Cellular Biology is one of the most complex parts of all biology requiring knowledge in almost all aspects of science. But enough with the intro time, lets get down to the science stuff...
The Cells Organelles
The Cell is a very complex thing and has many different parts to it, each of one those parts is called an organelle. There are various different organelles. Below is a cross section diagram of a typical animal cell. Each of the major different organelles are labelled |
| A simple diagram of an animal cell of which I am concentrating on for part 1. http://media-3.web.britannica.com/eb-media//02/114902-050-0D7352BF.jpg |
The Nucleus
The nucleus holds all of the information that the cell requires to function. The DNA is held within the central part of the nucleus and is effectively an enormous instruction manual of how to make proteins. The DNA is read by messangerRNA by unzipping the DNA strand and making a single sided copy of it RNA. RNA is then fed out of the nuclear envelope through tiny pores in it. this is then fed to the ribosomes.
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| The Nucleus is marked by the larger brackets and the Nucleolus is marked by the smaller brackets on the left. Notice the ER around it. |
Ribosomes
Ribosomes are the smallest organelles in the cell being only two large proteins. Ribosomes use mRNA to code for making proteins. The proteins are made by lots of strands of tRNA - which has amino acids attached to it - attaching themselves to the RNA in the ribosomes. These amino acids then attach together to form long proteins.These are then extruded either into the cytoplasm or into the rough endoplasmic reticulum.
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| The two proteins that join together to make a ribosome |
The Rough and Smooth Endoplasmic Reticulum
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| The rough ER is in the bottom and left with the nucleus in the top right. Note that the ER is much larger and more of a mess in real life than it is in the diagrams. http://www.visualphotos.com/photo/1x8466307/rough_endoplasmic_reticulum_tem_9c3023.jpg |
The endoplasmic reticulum is a series of interconnected tubes and vesicles that allow proteins to move around, it also is used in the synthesis of vesicles and processing proteins that are formed within it. Ribosomes dock to the outside of the rough ER giving it it's rough appearance. These squirt the proteins into the ER as they are being made. The proteins are then ejected out of the smooth ER in little sacks made out of fatty acid membranes, the same stuff that the cell membrane is made of. These sacks then perform a variety of tasks. The smooth ER also completes a variety of other tasks.
The Golgi Apparatus
The Golgi apparatus takes a lot of the vesicles produced by the ER and then further processes the proteins inside them and then repackages them. It is effectively the cells post office and packages or repackages different proteins in vesicles for use within the cell or for going outside of the cell to other cells. |
| The Golgi apparatus is highlighted in range and yellow, note that there are many vesicles next to the Golgi apparatus. The nucleus is in the bottom left. http://faculty.ccbcmd.edu/courses/bio141/lecguide/unit1/proeu/images/12204b.jpg |
Peroxisomes
Peroxisomes are vesicles that are effectively the cells rubbish bins. They contain enzymes that can break down molecules and neutralise free radicals. The proteins within reduce the free radicals by removing the extra electrons that they have. The extra electrons make these chemicals highly reactive.Lysosomes
Lysosomes are vesicles that contain digestive proteins. They are effectively the cells recyclers. They can recycle anything, from large organelles to viruses that enter the cell.
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| A diagram of a simple bi-layer lipid vesicle of which lysosomes and peroxisomes both are. Note the cell membrane is made out of the same bi-layer lipid membrane. In Lysosomes and Peroxisomes the key bit lies within the vesicle http://journalofcosmology.com/images/LipidVesicle578.jpg |
Mitochondria
Mitochondria are some of the cells largest organelles. They function as the cells powerhouses, producing Adenosine TriPhosphate from glucose. ATP is effectively the cells currency and is needed by the cell for almost anything. ATP is the cells go to chemical energy source for everything. Mitochondria are unusual in the fact that they have their own DNA. The DNA is used for controlling the organelles processes and for replicating itself, which only chloroplasts can do as well.
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| Mitochondria, note the folded inner membrane. http://scienceblogs.com/transcript/mito0.jpg |
Centrosome
The centrosome is the organelle that creates and organises the cytoskeleton which is made out of a long rigid tube like protein called actin. the cytoskeleton is crucial in moving large molecules and vesicles around the cell. The Centrosome is also crucial in cell division as it gives the cell its "spindles" to move the chromosomes to each side of the cell. |
| The centrosome, Note the centricle in the middle, the two white cylindrical bodys. http://www.wadsworth.org/bms/SCBlinks/web_mit2/RES_MIT.htg/cen_par.gif |
Cillia
Cillia are tiny motile hair like structures found on the outside of cells, in bacteria they are used for movement. In animals they are often used for moving liquids and mucus around the body. They wave around in a synchronised fashion creating tiny currents in a fluid.
The Cell Membrane
The cell membrane is formed out of they same stuff that vesicles are, however it is much larger and more complex. The primary function of the cell membrane is to contain the cell and to stop its organelles floating off. However it also regulates the flow of chemicals in an out of the cell and prevents crucial chemicals floating out. The cell membrane is made out of a bi-layer of fatty acids just as vesicles are. the fatty acids have a hydrophobic end and a hydrophilic end. The hydrophobic ends join together in the middle to form a bi-layer.
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| A diagram of the cell membrane. Note the double layer of fatty acids. Also note the channel proteins that are used in controlling the movement of materials in and out of the cell, through the membrane. http://upload.wikimedia.org/wikipedia/commons/f/fd/Cell_membrane3.png |
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