* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Intermediate Filaments
Survey
Document related concepts
Embryonic stem cell wikipedia , lookup
Biochemical cascade wikipedia , lookup
Vectors in gene therapy wikipedia , lookup
Polyclonal B cell response wikipedia , lookup
Artificial cell wikipedia , lookup
Cytoplasmic streaming wikipedia , lookup
Cellular differentiation wikipedia , lookup
Cell culture wikipedia , lookup
Adoptive cell transfer wikipedia , lookup
Neuronal lineage marker wikipedia , lookup
Cell-penetrating peptide wikipedia , lookup
Symbiogenesis wikipedia , lookup
Cell growth wikipedia , lookup
State switching wikipedia , lookup
Organ-on-a-chip wikipedia , lookup
Cell theory wikipedia , lookup
Cell (biology) wikipedia , lookup
Transcript
First stage 28/12/2015 Biology Lec 1 بثينة.د Cell Biology Cytoskeleton The cytoskeleton is a network of fibers throughout the cell's cytoplasm that helps the cell to maintain its shape and gives support to the cell and enables cellular motion such as cilia and flagella and plays important roles in both intracellular transport , )the movement of vesicles and organelles, for example) and cellular division .The cytoskeleton is made up of three kinds of protein filaments: 1- Actin filaments (also called microfilaments) 2- Intermediate filaments 3- Microtubules Cytoskeleton Microfilaments Microfilaments are fine rigid hollow rods ,5- 7 nm in diameter, represent the active or motile part of the cytoskeleton. Made of a contractile protein known as actin. Actin appears in a globular form (G-actin). Microfilaments are long polymerized chains of the (1) molecules are intertwined in a helix, creating a filamentous form of protein (F-actin). Microfilaments considered part of the cell cortex, which regulates the shape and movement of the cell’s surface. Functions of microfilaments: 1- Provides mechanical strength to the cell 2- Link transmembrane proteins (e.g., cell surface receptor) to cytoplasmic proteins. 3-Anchors the centrosomes at opposite poles of the cell during mitosis. 4-Pinches the dividing animal cells during cytokinesis. 5-Supports the plasma membrane. 7-Microfilaments association with the protein myosin is responsible for muscle contraction. 8- They function in the maintenance of cell-shape. 9- These filaments are associated with membrane activities such as endocytosis and exocytosis. Microfilaments Microtubules Microtubules are hollow cylindrical tubes, 20- 25 nm in diameter (lumen = approximately 15nm in diameter), most commonly comprised of 13 protofilaments which, in turn, are polymers of alpha and beta tubulin .They have a very dynamic behavior, binding GTP for polymerization. (2) In animal cells, microtubules arise from a region of the cell called the microtubule organizing center (MTOC) located near the nucleus. In nine triplet sets (star-shaped), they form the centrioles ,and in nine doublets oriented about two additional microtubules (wheelshaped) they form cilia and flagella. They play key roles in: Determine cell shape and in a variety of cell movements, including some form of cell locomotion, the intracellular transport of organelles, and the separation of chromosomes during mitosis. The axoneme of cilia and flagella . The mitotic spindle . Providing a pathway for intracellular movement of organelles and proteins. Microtubules (3) Intermediate Filaments Intermediate filaments have a diameter of about 10nm, which is intermediate between the diameter of two other principle elements of the cytoskeleton , actin filaments and microtubules. Like actin filaments, they function in the maintenance of cell-shape, its form a 'basket' around the nucleus. Filaments serving as structural components of the nuclear lamina and sarcomeres. Different intermediate filaments are: Vimentins, being the common structural support of many cells. Type I and type II: acidic keratin and basic keratin, respectively.Produced by different types of epithelial cells ( bladder, skin,etc). Neurofilaments of neural cells . Lamin inside the inner nuclear envelope, lamins are vital to the re-formation of the nuclear envelope after cell division. Desmin, found in muscle cells. Intermediate filaments (4) Centrosome In cell biology, the centrosome is an organelle that serves as the main microtubules organizing center ( MTOC) of the animal cell ,it is duplicated during S phase of the cell cycle . Centerioles , found only in animal cells, these paired organelles are located together near the nucleus. Each centerioles is made of nine bundles of microtubules (three per bundle) arranged in a ring. Just before mitosis, the two centrosomes move part until they are on opposite side of the nucleus and organized into a spindle-shaped formation that called spindle fibers.These spindle fibers act as indicator for the alignment of the chromosomes as they separate later during the process of cell division. Centosomes Cilia & Flagella Cilia & flagella are motile cellular appendages found in most microorganisms and animals, cilia function to move a cell or to help (5) transport fluid or materials past them. The respiratory tract in humans is lined with cilia that keep inhaled dust, and harmful microorganisms from entering the lungs. Cilia are usually shorter and occur together in much greater numbers than flagella. In eukaryotic cells, cilia and flagella contain the motor protein (dynein) and (microtubles), the core of each of the structures is termed the (axoneme) and contains two central microtubules that are surrounded by an outer ring of nine doublet microtubules. Dynein molecules are located around the axoneme. A plasma membrane surrounds the entire axoneme complex, which is attached to the cell at a structure termed the basal body. Basal Body: Basal body (also known as a kinetosome). Basal bodies maintain the basic outer ring structure of the axoneme of the cilia and The basal body is structurally identical to the centrioles. Inclusions: Inclusions: are considered to be nonliving components of the cell that neither possess metabolic activity nor are bounded by membranes. The most common inclusions are glycogen, lipid droplet, pigments, and crystals. 1-Glycogen: Glycogen is the most common storage form of glucose in animals and is especially abundant in cells of muscle and liver. 2-Lipids: is a storage forms of triglycerides, are stored in specialized (6) cells, adipocytes, also located as individual droplets in various cell types. Especially those of the liver, lipids are source of energy. 3- Pigments: there are deposits of colored substances include: A- Melanin: the most common pigment in the body, its dark brown pigment present in the skin, hair, retina, and some parts of the central nervous system (C.N.S) B-Lipofuscin: its yellow to brown pigment found in long lived cells, like neurons of the C.N.S and cardiac muscles. Lipofuscin pigments are membrane-bound and represent the indigestible remnants of lysosomal activity. C- Hemosiderin: it’s a cold-yellow pigment. It’s the end product of Hb degradation of old red blood cells. They are present in the liver, spleen and bone marrow. D- Crystals: crystals are structures of crystalline forms of certain proteins . They are not commonly found in cells, with the exception of steroid cells, and interstitial cells of testes, and occasionally in macrophages. Ultrastructure of basal body (7)