Mitosis

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.

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.

Cells Review:

What are some important organelles in the cell? What is their function?

Atom

Molecule

Macromolecule

Organelle

Cell

Tissue

Organ

Organ System

Organism

Cellular Organization

Needs of a Cell?

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.

Surface Area to Volume Ratio

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.

Cell Cycle

Stage DescriptionNumber of Cells

InterphaseThe 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

CytokinesisThe cytoplasm of the cell divides, forming two daughter cells.

two cells

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

Cell Cycle

Cell Growth

DNA

replication

Preparation

for mitosis

Mitosis

and

Cytokinesis

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

Chromatid

Before cell division, each chromosome makes a copy.

Chromatid

Identical pair of chromosomes

Identical “sisters”

Centromere

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

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.

Mitosis Phases

1. Prophase

2. Metaphase

3. Anaphase

4. Telophase

1. Prophase (longest phase)

Chromatin organizes into

chromosomes

Centrioles separate to form a spindle.

Nuclear membrane breaks down

2. Metaphase

Chromosomes connect to

spindle fibers at its centromere

Chromosomes line up across

the center of the cell

3. Anaphase

Sister chromatids separate into

individual chromosomes

Chromosomes are moved apart

4. Telophase

Chromosomes gather at opposite ends

of the cell

Nuclear membrane re-forms

Nucleolus reappears

Cytokinesis

Cytoplasm pinches in half.

Each daughter cell has an identical set of

chromosomes.

Plant cell: cell plate forms to divide daughter cells

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

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.