Download What Is a Cell? - Avery County Schools

Name
Date
What Is a Cell?
By Cindy Grigg
Cells are the building blocks of all living things. A cell is the
smallest part of a living thing that carries out actions that keep the thing
alive. Some living things are made of only one cell-they are
unicellular. People are multicellular. The human body is made of
more than one hundred trillion cells!
Cells are usually placed into two groups. There are cells with a
nucleus and cells without. Cells without a nucleus are very simple cells.
Bacteria cells lack a nucleus. Plants and animals are made of cells that
do have a nucleus.
All cells are filled with cytoplasm. This jelly-like fluid has many
chemicals in it that help the cell stay alive. Cells are also classified as
either plant or animal cells.
Structures inside the cell carry out the cell's functions. These structures are called organelles.
Organelle means "little organ." Organs in your body like your heart and lungs carry out actions
that keep you alive. Organelles in cells have jobs, too. Plant and animal cells have organelles
that are similar. Each organelle in both plant and animal cells is enclosed by a membrane.
Plant cells have two different organelles that animal cells do not. Plant cells have a rigid cell
wall and chloroplasts. Chloroplasts allow plants to make their own food.
Most cells have a nucleus. (One cell that doesn't is the red blood cell.) The nucleus is called
the cell's command center. It controls the cell's actions. It contains the DNA. DNA is the genetic
material that lets cells make more of themselves and pass on their traits to new cells.
Every cell has a cell membrane. The membrane holds the parts of the cell together. It keeps
the cytoplasm inside. It provides a barrier between the cell and its surroundings.
Mitochondria (might oh KAHN dree uh) are the organelles in a cell that convert food into
energy. Vacuoles are places to store supplies like water until the cell needs them. Wastes and
food can be stored, too. There are many other organelles. Each has a job to do.
All living things are made of one or more cells. Plant and animal cells are alike in many
ways. All cells have jobs to do that support life.
Name
Date
What Is a Cell?
Questions
1. The smallest part of a living thing that carries out actions that keep the thing alive is ______.
A. an atom
B. an organ
C. a molecule
D. a cell
2. The jelly-like fluid inside a cell is the ______.
A. cytoplasm
B. cell membrane
C. chloroplast
D. organelle
3. Plant cells and animal cells have many of the same organelles.
A. true
B. false
4. Organelles are ______.
A. called little organs
B. parts inside a cell that carry out actions that keep the cell alive
C. parts of a cell like the chloroplast and the vacuole
D. all of the above
5. What is DNA?
6. Which of these is a fact?
A. Plant cells have some organelles that animal cells do not.
B. People have organelles like the heart and lungs.
C. Animal cells have some organelles that plant cells do not.
D. Only animal cells have a cell membrane.
7. What does "multicellular" mean?
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Date
8. What does the prefix mean in the word "unicellular"? Do you know any other words with
that prefix? What does that word mean?