. Cell Cycle Cell Division
During the cell cycle, the cell grows, replicates its DNA, and divides into two daughter cells. DNA synthesis takes place during the S phase. Cell division takes place during the M phase. G1 and G2 are gap phases. *

14. Interphase – Growth Phase
Step 1 – G1 Phase
Grows to its full size and produces the additional organelles
Think “G” = Growth
Step 2 – S Phase
DNA synthesis
Chromosome replication
Step 3 – G2 Phase
Prepares to divide
Makes centrioles

15. What are chromosomes? Chromosomes – DNA tightly coiled around proteins
Sister Chromatids – Identical copies of the DNA
Made in S Phase
Held together by a centromere

16. Chromosome Structure

17. Mitosis – (PMAT)
Mitosis – Nucleus divides into two new nuclei and a copy of DNA is distributed into each daughter cell
Prophase
Metaphase
Anaphase
Telophase

18. The Cell Cycle: Interphase, Mitosis, and Cytokinesis

19. Mitosis – Nuclear Division
Prophase
Chromatin condenses into chromosomes
Centrioles move to opposite ends of the cell
Nuclear membrane breaks down
Spindle starts to form

20. Mitosis - Nuclear Division
Metaphase
Chromosomes line up in center of cell
Spindle fibers connect to the centromere of each chromosome

21. Mitosis – Nuclear Division
Anaphase
Chromosomes separate and become single chromatids
Chromatids move to opposite ends of cell

22. Mitosis – Nuclear Division
Telophase
Chromosomes gather at opposite ends of the cell
Two new nuclear membranes form

23. Cytokinesis – Cytoplasm Division
The cytoplasm pinches in half
Each daughter cell has identical set of DNA

24. The Cell Cycle: Interphase, Mitosis, and Cytokinesis

25. Cytokinesis – Animal Cells vs. Plant Cells
In plant cells, a structure known as the forms between the newly divided nuclei.
Cell walls then form on either side of the cell plate

26. Regulating the Cell Cycle
Controls on Cell Division
Experiments show that normal cells will reproduce until they come into contact with other cells

27. The Role of Cyclins
The cell cycle is controlled by a series of checkpoints
Cyclins – proteins that bind to enzymes during interphase and mitosis, signaling the start of various activities
Start of the cell cycle, DNA replication, division of nucleus, etc.

28. The Role of Cyclins

29. The Role of Cyclins Internal Regulators External Regulators
Respond to events inside the cell
Allow the cell cycle to proceed only when certain processes have happened inside the cell
External Regulators
Respond to events outside the cell
Tell cells to speed up or slow down the cell cycle

30. The Role of Cyclins
When cells do not respond to the internal or external regulators, the growth and division of the cell is now uncontrolled (oh no!)
Cancer – uncontrolled growth and division of cells
In a normal cell, when DNA gets damaged the cell either repairs the damage or the cell dies.
In cancer cells, the damaged DNA is not repaired, but the cell doesn’t die like it should.
Instead, this cell goes on making new cells that the body does not need. These new cells will all have the same damaged DNA as the first cell does.