Download 2—6 Why do cells have different shapes? Cell Size and Shape

2—6 Why do cells have different shapes?
Cell Size and Shape Some organisms are made of only one cell. They are called unicellular. In
unicellular organisms, all of the life processes are carried out by the same cell. Most organisms you are
familiar with have more than one cell. These organisms are called multicellular. The cells of these
organisms are not all the same. They have different sizes and shapes. Different kinds of cells have
different jobs. The shapes of most cells help them do their jobs.
Amoeba An amoeba (uh-MEE-buh) is a unicellular organism that lives in water. These organisms have
the ability to change shape. Amoebas use temporary, fingerlike extensions of the cytoplasm to move
and get food. These extensions are called pseudopods. An amoeba uses its pseudopods to surround
food particles. Then, the pseudopod closes around the food particle and digests it.
Pseudopod of amoeba Red Blood Cells
Nerve Cells
Guard Cells
Nerve Cells Nerve cells store or transfer information. There are different types of nerve cells. The nerve cells in
the brain store information. Other kinds of nerve cells carry messages from one part of the body to another.
These messages are called impulses. Nerve cells that carry information are usually long and very thin. Some
nerve cells are the longest of all the cells in your body.
Guard Cells Two bean-shaped cells called guard cells surround a tiny opening on the outer surface of a plant
leaf. This opening is called a stoma. A stoma lets carbon dioxide into the leaf and releases oxygen and water
into the air. Guard cells control the size of the stoma. When the guard cells swell, the stoma opens. When the
guard cells shrink, the stoma closes.
CHECKING CONCEPTS
1.
Organisms with one cell are
2. Amoebas use
to capture food.
3. The job of a
is to carry oxygen.
4. A
is a tiny opening on the outer surface
of a plant leaf.
5. The
control the size of the stoma.