Download Compare the size of these organisms

Aim: Why do cells need to divide?
Compare the size of these organisms
Vs.
Vs.
Do these organisms have different
size cells?
No, the cells of a large
organism are the same
size of a small organism.
How do organisms
get so big? Increase number of Cells
Why do cells divide rather
than grow in size?
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1. DNA “Overload”
DNA Library
Small Town
City
The larger the cell, the greater the
demands on the DNA library.
Eventually, the cell’s DNA would no
longer be able to serve the increasing
needs of the growing cell.
2. Exchange of Materials
Depends on:
• Surface Area of Cell
• Volume of Cell
What part of the cell is responsible for
the exchange of materials in and out of
the cell?
Cell Membrane
The rate at which particles are able to
move across the cell membrane depends
on the SURFACE AREA of the cell.
Surface area
Several small particles have a larger
surface area than ONE large particle.
?
SA
Rate of Exchange
A)The greater amount of the cell surface
exposed to the environment, the more
material that can move in or out.
Compare: Surface Area to Volume
B)Less VOLUME in a cell allows materials
to be transported through out the cell
more easily.
C)Cells with a greater surface area to
volume ratio is more effective for the cell
to exchange material in and out of the cell.
What is Cell Division?
The process by which a cell divides into 2
new daughter cells.
What happens to the
chromosomes before a cell
divides? The chromosomes
Size?
need to be replicated
before a cell divides.
Why is important to copy (replicate) all the
DNA in a cell before it divides?
Chromosomes
What are chromosomes
made up of? DNA and
Chromosome
Protein
Centromere
The
chromosomes
are replicated.
Forming two
Chromatids
chromatids.
Replication 2 Chromatids
Chromosome
+ Centromere
When do cells divide?
Repair
Organism Growth
What tissues in our body need
to undergo a lot of cell division?
Skin
Why?
Stomach
Respiratory
The cells of these
tissues are
Bone
constantly growing or
repairing themselves.
Cell Cycle
1. G1 Phase- Cells increase in
size and synthesize new
proteins and organelles.
2. S Phase- DNA
(chromosomes) are
replicated.
3. G2 Phase- Many of the
molecules and organelles for
cell division are produced.
4. M Phase- the cell undergoes
cell division.
Does anyone know what the “M” stands for? Mitosis
Chromosomes
Mitosis Images
Spindle Fibers
Mitosis is the process that divides the cell’s nucleus into two,
each with a complete set of genetic material from the parent cell.