1. Cell Growth and Division
Chapter 10

2. Limits to Cell Size Cells grow as the organism grows.
However cells only grow to a certain extent then divide. Why?
- The larger the cell the more demands on its dna
- a large cell has more trouble moving food in and waste out
Do you remember what the largest cell is?

3. Demands on DNA and exchanging materials
As a cell grows the DNA (deoxyribose Nucleic Acid) stays the same size
- DNA can meet all the cells needs when it is small, but if it becomes too big the cell’s DNA could not keep up with the information the cell needs.
As a cell grows it needs to move more nutrients in and more waste out
- the ratio of the surface area of the cell membrane to volume of the cell changes.
- This difference means the cell has more trouble moving nutrients in and waste out.
Can you think of an analogy to demonstrate the limits on the size of a cell?

4. Cell Division and Reproduction
Cell division Is the process by which a cell divides into two new daughter cells.
How does cell division solve the two limits on cell size?
Types of reproduction:
- asexual reproduction, e.g. Hydras (multicellular organisms that Undergo “budding”) - Sexual Reproduction, some unicellular organisms surprisingly

5. Advantages and Disadvantages
Asexual Reproduction
Sexual Reproduction
Advantages:
Quick
Genetically identical offspring
Disadvantages:
Lack of genetic diversity
Why does this matter in terms of evolution?
Advantages:
Genetically different offspring
Disadvantages:
Slower

6. Chromosomes
Prokaryotic chromosomes are free floating in the cytoplasm in the shape of a circle
Eukaryotic chromosomes are made up of DNA and found in the nucleus
- Humans have 46 chromosomes

7. Organization of genetic material

10. The cell cycle Prokaryotic cells Eukaryotic cells
Asexual reproduction in unicellular organisms called binary fission:
- Cell growth
- Dna replicates
- Cell membrane indents
- cell divides
4 phases:
- G1 (interphase)
- S (interphase)
- G2 (interphase)
- M (cell division):
~Mitosis
~Cytokinesis

11. 4 Phases of the Eukaryotic cell cycle
G1 (interphase) – increase in size and produces new proteins and organelles
S (interphase) – New dna synthesized/chromosomes replicated
G2 (interphase) – organelles and molecules needed for division are produced
M (cell division):
~Mitosis – (Prophase, metaphase, anaphase, telophase) Nucleus divides
~Cytokinesis – cytoplasm divides

12. Cell division Mitosis Cytokinesis
Prophase – Dna Condenses, nuclear envelope breaks down, Spindle forms
Metaphase – Chromosomes line up in center of cell and spindle fibers connect to the centromere
Anaphase – Centromeres split and sister chromatids separate and move to opposite sides of the cell
Telophase – chromosomes unwind into chromatin, nuclear envelopes reform, and spindle breaks down
Cytokinesis
Animal cells – cell membrane is pulled toward
the center of the cell and pinches to form
two identical cells
Plant cells – cell plate forms and develops into new cell
membranes and a cell wall forms between the two
new membranes to form the two new cells