It goes without saying that the functioning of the human organism is a complicated process. Cells are mainly categorized as either eukaryotic or prokaryotic. Regardless of the classification, both prokaryotic and eukaryotic cells share a lot in common. Both of them are surrounded by a semi-permeable plasma membrane that has a bilayer of phospholipids. This plasma membrane contains cytoplasm that is majorly made up of fluid and organelles. Bacteria that fall in the kingdom Monera is the most recognized member of the prokaryotes. The prokaryotes have DNA that is not enclosed in a nuclear envelope that other prokaryotic cells have. The prokaryotes, as opposed to other prokaryotic cells, do not have some other organelles like the mitochondrion that helps in the energy transduction process and the chloroplast. Apart from bacteria that are classified as prokaryotes, the other members of the four kingdoms are categorized as eukaryotes.
Eukaryotes have a true nucleus that has a true nuclear envelope that is bilayer. The nucleus is where genetic material is located. The nucleus in both eukaryotic and prokaryotic cells helps in directing cells’ chemical activities. The eukaryotic nucleus has a long of chromatin containing DNA and corresponding proteins. There is the lumen, a space that separates two membranes. The prolongation of the lumen is the Endoplasmic reticulum. There are types of endoplasmic reticulum: rough and smooth. The rough endoplasmic reticulum is closer to the nucleus than the smooth endoplasmic reticulum. Smooth endoplasmic reticulum forms a site where proteins are manufactured and stored before they are transported to other destinations in the cells. Vesicles, which exist as pieces of smooth endoplasmic reticulum, run from the smooth ER to other parts of the cells where they deliver their contents.
Rough endoplasmic reticula have ribosomes attached to their surfaces. These organelles help in protein synthesis. Without ribosomes, protein synthesis within the cells. Ribosomes are made up of RNA and proteins that are manufactured in the nucleus from where they are transported to the cytoplasm. The chemical composition of the prokaryotic and eukaryotic ribosomes are different hence the ability of certain antibiotics like tetracycline and streptomycin to interfere with the bacterial ribosomes’ capability to synthesize protein without interfering with the host cells’ ribosomes.
Vacuoles and vesicles are storage organelles. However, vacuoles differ from the size of the vesicles. Plant cells are synonymous with a large central vacuole that occupies the largest portion of the cell. It is basically used for storing an assortment of molecules. Contractile, found in Paramecium, helps in the secretion of water from the cell. Compared to the vacuole, vesicles have a very small size and have an important role in moving the elements within the cell. In fact, vesicles can also move to the Golgi apparatus, which is a membrane structure of the eukaryotic cells, organelle, mainly designed to remove substances that are synthesized in the endoplasmic reticulum.
Golgi bodies do a controlling function within the cell. Materials that are received like the vesicles become one entity with the Golgi body and then sent to various sections of the cell. The Golgi apparatus is the storage of some elements and materials that, in turn, participate in different reactions.
Many eukaryotic cells have mitochondrion. Mitochondrion helps in cellular respiration. They have a double membrane with an outer smoother membrane and an inner membrane that is folded into cristae. Intermembrane space is the space between the two membranes. The space that exists inside the inner membrane is known the as mitochondrion matrix.
Chloroplasts are never found in animal cells as they mainly function in plant cells helping to transform light energy to chemical energy. To facilitate this important function, Chloroplasts have chlorophyll, a green pigment that helps in energy formation. Intermembrane space divides chloroplasts from each other. Studies suggest that mitochondrion and chloroplasts may have arisen from prokaryotic invaders bearing that these two organelles have their own genetic material separate from that found in the nucleus. These organelles are capable of controlling their own protein synthesis and replication at the same time. Some other evidence that has been adduced include the fact that they are surrounded by bilayer membranes. In the process, one membrane comes from the invading cell and the other one from the plasma membrane.
Another organelle is the cytoskeleton whose building units are special proteins. Globular proteins are provided with microtubules. Cilia, flagella, and centrioles are mainly the only places it may be found in. Microtubules are arranged in a nine-plus-two formula in cilia and flagellum as opposed the to 9-sets-of-3 arrangement in centrioles. Microfilaments also comprise the cytoskeletons.
Cells do secret hormones or cytokines that communicate with the cells far away from where they are. This is a hormone signaling mechanism and is a very common means of communication among eukaryotic cells. Communication can also take place through the Juxtacrine mechanism where molecules on the surface of a target cell can be sensed by a cell closer to it. This is very important in immune cell activation and extravasations.