Cell Organelles
All eukaryotic cells have within them a variety of different structures called organelles. Organelles are small and function much like organs function in a large organism. Some organelles are responsible for gathering cell energy, others for controlling cell activities. Plant cells have different organelles than animal cells but also share many also. They all have a large variety of sizes and functions and make life as we know if possible. Click the links in the yellow boxes for more detailed information on each of the organelles. Some links may not be active yet - I'm still writing the site and some of the pages may not be up yet.
Nucleus
The nucleus is one of the most important organelles in a cell. It is often the largest organelle in animal cells, but this is not always the case. Nuclei contain the genetic material called DNA that is responsible for controlling and directing all cell activities. This is a very important organelle given its vital function.
Nucleolus
The nucleolus is a small structure found within the nucleus that functions to produce ribosomes for the cell.
Cytoplasm
The Cytoplasm is the gel-like substance that fills the cell outside the nucleus. All of the cell's organelles are held and located within the cytoplasm. There are many different chemicals, nucleic acids, and other substances that the cell needs can be found there also. It supports the cell and gives it shape.
Cell Membrane
The cell membrane is an extremely important cell part that functions as a barrier that completely surrounds the cell and serves as an animal cell's outer barrier. It is composed of a lipid bilayer. The lipid bilayer is made up of a double layer of fatty acids that have a hydrophobic interior and a hydrophillic exterior. Embedded within the membrane are proteins and other structures that help regulate what enters or exits through the membrane.
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Mitochondria
The mitochondria, AKA the "Powerhouses of the cell," are, as their name suggests, structures that supply energy for the cell. Inside these organelles there are many folded membranes called christae that contain the necessary compounds for aerobic respiration. (For more information, see the linked page). Cells that have a high energy requirement such as muscle cells have more of these structures.
Golgi Bodies
Golgi Bodies are structures that take the form of stacks of membranes and function to pack and modify proteins for exportation outside of the cell. Their function can be remembered by the phrase "GB Packers," which is a reference to the American football team the Green Bay Packers. These structures also function to form the vesicles that are used in Active Transport.
Lysosomes
Lysosomes are digestive structures that help to break down waste and other materials in a cell. Some immune cells use lysosomes to destroy viruses and bacteria that they take in through Endocytosis.
Smooth Endoplasmic Reticulum
The Smooth Endoplasmic Reticulum is a structure that is composed of membranes that is responsible for synthesizing steroids within cells and breaking down toxins in the liver. This structure is sometimes abbreviated SER.
Rough Endoplasmic Reticulum
The Rough Endoplasmic Reticulum is another structure composed of membranes. It is very similar to the smooth endoplasmic reticulum but is covered in ribosomes to synthesize proteins that give it a rough appearance. It plays a role in synthesizing compounds for the cell.
Ribosomes
Ribosomes are small structures made of RNA and Protein that function in protein synthesis to create proteins for the cell out of amino acids. They are formed in the nucleolus, which is found inside the nucleus. Besides free ribosomes that are found floating in the cytoplasm, ribosomes are also attached to the rough endoplasmic reticulum.
Cilia and Flagella
These structures are hair-like in form and can be found on the outside of a cell. If they are short and numerous, they are called cilia. If they are long, tail-like, and few, they are called flagella. Both serve to propel the cell along but cilia can also be used in specialized applications such as in the human nasal cavity to remove dust and foreign particles from the respiratory tract. They are only found on animal cells.
Plant-Only Organelles
The following organelles are only present in plants. However, the vacuole can sometimes rarely be found within animal cells, however it can be found in a much smaller form.
Cell Wall
The Cell Wall is a rigid structure mainly made out of the carbohydrate cellulose, a tough chemical that helps plants to maintain their shape and structure. When plant cells divide, a new cell wall is formed between the two dividing cells to separate them. This structure has pores that allow materials to move in and out of the cells.
Vacuole
Although some animal cells have this organelle, most of them are small. However, in plant cells, vacuoles are often very large and often take up much of the space in the cell. They hold water, food, or waste for the cells. However, the most common application for them in plant cells is to store the large amounts of water needed by the cell for photosynthesis.
(Note - although this organelle is also found animal cells, the vacuoles from plant cells are drastically bigger and play a much more important role in the processes of the cell. My chemistry teacher included them as plant cells, so I did too!)
(Note - although this organelle is also found animal cells, the vacuoles from plant cells are drastically bigger and play a much more important role in the processes of the cell. My chemistry teacher included them as plant cells, so I did too!)
Chloroplast
The Chloroplast is a structure found in plant cells that provides the necessary structures for photosynthesis. It is filled with the chemical chlorophyll which is a vital compound to facilitate photosynthesis. It has an inner and outer membrane and has several different kinds of molecules within it that allow the process to take place. See the photosynthesis page under the biochemistry heading for more information.