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Cells
are the smallest living parts of any living thing. Cells have
the same needs as any organism and carry out many of the same
activities. Cells contain smaller parts, each with a specialized job. |
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Cells and Their
Functions |
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Of all your body
parts, the smallest part that is considered
alive is a cell. Cells are the basic building
blocks that make up all living things. The |
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tiniest organisms are only single cells. Multicellular
organisms, on the other hand,
have many cells, maybe trillions. Most cells
are too tiny to be seen by the eye alone. A
single drop of blood would hold millions of
red blood cells like the ones pictured here.
You definitely need a microscope to see
them. |
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Cells
in most living things have the same
needs for survival as you do. In other words,
cells do many of the things you do each day
to stay alive. Cells must take in food and get
rid of wastes. Materials in food are used by
the cell to grow and to repair wounds. While
very few cells move around, all cells have parts that
move inside them. Cells sense and
respond to changes in their surroundings.
They often communicate and cooperate with
other cells. |
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This
red blood cell
is magnified about
3,000 times. |
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All cells
need to get energy. Most cells get energy through
cellular respiration. Cellular respiration is the taking in of
oxygen and food, such as sugar, in order to get energy. In this
process, carbon dioxide and water are produced. Different cells
need different amounts of energy for all the things that they do
to survive, including growing, moving, and dividing to
make new cells. |
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| 1. |
What is the most basic unit of living things? |
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| 2. |
Draw Conclusions Suppose
you saw a small organism
move across your desk. Would you infer that this organism
was multicellular or a single cell? |
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