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Cells are the building blocks of life; they form tissues, which create organs that in turn create living organisms. However, cells in themselves are complex; they are built out of multiple organelles, they are all specialised for certain roles in the cell, and when working correctly they allows the cell to function correctly.
The Nucleus is the control centre of the cell it commands the rest of the cell.
The nucleus, which is only found in eukaryotic cells, is contained in almost every body cell, an exception to this is the red blood cell that contains no nucleus, as it requires a larger surface area for oxygen to bond with haemoglobin, and In contrast some skeletal muscles have multiple nuclei.
The Nucleus is separated from the cytoplasm by the nuclear envelop, a double membrane, with the outer membrane connected to rough ER, or rough endoplasmic reticulum (Mentioned later in the essay). The membrane controls the movement of substances between the cytoplasm and the nucleus, such as the selective transport of proteins.
Within the nucleus is the nucleoli, which contains both DNA and RNA, this is also the site of the assembly ribosomes, which play a vital role in protein synthesis.
Finally within the nucleus contains the genes, which control cellular structure and direct cellular activities, DNA and RNA in the nucleus allow for cellular division and replication.
The mitochondria are the powerhouse of the cell they change chemical energy into ATP.
The Mitochondria are some of the smallest parts of an animal cell, measuring at around 1.5 Micrometres by 2 Micrometres; they are just visible with the use of a light microscope. The main "job" of the mitochondria is to provide energy for the cell and in turn the body. Mitochondria are found in varying amounts in many cells in the body, ranging from a couple of hundred to several thousand. The factor that determines the amount of these organelles within a cell is the amount of physiological activity a cell is require to do: The higher the amount of activity the higher the mitochondria.
Some Cells such as sperm cells that are able to "Swim" to a woman's ovaries and fertilise a woman's eggs for reproduction, require large amounts of ATP (Adenosine triphosphate), or oxidized guyton, commonly referred to as "energy". This leads onto the point that the sperm cell has a larger number of Mitochondria than most cells within the body.
Other cells that contain large amounts of Mitochondria include those that are found in muscles, around the liver and within the kidneys; all of these areas use ATP at high rate and as such need the increased Mitochondria for this reason.
The Mitochondrion (singular Mitochondria) has two membranes (Much like the plasma membrane); the outer mitochondrial membrane, which is smooth and the inner mitochondrial membrane which is rough and is arranged in a series of folds call crisate.
The central fluid-filled cavity of a mitochondrion is called the matrix, and within the folds of the crisate this creates a massive surface area needed for the large amount of chemical reactions that are part of aerobic cellular respiration.
Rough Endoplasmic reticulum
The Rough Endoplasmic reticulum synthesizes proteins and other compounds.
The Rough Endoplasmic reticulum is a network of flatten sacs, called cisterns, covered in ribosomes (The reason for its name) the Rough ER is attached to the nucleus membrane and extends around the nucleus throughout the cytoplasm.
The rough ER is studded with ribosome and is the site of protein synthesis, the synthesized protein then enters the cisterns and is processed and sorted, this normally consists of the adding of enzymes.
The processed and sorted proteins may be used for a number of functions, involving other organelles.
Smooth Endoplasmic reticulum
The Smooth Endoplasmic reticulum synthesizes fats and steroids.
The smooth endoplasmic reticulum extends outwards from the rough ER and help to form a large network of membrane tubules. Unlike rough ER, smooth ER isn't studded with ribosome on the outer surface of its membrane.
However, smooth ER instead contains unique enzymes that mean that its functions are more diverse than that of its rough counter-part. Smooth ER synthesizes fats and steroids, such as oestrogen and testosterone.
In liver cells, the enzymes of the smooth ER help to release glucose into the bloodstream, as well as helping with the removal of harmful substances, such as inactive drugs, for example alcohol, and toxins.
The Golgi complex is the transportation route, rather like a post office, for proteins and other substances.
Most of the protein synthesized by the rough ER need to be transported around the cell, the first step of this transport process is through the Golgi complex. The Golgi complex consists of 2-30 cisterns. Most cells only have one Golgi complex, however there is a number of cells that have several, being more extensive in cells the secrete proteins throughout the body.
The Golgi complex, contains numerous enzymes that help to modify, sort and package proteins for transportation, the Golgi complex adds substances such as sugars and proteins to lipids, to help form more complex and beneficial substances.
The Golgi complex uses vesicles to transport substances; there are numerous different type for differing substances.
The Lysosomes are the stomachs of the cell and help digest substances.
Lysosomes are membrane-enclosed vesicles that are formed in the Golgi complex, inside are as many as 40 different enzymes that are capable of breaking down a large variety of molecules, since these enzymes work best at acidic pHs the lysosomes have active transport "pump" that move H+ molecules into themselves, to maintain a pH of 5.
Lysosomes allow the breaking down of sugars and amino acids that are used throughout the cell for a large number of functions.
Lysosome also recycle the cell's own structure, sometimes digesting organelles, breaking them down and then returning the substances used to make the organelle, this is the replacement of old wore out organelles and is called autophagy.
Also most of the digestive processes involving lysosomes occur within a cell; this is not always the case. The head of a sperm cell releases Lysosomal enzymes to help penetrate the surface of the ovum.
The Ribosomes are the sites of protein synthesis.
Ribosomes are the site of protein synthesis within the cell, made up of ribosomal RNA (rRNA) and proteins and contain high contents of ribonucleic acid. Some ribosomes are free ribosomes, these ribosomes are unattached to any structure, while Membrane-bound ribosomes, are attached to the nucleus membrane and the Rough ER.
The ribosomes that are Membrane-bound synthesize proteins that are normally destined for insertion into the plasma membrane or to be exported out of the cell for repair or growth within other parts of the body.
Centrioles play a role in the layout of the cell and in cell division.
The centrioles are normally located near to the nucleus, and are unique in the fact of their 9 x 3 layout, this layout is the nine group of triplets of microtubules, these microtubules are arranged is a circular.
The Centrioles play a role in the arrangement of the cell; the position of the centrioles within the cell set the layout of the cell and provides the placement of the nucleus, which in turn defines the location of other organelles.