CHAPTER 9 CELL GROWTH AND DIVISION The Cell
- Slides: 11
CHAPTER 9 CELL GROWTH AND DIVISION
The Cell Cycle The cell cycle is the series of events that cells go through as they grow and divide.
9 -1 Cell Growth Two reasons why cells divide instead of continuing to grow; 1. The larger a cell becomes the more demands the cell places on its DNA. 2. The cell has more trouble moving nutrients and waste across the cell membrane.
DNA “overload” When a cell is small, the information stored in the DNA is able to meet all of the cells needs. As a cell increases in size, it usually does not make extra copies of DNA. If a cell were to grow without limits an “information crisis” would occur. Example: small town library with more and more people
Exchanging Material The rate at which the exchange of food, O 2, H 2 O enter the cell and waste leaves the cell through the cell membrane depends on the surface area. The rate at which food and O 2 are used up and the waste products are produced depends on the cell’s volume. This is the reason why a cell must divide.
Ratio of Surface Area (SA) to Volume. SA= 1 cm x 6(faces) = 6 cm ² (squared) Volume = 1 cm x 1 cm = 1 cm³ (cubed) Ratio 6: 1 SA=2 cm x 6 = 24 cm² Vol=2 cm x 2 cm = 8 cm³ Ratio 3: 1 As cells become larger, its volume increases faster than its surface area.
Ratio of Surface Area to Volume
Ways cell division solves problem of cell growth Cell division provides each daughter cell with its own copy of DNA. Cell division increases the surface area of the original cell. Cell division reduces the original cell’s volume.
