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The Cell
You can’t put me into a cell! I won’t go! Okay, maybe I’m being a bit too
dramatic, but it gives you something to think about. Now that we know
the cell is the basic unit of all living things, we need to explore what is
found in and around the cell and how do they work.
The various parts of the cell are referred to as organelles, which mean
“little organs”. They function very much like our organs. It is important to recognize that the
parts of the cells work together to provide all the functions needed for life. Let us start our
journey on the outside of a cell and work our way to the middle. After that, we will explore the
differences between animal and plant cells.
Cell Membrane
The outer most layer of the cell is called the cell membrane. It functions as the gatekeeper of
the cell allowing only materials the cell needs to survive into the cell while allowing the waste to
pass out of the cell. These processes are done through osmosis and diffusion. Osmosis is when
water passes from an area of more water to an area of less water. If the cell needs water, it will
be allowed to pass through the cell membrane until the amount of water on the inside of the cell
is equal to the amount of water on the outside of the cell. Diffusion is the same as osmosis;
however it is gases moving through the cell membrane.
Cytoplasm
Once we travel through the cell membrane, we enter the cytoplasm. The cytoplasm is a cell
jelly-like substance that fills the inside of the cell and is constantly moving. It provides
protection for the organelles located inside the cell and also allows materials to move around the
cell.
Mitochondrion
Mitochondria, the plural of mitochondrion, are the powerhouses of the cell. Inside these
organelles, respiration occurs. The mitochondria will convert glucose, a simple sugar, and
oxygen into ATP which is a chemical that is stored energy. ATP is what provides the cell with
the energy it needs for living. These organelles look like little jelly beans and float around the
cytoplasm.
Nucleus
Also found inside the cytoplasm is the nucleus. The nucleus is a ball-shaped organelle that is
responsible for regulating all activities inside the cell. In essence, it acts similar to the brain. Do
not think the nucleus can solve world hunger or ponder the meaning of life though. Inside the
nucleus, there are several types other organelles found in the nucleus.
Nuclear Membrane
Just as the cell membrane protects the cell, the nuclear membrane protects the nucleus from
foreign substances by allowing certain materials to pass into or out of the nucleus. The nuclear
membrane is the outer most layer of the nucleus.
Chromosomes
Chromosomes are perhaps the most important organelle found in the cell. The chromosomes are
rod-like organelles found in the nucleus that carry the chemical code to re create and repair the
cell. The chromosomes are literally the blue prints of the cell. They are composed of
deoxyribonucleic acid (DNA) and are tightly wound in the shape of a double helix. A double
helix looks like a ladder that has been twisted. These rods unwind when the cell needs to either
reproduce or produce the proteins called ribosome needed to build a replacement part for the cell.
Nucleolus
This is a really interesting part of the nucleus. Scientists discovered it back in the 1860’s but did
not understand what its function was until recently. This small ball-shaped organelle found
inside the nucleus is responsible for producing smaller bits of protein that will eventually
combine to become ribosome. Remember ribosome is used to build and repair parts of the cell
so the nucleolus is essential for the cell to continue living. Now how do these ribosomes exit the
nucleus and enter the cytoplasm?
Endoplasmic Reticulum
Attached to the nucleus are tubes that travel into the cytoplasm in the cell. These tubes are called
the endoplasmic reticulum and are responsible for delivering the ribosome to the place they are
needed for construction or repair. It the cytoplasm is the bus system of the cell, transporting
large quantities of material around the cell, the endoplasmic reticulum would be like a limousine,
transporting small amounts of material to a specific spot in the cell. Now let’s discuss what’s
being transported.
Ribosomes
Ribosomes are small grain-like proteins that the cell uses for repair or construction. They are
formed from the codes found in the chromosomes and produced in the nucleus. Upon
completion, they travel through the endoplasmic reticulum and are placed where they are needed.
Occasionally, ribosomes can be floating in the cytoplasm.
Organelles Found Mostly in Plant Cells
Remember, plant and animal cells do differ in a few significant ways. A microscope can reveal
these differences clearly and quickly. Let’s explore these differences.
Cell Wall
Found outside of the cell membrane, the cell wall provides a rigid structure for a plant cell.
Constructed of cellulose, this organelle protects the cell from damage and is similar to a skeleton.
Even when the plant is dead, the cell wall will remain. That is what wood is when we chop
down the tree.
Chloroplast
This is probably the biggest difference between plant and animal cells: the chloroplast. Located
in the cytoplasm, the green colored bean-like chloroplasts are where photosynthesis occurs in
the cell. Photosynthesis allows a plant to take carbon dioxide, water and sunlight and transform
them into glucose and oxygen, the food needed for the plant. Pretty tricky! All a plant needs to
make food are just some basic ingredients and the sun! There are a few animals that have
chloroplasts but it is very rare.
Vacuoles
Also located inside the cytoplasm of plants are these large organelles. Vacuoles are basically
just giant storage tanks, holding much needed materials for the cell. Most commonly found in
vacuoles is water. When the vacuole is not full the cell may lose some of its shape. Have you
ever seen a droopy leaf on a plant that hasn’t been watered for a while? Now you know why it
looks the way it does. Rarely, vacuoles can be found in some animal cells.
Organelle Found Mostly in Animal Cells
Lysosomes
The lysosome is a small round organelle located in the cytoplasm and is responsible for the cell’s
digestion. Inside the lysosome, chemicals work to break down food into the basic materials that
the cell needs to sustain life. Lysosomes also act as the clean-up crew for the cell. If an
organelle is no longer working or is not needed it will be digested by the lysosome so that the
materials can be reused by the cell. Talk about recycling!
Now that you have an understanding of what each part is and what it does, take the time to learn
where you may find them inside of the cell. Truly this will be a fascinating journey!
The Cell
Diffusion
Ribosomes
Cell Wall
Mitochondrion
Organelles
Vacuoles
Chromosomes
Osmosis
Lysosomes
Cytoplasm
Endoplasmic Reticulum
Nucleus
Chloroplast
Nucleolus
Nuclear Membrane
Cell membrane