CYTOSKELETON :The cytoskeleton is a network of protein fibers that dominate the cell and function in cell reality and structure. Filaments in eukaryotic cells, there are three types of such microfilaments , intermediate filaments and microtubulesMICROFILAMENTS ( ACTIN FILAMENTS )Actin filaments are welldefined filaments with a width of 6-8 nanometer. The filaments are formed by the ATP dependent polymerization of actin monomer into a characteristic linear from in which the subunits are arranged in a single tight zigzag helix to produce the superficial appearance of a double spiral with a distance.
Actin cytoskeleton are attached to the plasma membrane either directly or indirectly through a variety of membrane associated. INTERMEDIATE FILAMENTS Intermediate filaments include a family protein filaments about 10 nanometer thick, it can found in different of cell types. Just like microfilaments, intermediate filaments give the cell tensile strength and provide structure stability. Intermediate filaments compose the nuclear lamina, are found in the cytoplasm as well as outside the cell. MICROTUBULES Microtubules are polymeric fibers with hallow cylinders about 24 nanometer of varying length.
Microtubules are polymers of tubulin. There are two major forms of this protein alpha and beta tubulin. Each protein subunits is about 5 nanometer across and microtubules in transverne section are made up a ring of such globular subunits.CILIACilia are shorter and more numerous but have the same chemical composition and basic arrangement. Cilia are found mainly among protozoa. Cilia move in coordinated manner, like oars on a large boat. Cilia are found on the cells of our bronchial tract.
FLAGELLA Flagella are found in both prokaryotic and eukaryotic cells. It functions in locomotion and gives the cell the ability to move through it fleid envirement. How ever, although flagella in eukaryotes and prokaryotic servers the same function , the structure , the composition and mechanism by which it works different. PROKARYOTIC FLAGELLA The motor of the prokaryotic flagellum is the basal apparatus, a system of embedded in the cell wall and plasma membrane (TEM). ATP-driven pump transport protons out of the cell, and the diffusion of protons back into the cell powers the basal apparatus, which turns a curved hook. EUKARYOTIC FLAGELLAIn eukaryotic, the flagellum is composed of protein filaments, called microtubules. One of the centrioles of the cell develops into the basal body, which then forms the flagellum. It consists of nine doublet pairs of microtubules arranged is a circular fashion around two central microtubules.The dynein motor protein utilize ATP to force the doublet microtubules to slide against one another creating a bending rection and propelling the cell forward.CENTRASOMESThe centrasomes is the microtubule- organizing centerof eukaryotic animal cells. It consists of two centrioles that are at eight angels with respect to another and which are embedded in a mass of proteins.Located in close prosimity to the nucleus, the centrosome is involved in the mitotic spindle fibers that separate the chromosomes during the cell division.The centrasome is also involved in creating and extending the microtubules thatconsitute the cytoskeletonsCENTRIOLES Centrioles are micro tubular cylinders about 1 nanometer long by 0.25 nanometer. At least two centrioles occur in all cels capable of division, usually lying close and at right angles to each other, together often termed a diplosome, within a dense region of cytoplasm, the centrosome.VACUOLESVacuoles are predominantly found in plants and fungi but also be found in animal cells. They are membrane- endosed organelles that shape, size and function depending on the cell type.. LYSOSOMESLysosomes are dense spheroidal membrane bounded bodies, they contain acid hydrolases able to degrade a wide variety of substances.The enzymes of lysosomes are formed in the rough endoplasmic and are modified within the golgiapportus. Once modified, they leave the golgi is secietery vesicles and fuse with endosomes to form the lysosomes.MICROBODIESMicrobodies are small, rephesecal membrane-enclosed organelles. There are two main types ” peroxisosomes and glyonysomes PEROXISOSMESPeroxisosmes are membrane bound vacuoles about 0.5- 0.15 nanometer across, composed chiefly of high concentrations of the enzyme urate oxidase. Oxidation is carried out by a number of enzymes. GLYONYSOMESGlyonysomes are also single membrane microbodies but only found in plant cells. It contains enzymes like isocratic lyase, malate synthese, glycolate cycle. It is involved in photorespiration and conversion of fats into carbohydrates.ENDOPLASMIC RETICULUMRight outside the nucleus of most eukaryotic cells is a network of membranous folds called the endoplasmatic reticulum ( ER). These folds consist of phospholipid blayer membrane that creates an environment separate from the cytosol. This space insidebthe ER is known as the ER lumen or cisternal space. The ER can be divided into 2 sections, the smooth and rough ER. ROUGH ENDOPLASMIC RETICULUMThe membrane folds found closest to the nucleus contain ribososmes that are embedded into the cytosol side of the ER membrane. These ribosomes function to synthesis proteins that ultimately are either embedded into the cell membrane ( integral ) or are destined to leave the cell entirely.The membrane of the rough ER is physically connected to the nuclear envelope. Because of this, the perinuclear space is connected to the ER lumen. Once the proteins in the rough ER are synthesized, they are forced into the ER lumen and travel to the smooth ER. SMOOTH ENDOPLASMIC RETICULUMThe smooth ER contains folds that are slightly more tubular than the folds of the rough of the rough ER. Unlike the rough ER, the smooth ER does not contain any embedded ribososmes.Since it does not contain ribososmes, the smooth ER is not included in the the synthesis of proteins. However, it does contains special enzymes involved in the generation of glucose. Perhaps one of the most important coles of the smooth ER is the synthesis of lipids, such as fatty acids, phospholipids and cholesterol..GOLGI APPORATUSThe golgiapporatus is a series of flattened, membranous sacs known as cisternae. It is a relatively large structure that is net too far form the smooth ER. Once proteins are synthesized in the rough ER, they travel through the smooth ER, go into the cytosol in the secrectory vesicles, which are shutted to the golgi. In the golgi the proteins are organized, modified and shipped to their respective destination. INTRACELLULAR JUNCTIONSInterace;llular junctions cells are connected to each other, interacellular junction fundamental to the interactions between cells also allow coordination of activities of individual cells in a system. They also enables each systems to function as an integrated whole. TIGHT JUNCTIONA specialized connection of two adjacent animal cell membrane, such that, space usually lying between them is absent, also known as occulating junctions and zonulae occuladentes. Tight junctions contain plasma membranes, which are very tightly pressed against each other due to bound proteins. GAP JUNCTIONSGap junctions are the connective tunnels that exist between adjarents cells. They allow molecules and ions up to a certain size to pass through from one cell to the next.Gap junctions are found in muscle tissue such as cardiac cells. There, they play an important role in allowing calcium ions to move across cells, which propogates the action potential and ultimaletyeauses the contraction of the heart. DESMOSOMESThey attach to intermediate filaments made of a protein called keratin; they hold two adjacent cells tightly together at a localized region.Desmosomes do not prevent the movement ions or molecules around cells but they are usually found in combination with tight junctions which do . Desmosomes are located in tissue that undergoes a constant stretching and pressure.
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