1. Chapter 10
Cell Growth & Division

2. Cell Growth, Division & Reproduction

3. Why does a cell divide? If the cell is too large…
its DNA cannot meet all of the cell’s needs
Ex: library for a growing town
nutrients and wastes cannot be moved across the cell membrane well  surface area : volume ratio

4. Surface area : Volume
rate of exchange over the cell membrane depends on its’ surface area
rate at which food and oxygen are used and waste is produces depends on its’ volume
as a cell grows larger, its’ surface area : volume ratio gets SMALLER  waste will be
produced faster (bigger
volume), but it can’t be
removed as quickly (smaller
surface area)
Sooo… The cell must divide!

5. Cell division
process by which a cell divides, forming two daughter cells
before dividing, each cell duplicates its DNA so that each daughter cell gets one copy

6. The Process of Cell Division

7. Chromosomes Made of DNA & proteins. Carry the cells genetic info.
Every organism has a specific number of chromosomes
Bacteria = 1 circular chromosome in the cytoplasm
Humans = 46 chromosomes

8. Chromosomes (continued)
In eukaryotes, they are normally spread throughout the nucleus & aren’t visible (called chromatin).
Before cell division, each chromosome is replicated, forming 2 chromatids,
attached by a centromere.

9. The Prokaryotic Cell Cycle = Binary Fission

10. The Eukaryotic Cell Cycle
During the cell cycle, the cell grows, prepares for division, and divides into 2 daughter cells, each of which begins the cycle again.
Phases:
G1: cell growth
S: DNA replication Interphase
G2: preparation for mitosis
M: mitosis (division of the
cell nucleus) & cytokinesis

11. Mitosis
Interphase
Prophase
Metaphase
Anaphase
Telophase/Cytokinesis

12. Interphase Chromosomes are copied.
Chromosomes and copies appear as chromatin.
Nucleolus and
nuclear envelope are visible.
(Nucleolus makes ribosomes.)

13. Prophase Chromosomes become visible.
Centrioles appear and move to opposite ends of cell.
Spindle fibers form.
Nuclear envelope
disappears.

14. Metaphase Chromosomes line up across center of cell.
Spindle fibers attach to centromeres.

15. Anaphase
Sister chromatids are pulled apart.

16. Telophase/Cytokinesis
Chromosomes lose shape, appearing as chromatin.
Nuclear membranes reform.
Cytoplasm pinches in half (cytokinesis).
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17. Regulating the Cell Cycle

18. How long does cell division take?
Some cells (ex: muscle & nerve cells) do not divide at all once developed, while others (ex: skin & digestive tract cells) divide every few hours.

19. How is the cell cycle regulated?
Regulatory Proteins regulate the timing of the cell cycle
Both internal & external to the cell.
Most cells will stop growing when they come in contact with other cells.

20. Apoptosis programmed cell death
Cells chromatin shrinks, its cell membrane breaks apart & neighboring cells clean up the remains.
AIDs & Parkinson’s disease can result when apoptosis doesn’t occur as it should.

21. Cancer uncontrolled cell growth
Tumor: mass of cells formed from cancer
May be benign (nonspreading) or malignant (spreads to other tissue).
Lecture 1: min