THE IMPORTANCE OF CELL DIVISION

Science 9

Where do cells come from?

New cells come from pre-existing cells through the process of cell division

This is how dead and damaged cells are replaced in the human body

Functions of Cell Division – Healing and Tissue Repair Every second of your life, millions of cells

are becoming damaged or dying in the human body

They constantly need replacing Some of the activities we undergo

remove these cells such as washing, getting dressed, rubbing hands on your clothes, etc.

Functions of Cell Division - Growth As the number of cells increase in a living

thing, so does its size Human growth begins with the division of a

fertilized egg cell All cells are approximately the same size They need to divide because if they

continued to grow, they would not be able to acquire all the materials they would need to survive

Also, the distance the nucleus is from all other parts of the cell must be kept at a minimum so that messages can be translated quickly and efficiently

Functions of Cell Division - Reproduction Cell division promotes life Cell division in unicellular organisms like

bacteria produces two more organisms Cell division is also critical for

reproducing multicellular organisms

Cell Division

There are approximately 100 trillion cells in the human body

However, it began as a single fertilized egg

It divided into two cells and so on until you were produced

The Cell Cycle – step 1

There are two phases of cell division: when it is dividing and when it is not

The actual phase where it divides is small compared to the other events that take place within the cell

The stages between cell divisions is called interphase

During this time, cells take in nutrients, which are important for energy, growth, and repair of the cell

The Cell Cycle – step 2

A phase of rapid growth occurs

This is a period of interphase because cell division is not occurring

The Cell Cycle – step 3

The cell prepares for division by duplicating its chromosomes within the nucleus (replication)

This must occur before cell division

The chromosomes contain all the important information needed for the cell to survive

This is also a period of interphase

The Cell Cycle – step 4

Another period of growth and preparation for cell division occurs

Again, this is a period of interphase

Mitosis

Most cells divide the same way

All cells divide into two cells – a mother cell produces two daughter cells

The division of information in the nucleus and the sharing of cytoplasm by moving to opposite ends of the cell is called mitosis

Cytokinesis

Cell division continues with the separation of cytoplasm and its contents into equal parts

This begins before mitosis is complete Half of the cytoplasm, containing half of

the organelles, goes to each daughter cell

This process differs between plants and animals

Cytokinesis – Plants and Animals In plants, a cell wall forms along the middle of

the cell, creating two new cells

In animals, the cell membrane pinches together in the middle, separating the cytoplasm into two equal parts

Both daughter cells grow and develop complete organelles during interphase

They will also make a copy of genetic material

The Phases of Mitosis

Interphase cell grows and duplicates genetic material

Prophase Individual chromosomes (two strands of information)

becomes visible Metaphase

Double-stranded chromosomes line up in the middle of the cell

Anaphase Each chromosome splits and moves to opposite ends of

the cell Telophase

A nuclear membrane forms around each strand; cytokinesis begins

Interphase Cell continues to grow and duplicates its genetic material

Videos

The Cellhttp://www.youtube.com/watch?v=X6N82No4Nz8

Mitosishttp://www.youtube.com/watch?v=L0k-enzoeOM