Download Division of plant and animal cells

National 4 and 5- Cell Division
Investigating Cell Division
Cell division is the way in which an organism increases its number of cells.
division means different things for unicellular and multicellular organisms:
Cell
Unicellular - Cell division results in the production of a new organism.
Multicellular - Cell division results in growth of the organism and repair damaged
parts.
Division of plant and animal cells
Cell division, and all other activities, of both plant and animal cells are controlled
by the nucleus. The nucleus contains thin, threadlike structures called
chromosomes that carry all the cells information:
Chromatid
Centromere
Chromatid
After cell division, the two cells produced contain exactly the same number
of chromosomes and therefore all of the cells information. The process by
which this occurs is called mitosis.
1
Mitosis
1. Chromosomes coil up and become shorter and thicker.
Then can now be
stained and viewed under a microscope.
2. Chromosomes line up along the equator (centre) of the cell and a spindle
forms, attaching to the centromere of each chromosome.
3. The centromere splits and each chromatid is pulled to the opposite poles
(ends) of the cell.
4. A nuclear membrane forms around each clump of chromatids and the
cytoplasm begins to divide.
5. The cytoplasm divides completely and the separated chromatids are now
known as chromosomes.
6. Each cell grows, and while this is happening the chromosomes uncoil and
replicate to produce two identical chromatids. Once the chromosomes have
uncoiled it is no longer possible to view them under a microscope.
2
Chromosome Complement
Chromosomes contain the information that determines the characteristics of
every cell in an organism. Consequently, chromosomes determine what
characteristics an organism possesses and what characteristics it does not.
Every species of plant and animal has a characteristic number of chromosomes
in each of its cells. This number is known as the chromosome complement. In
order for an organism to have all the characteristics of it’s species it must have
all of the chromosomes of that species (a complete complement of
chromosomes) in its cells. Mitosis ensures that all of the chromosomes of a cell
are passed on when that cell divides.
Diploid cells have two matching sets of chromosome which are replicated during
mitosis.
Cancer
Cancer is an example of uncontrolled cell division.
Cell culture
(Covered in more detail in therapeutic uses of cells later)
Cell production by cell culture requires aseptic technique and appropriate
medium. Factors such and oxygen concentration, temperature and pH can
affect the growth of cells.
In any work using microorganisms a great deal of care has to be taken. This is to
ensure that any unwanted microorganisms are not grown and released to
surroundings.
In the lab:
1.
2.
3.
4.
5.
6.
7.
8.
9.
Always wear a lab coat and safety glasses.
Wash your hands before starting.
Wipe work surfaces with disinfectant.
Use only sterilised equipment.
Dispose of materials safely.
Wipe surfaces again.
Wash hands when finished.
Do not eat or drink.
Never open dishes containing microbes.
3
These precautions must also be taken in biotechnological processes to avoid
contamination.
Check point A2
Level 4 E&O
By researching cell division, I can explain its
role in growth and repair and can discuss how
some cell can be used therapeutically 4.13 a
Nat 4
cell division and its role in growth and repair
Cell division is essential to allow organism to
grow and repair damaged parts. During cell
division, the parent cell divides to produce two
identical cells, which contain the same number
of chromosomes in the nuclei as the parent
cell. Cancer is uncontrolled cell division.
Nat 5
Producing new cells
a. Maintenance of diploid chromosome
complement by mitosis.
b. Sequence of events of mitosis, including the
terms chromatids, equator and spindle fibres.
c. Cell production by cell culture requires
aseptic techniques, an appropriate medium and
the control of other factors.
d. Mitosis is required for growth and repair
4