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Parts of the Cell
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- ATP: Adenosine triphosphate. ATP is the energy-carrying molecule of all cells... more
- Chromosome: long thread-like molecule made of the chemical called DNA (deoxyribonucleic acid) that are held together with special proteins and are visible during cell division... more
- Organelle: "little organ". An internal organ of a cell... more
- Phospholipid: is a special kind of lipid that is made up of two fatty acid chains. These phospholipids are present in the plasma membrane of any cell... more
- Photosynthesis: It is a set of chain reactions that convert light energy into chemical energy. Photosynthesis also produces energy-rich carbohydrates like starch. Photosynthesis occurs in the chloroplast of a plant cell... more
- Tomography: process used to make a tomogram (picture) which is a two-dimensional slice of a three-dimensional object. A computer can then be used to build a three-dimensional image of the object by stacking the tomograms together.
Do all cells look the same?
Cells come in many shapes and sizes. Some cells are covered by a cell wall, other are not, some have slimy coats or elongated structures that push and pull them through their environment. Some cells have a thick layer surrounding their cell. This layer is called the capsule and is found in bacteria cells.
In our body there are many different kinds of cells. We are made up of about 200 different types of cells. Our body also has non- living materials such as hair, finger nails, and the hard part of the bone and teeth. All these materials are made up of dead cells.
Taking a look inside a cell
Have you ever wondered what the inside of a cell looks like? If you think about the rooms in our homes, the inside of any animal or plant cell has many similar room-like structures called organelles.
Both plant and animal cells have many of the same organelles. In some cases, like plant cells, there are more types of organelles than are found in animal cells. All organelles in a cell perform different functions. Here are some names and descriptions of organelles commonly found in cells:
| Plasma membrane- The membrane enclosing a cell is made up of two lipid layers called a "bilipid" membrane. The lipids that are present in the plasma membrane are called "phospholipids." These lipid layers are made up of a number of fatty acid building blocks. The fatty acid that makes up this membrane has two different parts to it- a small water loving head- hydrophilic head. Hydro stands for water and philic means liking or loving. The other part of this fatty acid is a long water-repelling or water hating tail. This tail is hydrophobic- Hydro stands for water and phobic
means fear. The plasma membrane is arranged in such a way so that the
tails face each other on the inside and the heads face towards the
outside of the membrane.
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 | Channels/pores- A channel in the cell's plasma membrane. This
channel is made up of certain proteins whose function is to control the
movement of food and water into the cell. These channels are made up
of certain proteins.
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 | Nucleus- The
nucleus is the control center of the cell. It is the largest organelle
in the cell and it contains the DNA of the cell. DNA (Deoxyribonucleic Acid) contains all the information for cells to live, perform their functions and reproduce.
The circles on the surface of the nucleus are the nuclear pores.
These are where ribosomes, and other materials move in and out of the
cell.
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| Endoplasmic reticulum (ER)- It is a network of membranes throughout the cytoplasm of the cell. There are two types of ER. When ribosomes are attached it is called rough ER and smooth ER when there are no ribosomes attached. The rough endoplasmic reticulum is where most protein synthesis
occurs in the cell. The function of the smooth endoplasmic reticulum is
to synthesize lipids in the cell. The smooth ER is also helps in the
detoxification of harmful substances in the cell.
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| Ribosomes- Organelles that help in the synthesis of proteins. Ribosomes are made up of two parts, called subunits.
Both these subunits are necessary for protein synthesis in the cell. When the two units are docked together with a special information unit called messenger RNA, they make proteins. Some ribosomes are found in the cytoplasm, but most are attached to
the endoplasmic reticulum. While attached to the ER, ribosomes make
proteins that the cell needs and also ones to be exported from the cell
for work elsewhere in the body.
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| Golgi complex- It is the organelle in the cell that is responsible for sorting and correctly shipping the proteins produced in the ER. Just like our postal packages which should have a correct shipping address, the proteins produced in the ER, should be correctly sent to their respective address. In the cell, shipping and sorting is done by the Golgi complex. It is a very important step in protein synthesis. If the Golgi complex makes a mistake in shipping the proteins to the right address, certain functions in the cell may stop. This organelle was named after an Italian physician-Camillo Golgi.
He was the first person to describe this organelle in the cell. It is
also the only organelle that is capitalized.
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| Mitochondria- This is the cell’s powerhouse. This organelle packages the energy of the food into ATP molecules. Every type of cell has a different amount of mitochondria.. There
are more mitochondria in cells that have to perform lots of work, for
example- your leg muscle cells, heart muscle cells etc. Other cells
need less energy to do their work and have less mitochondria.
|
 | Chloroplast- The cell organelle in which photosynthesis takes place. In this organelle the light energy of the sun is converted into chemical energy. Chloroplasts are found only in plant cells not animal cells. The chemical energy that is produced by chloroplasts is finally used to make carbohydrates like starch, that get stored in the plant. Chloroplasts contain tiny pigments called chlorophylls.
Chlorophylls are responsible for trapping the light energy from the sun.
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| Vesicles- This term literally means "small vessel". This organelle helps store and transport products produced by the cell. The vesicles are the transport and delivery vehicles like our mail
and Federal Express trucks. Some vesicles deliver materials to parts of
the cell and others transport materials outside the cell in a process
called exocytosis.
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 | Vacuole- Plant cells have what looks like a very large empty space in the middle. This space is called the vacuole. Don't be fooled, the vacuole contains large amounts of water and
stores other important materials such as sugars, ions and pigments.
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| Cytoplasm- A term for all the contents of a cell other than the nucleus. Even though the cartoon drawings do not look like it, the cytoplasm contains mostly water. Some fun facts about water and the human body:
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 | Cell wall and Plasmodesmata- In addition to cell membranes, plants have cell walls. Cell walls provide protection and support for plants. Unlike cell membranes materials cannot get through cell walls. This would be a problem for plant cells if not for special openings called plasmodesmata. These openings are used to communicate and transport materials
between plant cells because the cell membranes are able touch and
therefore exchange needed materials.
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 | Peroxisomes- These collect and safely break down chemicals that are toxic to the cell.
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 | Centrioles- These are found only in animal cells and come into action when the cells divide, helping with the organization of chromosomes.
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 | Lysosomes- Created by the Golgi apparatus, these help break down large molecules into smaller pieces that the cell can use.
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 | Cytoskeleton- Made up of filaments and tubules, it helps shape and support the cell. It also helps move things move around in the cell. For artistic purposes, the cytoskeleton is shown in just one place
when in reality it is found throughout the entire cell.
|
Inside
the nucleus is another organelle called the nucleolus. The
nucleolus is responsible for making ribosomes.
They get their names from their size.
One unit is larger than the other so they are called large and
small subunits.
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