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What is a cell?
A cell is the very smallest unit of living
matter. All living things including plants
and animals are made up of cells.
What is a cell made
of?
Cells are made of atoms, which
are the smallest units of matter.
How many different
types of cells are
there?
There are many different kinds
of cells. The two kinds you may
already be familiar with are
animal and plant cells.
What makes plant cells
different from animal cells?
One main difference is that plant cells
contain chloroplasts which contain
chlorophyll. Another difference is that
plant cells have a rigid cell wall while
animal cells have a flexible cell
membrane.
Is there anything inside an
animal cell?
Cells are tiny, but they
have lots of important
parts inside! These
different parts are
called organelles –
because they are like
our organs but smaller!
What different organelles make up
an animal cell?
One part found in all
cells is the cell
membrane. The cell
membrane surrounds
the cell, holds the other
parts of the cell in place,
and protects the cell.
Inside the membrane, all cells, except for bacterial
cells, contain a nucleus and cytoplasm. The nucleus is
a dark structure located in the middle of the cell. It
controls the cell's activities, and acts like the cell's
brain. Inside the nucleus there is DNA which contains
genetic information.
The cytoplasm is a jelly-like substance inside the cell
where most of the cell's activities take place. It's
made out of water and other chemicals. All cell
parts, except the nucleus, are located in the
cytoplasm
Like all living things, cells die. If you watched a
clock for one minute, about three billion cells in
your body die.
The length of time cells live can vary. For
example, white blood cells only live for thirteen
days, red blood cells live for about one hundred
and twenty days, liver cells live about eighteen
months, and nerve cells can live up to one
hundred years. That is a very big difference!
How do I get new cells when the
old ones die?
Basically, each cell is made
from an already existing cell.
New cells are made through
a process called cell division
or mitosis. One cell turns into
two cells and then each of
those two cells turn into four
cells, etc. Even humans
started life with only one
cell.
How do I get new cells when the
old ones die?
Most of the cells in multi-celled
organisms use mitosis to
reproduce. The animation shows
the basic steps in mitosis which are:
1) At the start of mitosis
chromosomes are in the nucleus.
2) The chromosomes in the nucleus
will then make a copy of
themselves
3) Next the cell divides.
4) Lastly, one set of chromosomes
goes to the new cell and one set
remains in the parent cell.
Organisms like humans are made up of
trillions of cells. There are also one celled
organisms such as euglenas, amoebas, and
bacteria.
If cells are so tiny, how do
scientists study them?
One of the most important tools that
scientists use to study cells is the microscope.
An optical microscope can magnify a cell up
to two hundred thousand times. If an ant
were to be magnified at two hundred
thousand times, it would be more than two
and one half miles long. Scientists also put
dyes in cells to make certain parts look
bright under a microscope.
Do all cells inside me look the
same?
No, different cells have different jobs. Cells
with different jobs can look very different.
All cells start
as stem cells.
Once they are
‘assigned’ a
job, they
change to fit
their purpose.
Blood Cells
Skin Cells
Nerve Cells
Cancer is caused by cells that
don’t duplicate correctly. Cells
in our immune system will try
to kill the bad cells.
Immune Cells
Attack Cancer Cell
Let’s Review
What are some differences between
animal and plant cells?
Plant Cell
Sketch a diagram of a plant and animal cell in
your journal. What are 2 things they have in
common? What are 2 main differences?
Plant Cell