Presentation on theme: "Cytoskeleton & Extracellular Components The cytoskeleton is a network of fibers that extend through the cytoplasm in the cell. There are 3 basic structures."— Presentation transcript:
Cytoskeleton & Extracellular Components The cytoskeleton is a network of fibers that extend through the cytoplasm in the cell. There are 3 basic structures of the cytoskeleton: Microtubules, Microfilaments, Intermediate Filaments.
Microtubules Hollow tubes made of tubulin (globular protein) – Centrosomes located near the nucleus in plants grow tubules outward resisting compression forces – Centrioles a set of 9 tubes set in a ring active in replication in animals – Flagella 9 + 2 arrangement propel using a whip-like motion mostly single per motile cell but can be double (or few) as well the flagellum is anchored to the basal body (later becomes the centriole in a fertilized egg) the bending movement comes from dyneim, a larger protein-comples that attaches the tubules – Cilia much like flagella but work in a rowing motion together there are usually many per cell
Microfilaments 2 intertwined strands of actin Actin – a double twisted rod – can be branched forming a fibrous network – gives the cortex (outer cytoplasmic layer) its semisolid consistency Muscle motor unit – long actin filaments bridged with myosin, a protein that "walks" the fiber causing contraction Pseudopodia (fake foot) – actin network that converts the solution into gel in ameoboid organisms Cytoplasmic streaming – a process in large plant cells where cytoplasm is directed to other parts of the cell to speed delivery of needed materials
Intermediate Filaments Fibrous keratin proteins supercoiled into thicker strands – Made of a family of keratin proteins – Permanent structures that persist long after the cell dies Skin, hair, nails Nuclear lamina – important in reinforcing the shape of the cell
Extracellular Components and Connections Between Cells Cell Walls (Plants) – protects – maintains shape – prevents excessive uptake of water – composed of microfibrils of cellulose embedded in a matrix of protein and polysaccharides – parts: primary cell wall - thin and flexible middle lamella - rich in pectins (polysaccharide) which glue cells together secondary cell - wall thick strong structure between the primary wall and the plasma membrane
Extracellular Components and Connections Between Cells Extracellular Matrix (animal cells) – consists mostly of glycoproteins (collagen) incorporated into the cell walls – creates a fibrous network that embeds itself into protoglycans (another fibrous glycoprotein) – fibronectins are glycoproteins attached to integrins on the outer membrane that transmit changes in the outer environment into the cells
Extracellular Components and Connections Between Cells Intercellular junctions – plasmodesmata (plants) channels where cytosol communicates between cells – Tight junctions (continuous seal around cell preventing leakage), – Desmosomes (fasten cells together into strong sheets) – Gap junctions (cytoplasmic channels from one cell to another)