1. Cell Growth and Divison
Chapter 10

2. 10.1 Cell growth, division, and reproduction
Limits to Cell Size
We learned in Chapter 7, that small cells are more
efficient than large cells.
•The larger a cell becomes,
• the more demands the cell places on its DNA
• the less efficient in moving nutrients and waste materials
across the cell membrane.

3. Cells need a high sa/v ratio

4. Cell Division
An adult produces 25 million new cells per second.
Why do cells divide?
1.
2.
3.
Asexual reproduction
Unicellular organism developing into a multicellular organism
(growth)
Renewal and Repair of damaged cells
•
In each situation DNA must be present in each new
cell.
•
When a cell divides the DNA is copied and distributed
so that each cell ends up with an exact copy of the
DNA.

5. Asexual Reproduction
• Prokaryotic cells reproduce by binary fission
• Produces identical offspring where a parent passes exact copies
of its DNA to its offspring.
parent cell
DNA
duplicates
cell begins
to divide
daughter
cells

6. Asexual reproduction
Eukaryotic organisms can also reproduce asexually.
• Budding forms a new organism from a small projection
growing on the surface of the parent.
• Fragmentation is the splitting of the parent into
pieces that each grow into a new organism.
Hydra
bud
Yeast

7. Sexual reproduction
• Involves the fusion of two parent cells
• Offspring inherit some information from each parent

8. 10.2 THE PROCESS OF CELL DIVISION
CHROMOSOMES – condensed chromatin
•A single molecule of DNA has thousands of genes
•DNA is arranged into chromosomes
• Prokaryotes – single circular chromosome in cytoplasm
• Eukaryotes – multiple chromosomes are located in the nucleus

9. Eukaryotic Chromosomes
• Each chromosome is made up of 2 sister chromatids
• The sister chromatids are attached at a centromere
chromatid
centromere
Condensed, duplicated chromosome

10. Chromosomes in Sexual Reproduction
• Somatic Cell – normal body cell, not a sperm or egg cell.
• Diploid
• In a normal human contains 46 chromosomes
• Gamete – sex cell, sperm or egg
• Haploid
• In a normal human contains 23 chromosomes
• Why?
• When two haploid gametes fuse in fertilization, the
result is a diploid zygote (the first cell of a new
individual).

11. The Cell Cycle
The cell cycle is a regular pattern of growth, DNA
replication, and cell division.

12. Stages of the Cell Cycle
• Interphase
• G1: cell growth and normal
functions
• S (synthesis): copies DNA
• G2: additional growth and
preparation for division
• Cell Division (M phase)
• Mitosis
• division of the cell nucleus
• Cytokinesis
• division of the cell cytoplasm

13. interphase
Before cell division can begin the cell will go
through interphase.
Parent cell in Interphase
centrioles
spindle fibers
centrosome
nucleus with
DNA

14. Steps of Mitosis
• Step I: Prophase
• chromosomes condense
• Spindle fibers form from centrioles.
• Nucleolus disappears and the nuclear envelope breaks down

15. • Step 2: Metaphase
• Centromeres of chromosomes line up in the middle of the cell
• Spindles attach to centromeres

16. • Step 3: Anaphase
• sister chromatids separate and move along the spindle fibers to
opposite sides of the cell

17. • Step 4: Telophase
 the new nuclear envelopes form and chromosomes begin
to uncoil into chromatin
 Mitosis is complete! (cell division still has one more step)

18. Cytokinesis
• In animal cells, the membrane pinches closed.

19. • In plant cells, a cell plate forms.
• After cytokinesis in all cells, each new cell begins
interphase.
• Cells Alive Animation

21. Review Questions
Compare asexual and sexual reproduction.
How does cytokinesis compare in plant and animal
cells?
Describe the relationship between the following
terms: chromatin, chromosomes, chromatid, and
centromere.
Mitosis song

22. 10.3 regulating the Cell Cycle
• One of the most important internal factors that
regulate the cell cycle are:
• Cyclins (regulatory proteins)

23. External Factor
• Normal cells stop
dividing when they
touch each other.

24. Cancer cells
• If one of these factors is mutated regulation of
growth and division can be disrupted.
• Cancer cells do not respond normally to the
bodys control mechanisms.
• As a result they divide uncontrollably and form a mass
of cells called a tumor.
Metastasis Animation

25. 10.4 Cell Differentiation
• As a zygote grows into stem
cells, and then an embryo, the
cells become specialized
through the process of
differentiation.
• Differentiated cells are specialized
to perform certain jobs.
• Example: nerve cells, muscle cell,
blood cell, skin cell

26. Stem Cell Research
• Embryonic stem cells
vs. adult stem cells
• Benefits
• Fix damaged cells
• Treat devastating
diseases (leukemia,
diabetes)
• Issues
• Ethics
• Expensive