BIOE 1010 Week 14 Notes
BIOE 1010 Week 14 Notes BIOE 1010
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This 4 page Class Notes was uploaded by Sara Littlejohn on Thursday April 7, 2016. The Class Notes belongs to BIOE 1010 at Clemson University taught by Dr. Vladimir Reukov in Spring 2016. Since its upload, it has received 12 views. For similar materials see Biology for BioEngineers in Bioengineering at Clemson University.
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Date Created: 04/07/16
Module 7: Integrating Cells into Tissues 4/6/2016 The Cytoskeleton o A dynamic structure continuously reorganized o Built from three types of protein filaments Actin Filaments (Microfilaments) Microtubules Stiff hollow tubes formed by the polymerization of tubulin They can rapidly disassemble in one location and reassemble in another, growing out from the centrosome During cell division, microtubules form the mitotic spindle, the machinery that will segregate the chromosomes equally between the two daughter cells Intermediate filaments Ropelike fibers (polymers) with great tensile strength Function: to withstand mechanical stress that occurs when cells are stretched Built from: keratin in epithelial cells, vimentin in fibroblasts and muscle cells, neurofilament in nerve cells, and nuclear lamins in the nucleus o Gives cells the ability: To adopt a variety of shapes To organize many processes inside the cell ( ex. Mitosis, organelle traffic) To interact mechanically with the environment To carry out coordinated movements Microtubules and motor proteins are involved in organelle traffic in the cell o Kinesins and dyneins: motor proteins that use the energy from ATP hydrolysis to move along the microtubules and carry specific membrane vesicles and other cargoes Actin Filaments: o Two stranded helical polymers of actin o Dispersed throughout the cell, highly concentrated in the cortex o Assemble and disassemble in cell locomotion Cell crawling depends on actin o Protrusion: actin polymerization at the leading edge of the cell pushes the plasma membrane forward o Attachment: new points of anchorage are made between the actin filament and the surface o Traction: contraction of the rear of the cell draws the body of the cell forward During contraction actin filaments slide against myosin filaments Muscle contraction depends on bundles of actin and myosin Tissues The extracellular matrix: an intricate network of macromolecules filling the extra cellular space Proteoglycans and GAGs form a highly hydrated gel-like “ground substance” in which the fibrous proteins are embedded and cells are held together Macromolecular composition of ECM o Two main classes: Polysaccharide chains: glycosaminoglycan (GAGs), usually fund covalently linked to protein in the form of proteoglycans Proteins with structural and adhesive functions: Collagen Elastin Fibronectin Laminin ECM forms o Calcified in rock-hard structures: bone, teeth o Transparent: cornea o Ropelike organization that gives tendons their enormous tensile strength o Flexible, thin tough mats around or under the cells: basal lamina (basement membrane) Role of matrix components o Polysaccharide gel resists compressive forces on the matrix while permitting the rapid diffusion of nutrients, metabolites, and hormones between blood and the cells o Collagen fibers strengthen and help organize the matrix o Rubberlike elastin fibers give resilience o Adhesive proteins help cells attach to matrix The collagen triple helix ( a unique 3-D structure) o 1 Collagen molecule = 3 Helical Chains that wrap around one another, due to a specific repeating tripeptide unit: Gly-Pro-Hyp Collagen molecules (tropocollagen) are cross-linked together to form collagen fibrils. Fibrils aggregate and form fibers. Cell Adhesion Molecules (CAMs) o Cadherins (cell-cell) are linked to the cytoskeleton o Integrins (cell-matrix) are linked to the cytoskeleton Cell junctions hold cells together in TISSUES TISSUES = CELLS + EXTRACELLULAR MATRIX (ECM) Tissue Classification o Connective Tissue Binds structures and fill spaces Cells: fibroblasts, macrophages, mast cells Provides support and protection o Epithelial Tissue Covers organs and the body Lines body cavity Cells tightly packed Functions: protection, secretion, absorption o Muscle Tissue Skeletal Muscle (attached to bones) Smooth Muscle (walls of organs and blood vessels) Cardiac Muscle o Nervous Tissue Found in brain, spinal cord, and peripheral nerves Neurons and neurological cells o Cells form Tissues o Tissues form Organs o Organs form Organ Systems
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