1. The Cell Theory, Cell Growth, and Cell Division

2. I. The Cell Theory: A. All living things are made of cells.
B. Cells are the basic unit of life.
C. All cells come from preexisting cells.

3. *** Characteristic of Life: Growth and Development

4. II. Cell Growth
Is growth due to cells becoming larger and larger or is it due to more cells being produced?
Answer: MORE CELLS

5. B. Human baby cells are no smaller than adult cells.

6. C. Limits of Cell Growth
1. Food and waste enter and exit through the cell membrane.

7. Speed of this movement is controlled by surface area to volume ratio.
The greater the surface area to volume ratio (SA/V) the faster substances can move in and out.
In general, the smaller the cell the bigger the SA/V
SM. CELL= BIG SA/V= MORE EFFICIENT

8. Within which of these cells would nutrients get to the center fastest?

9. Another factor associated with cell growth is DNA and RNA.
Larger cells use more proteins, which require more mRNA.
The cell only has a limited amount of mRNA.

10. 3. To solve these problems, the cell divides.

11. D. Rates of Cell growth (cell division).
Cells can divide at unbelievable rates, some every 30 minutes.
Rapid growth cannot usually continue for long.

12. E. Controls on Cell Growth
Some cells rarely divide such as heart and nerve cells.
Others such as skin and digestive cells divide frequently.
Normal cells sense when they are touching other cells.

13. Control of cell growth can be turned on and off.
Space, nutrients, light, etc… may also affect cell growth.

14. F. Uncontrolled Cell Growth: A major problem in multi-cellular organisms.
Cells that have lost their growth control are called cancer!!
They do not seem to sense when they come into contact with other cells and will grow until all nutrients are used.

15. Cancer
3. Cancer cells not only divide uncontrollably, they also divide in unusual ways.
Inside Cancer

16. III. Cellular Division
Mitosis and Cytokinesis 1. Mitosis: The first stage in cellular division.
**Process in which the nucleus of the cell is divided into two nuclei, each with the same number and kinds of chromosomes as the parent cell.

17. 2. Cytokinesis: process by which the cytoplasm divides, forming two distinct cells.

18. B. Why is cell division needed?
Growth (fertilized egg to adult)
Repair, replacement (wounds)
a. Bone
b. Skin, weeks
c. RBC’s, 10 million/second
3. Does NOT occur in nerve and muscle cells (EX Heart cells).

19. C. Chromosomes
1. Meaning: “colored bodies”-only can be seen in mitosis. **not normally visible, but will pick up the color of dye.

20. 2. Structures that contain the genetic info
2. Structures that contain the genetic info. (DNA) that is passed on from one generation to the next.

21. 3. The cells of every organism contains a specific number of chromosomes. Ex. Human cells contain 46 chromosomes. 4. Composition: Made up of DNA and proteins.

22. 5. Structure of a Double Chromosome:
Contains two single chromosomes.
Centromere: Each pair of single chromosomes is attached at this area. (Usually located near the center of the chromosome.)
Each chromosome entering mitosis is actually a double chromosome.

23. D. The Cell Cycle: Growth Preparation for division
Divides to form two daughter cells
Daughter cells begin the cycle again.

24. Cell Cycle

25. G1 - 1st period of growth for a cell during interphase.
G0 – some cells will reach a point where they will no longer divide. **EX. Nerve cells—most of them Muscle cells (Ex. Heart cells)

26. 3. S – DNA replication occurs in preparation for division.
4. G2 – 2nd period of growth *Replication of other organelles

27. 5. M – Mitosis a. Prophase, Metaphase,
Anaphase, Telophase b. The NUCLEUS divides.
6. C -Cytokinesis- division of the cytoplasm

28.   E. Interphase:
the chromosomes of the cell are tangled in the nucleus and look like string.
Chromosome number doubles.
Occurs BEFORE mitosis can occur.

29. F. MITOSIS (A closer look):
Normal nuclear division that produces 2 identical nuclei that are DIPLOID (a cell that contains a double set of chromosomes—one from each parent).

30. 1. Prophase: This stage shows the destruction of the nucleus.
Chromosomes become thick and darken.  

31. 2. Metaphase: chromosomes line up in the middle of the cell.

32. 3. Anaphase:
The chromosomes begin to pull apart and the nucleus begins to separate.

33. 4. Telophase: Two new nuclei form.

34. Mitosis and Cytokinesis

35. IPMAT  
*This occurs in body cells, like skin, in order to repair wounds and in all other growing cells.
*This does NOT occur in sex cells.
P M A T

36. G. CYTOKINESIS: As a result of telophase, the cell has 2 nuclei.
Thus, the cytoplasm must also divide. Cytokinesis results in two individual cells.

37. Plant Animation
Animal Mitosis
Cells alive
The Cell Cycle
The Stages of Mitosis

38. Can a Cell Divide Forever?
Normal Cells – NO
Telomeres, buffer zones at the tips of each chromosome, get shorter with each division
Cells die when telomeres are gone
EX: Aging effects are due to dead cells that can no longer be replaced

39. Can a Cell Divide Forever?
Cancer Cells – YES
Telomerase is ON
Enzyme that repairs telomeres after each division
Embryonic Stem Cells – YES
- The Fountain of Youth lies in harnessing the anti-aging powers of telomerase without the risks associated with cancer. This is NO EASY TASK…