Lecture #3 The Plasma Membrane & The Cytoskeleton and ECM
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Lecture #3 The Plasma Membrane & The Cytoskeleton and ECM The Plasma Membrane outside of cell (extracellular) extracellular matrix glycolipid carbohydrate tag on protein integral membrane proteins cholesterol phospholipid peripheral membrane protein cytoplasm of cell (intracellular) microfilaments of cytoskeleton The membrane phospholipid saturated fatty acid unsaturated fatty acid Phospholipids in a membrane WATER Hydrophilic head Hydrophobic tail WATER Movement of Phospholipids Lateral movement (~107 times per second) Flip-flop (~ once per month) Movement of Proteins EXPERIMENT Researchers labeled the plasma mambrane proteins of a mouse cell and a human cell with two different markers and fused the cells. Using a microscope, they observed the markers on the hybrid cell. RESULTS Membrane proteins + Mouse cell Human cell Hybrid cell Mixed proteins after 1 hour CONCLUSION The mixing of the mouse and human membrane proteins indicates that at least some membrane proteins move sideways within the plane of the plasma membrane. Membrane Fluidity Depends on Fatty Acid Saturation Fluid Unsaturated hydrocarbon tails with kinks Viscous Saturated hydroCarbon tails Cholesterol Affects Membrane Fluidity Cholesterol Integral Membrane Proteins Phospholipid lipid of membrane N-terminus alpha helix of protein C-terminus a Helix CYTOPLASMIC SIDE Integral Membrane Proteins may be anchored by the ECM or the cytoskeleton extracellular matrix plasma membrane intracellular cytoskeleton How do plasma membrane proteins get to the plasma membrane? 1 Transmembrane glycoproteins Secretory protein Glycolipid 2 Golgi apparatus Vesicle 3 Plasma membrane: Cytoplasmic face 4 Secreted protein Extracellular face Transmembrane glycoprotein Membrane glycolipid The Cytoskeleton Microtubule 0.25 µm Microfilaments Vesicle ATP Receptor for motor protein Motor protein (ATP powered) Microtubule Vesicles Microtubule of cytoskeleton 0.25 µm Components of the Cytoskeleton microtubules microfilaments intermediate filaments Centrosomes and Centrioles Centrosome Microtubule Centrioles 0.25 µm Longitudinal section of one centriole Microtubules Cross section of the other centriole Intermediate filaments in nerve cells Plant Cell Walls Plasma membrane Central vacuole of cell Secondary cell wall Primary cell wall Central vacuole of cell Middle lamella 1 µm Central vacuole Cytosol Plasma membrane Plant cell walls Plasmodesmata Extracellular Matrix of Animal Cells EXTRACELLULAR FLUID Collagen A proteoglycan complex Polysaccharide molecule Carbohydrates Core protein Fibronectin Plasma membrane Integrin Integrins Micro- CYTOPLASM filaments Proteoglycan molecule Intercellular Junctions Tight junction Tight junctions prevent fluid from moving across a layer of cells 0.5 µm Tight junctions Intermediate filaments Desmosome Gap junctions Space between Plasma membranes cells of adjacent cells 1 µm Extracellular matrix Gap junction 0.1 µm
