2. Objectives:
Understand why cell growth can cause problems for a cell.
Understand why cell division solves the problems of cell growth.
Understand what happens in the phases of mitosis.
Understand how the cell cycle is regulated and what goes wrong if it is
not.
3. Cell Theory
1. All organisms (living things) are composed of
one or more cells.
2. Cells are the smallest living things.
3. New cells are produced from existing cells.
4. Cells Review:
What are some important organelles in the cell? What is their function?
7. Cell Size Limitations
Ratio of surface area to volume
Surface area is the area covered by the cell
membrane.
Volume is the space taken up by the inner contents
of the cell
Cells with a higher surface area to volume ratio can
sustain themselves for easily.
9. Ratio of Surface Area to Volume
1. Smaller cells can transport nutrients and wastes more
easily.
Diffusion is inefficient over longer distances
Cytoskeleton is less efficient when cells are larger
2. Cellular communication with DNA is more efficient in
smaller cells.
The larger a cell becomes, the more demands the cell
places on DNA.
10. Cell Cycle
Stage Description
Number
of Cells
Interphase
The cell grows in size, performs normal
functions, and copies its DNA. one cell
Mitosis
The cell nucleus divides, and the
chromosomes separate into the two
nuclei.
one cell
Cytokinesis
The cytoplasm of the cell divides,
forming two daughter cells.
two cells
11. Speed of Cell Division
The time it takes for a cell to complete the cell
cycle depends on the type of cell.
A typical animal cell takes 12-24 hours
Some cells take 8 minutes
Other cells can take as long as a year
13. Chromosomes
Carries the genetic information that is passed on from
one generation of cells to the next.
Made up of DNA
Every organism has a specific number of chromosomes
Human cells have 46 chromosomes
Fruit flies have 8 chromosomes
Carrot cells have 18 chromosomes
14. Chromatid
Before cell division, each chromosome makes a copy.
Chromatid
Identical pair of chromosomes
Identical “sisters”
Centromere
15. Chromosome Terminology
Diploid – have two of each chromosome (di = two),
or one full set
Haploid – have half (hap = half) a chromosome set,
or one from each pair
16. Mitosis
A cell nucleus divides to eventually produce two
new cells.
A cell is dividing by mitosis if:
1. Results in two daughter cells.
2. Daughter cells are diploid.
3. Occurs in somatic cells.
18. 1. Prophase (longest phase)
Chromatin organizes into
chromosomes
Centrioles separate to form a spindle.
Nuclear membrane breaks down
19. 2. Metaphase
Chromosomes connect to
spindle fibers at its centromere
Chromosomes line up across
the center of the cell
20. 3. Anaphase
Sister chromatids separate into
individual chromosomes
Chromosomes are moved apart
21. 4. Telophase
Chromosomes gather at opposite ends
of the cell
Nuclear membrane re-forms
Nucleolus reappears
22. Cytokinesis
Cytoplasm pinches in half.
Each daughter cell has an identical set of
chromosomes.
Plant cell: cell plate forms to divide daughter cells
23.
24. Cell Growth
Most cells will continue to grow and divide
until they come into contact with other cells.
Different types of proteins have been found
to help regulate the timing of the cell cycle.
Some are inside the cell and some are outside
25. Uncontrolled Cell Growth
Cancer cells do NOT respond to the signals
that regulate the growth of most cells.
Therefore, they divide uncontrollably and form
masses of cells called tumors.
This can damage surrounding tissues
Cancer cells break off the tumor and can
spread throughout the body.