Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Membranes of Living Organisms Outline
Document related concepts
Protein phosphorylation wikipedia , lookup
Cell growth wikipedia , lookup
Cell culture wikipedia , lookup
Cell nucleus wikipedia , lookup
Cellular differentiation wikipedia , lookup
Cell encapsulation wikipedia , lookup
Magnesium transporter wikipedia , lookup
Extracellular matrix wikipedia , lookup
Cytokinesis wikipedia , lookup
Organ-on-a-chip wikipedia , lookup
Cell membrane wikipedia , lookup
Signal transduction wikipedia , lookup
Transcript
Outline Membranes of Living Organisms Membrane Structure Diffusion and Osmosis Why membrane proteins are important Transport across the membrane – Transport of small molecules – Transport of large molecules 2 Phospholipid Structure Hydrophilic Polar Head Phospholipid bilayer Hydrophilic heads Water Hydrophobic tails Hydrophobic Nonpolar Tails Hydrophilic heads Water Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Fluid Mosaic Model of Cell Membrane Glycoprotein Phospholipid Bilayer Carbohydrate Outside Cell Glycolipid Cell Membrane Components 1. Phospholipid bilayer 2. Membrane proteins 3. Carbohydrates 4. Cholesterol Cholesterol Protein Fluid Mosaic Model of Membrane Structure Protein Cytoplasm (inside cell) Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 1 Roles of Membrane Proteins Roles of Membrane Proteins Cell surface identity marker Cell adhesion Cytoskeleton attachment Signal Transduction Enzyme Transport Messenger molecule Protein Receptor Activated molecule ATP Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Osmosis is Water Diffusion Across a Semipermeable Membrane Diffusion Solute dissolves in a solvent. Lump ofSolutes sugar move from a high to a low concentration. Sugar molecule Solute molecule Water molecules Selectively permeable membrane Figure 5.17 How animal & plant cells behave in different solutions External environment of a cell can vary Hypertonic Isotonic Hypotonic H2O H2O H2O H2O Animal cell Osmoregulation – Controlling Water Balance Osmotic Survival Mechanisms 1. Extrusion Contractile vacuoles (2) Lysed (1) Normal H2O H2O (3) Shriveled Plasma membrane H2O H2O Plant cell 2. Isotonic solutions Blood protein albumin 3. Live with it (4) Flaccid Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings (5) Turgid (6) Plasmolysis (shriveled) Turgor pressure 12 2 Moving Molecules into & out of Cells Moving Molecules into or out of Cells Proteins act as channels PROTEINS – control movement into or out of cells K+ ion channel Solute molecule Passive Transport – Cell energy not required Channels Carriers Pores Active Transport – Requires cell energy (ATP) Pumps Exocytosis Endocytosis Side view Transport protein Moving Molecules into or out of Cells Passive transport of 1) Water-soluble molecules 2) Ions Moving Molecules into or out of Cells Proteins act as pores Proteins act as carriers Passive transport of 1) ions 2) Sugars 3) amino acids Top view Facilitated Diffusion in Red Blood Cells 1) Cl- and bicarbonate ions 2) Glucose carrier Porin Protein Pleated folds Porins are transport pores 1.Allow movement of small molecules Water Ions Organic Wastes Outside cell 2003 Nobel Prize in Chemistry Aquaporin Water Channels Inside cell Aquaporins are Water Channels Major Sites of Expression Comments Aquaporin-0 Aquaporin-1 Aquaporin-2 Aquaporin-3 * Aquaporin-4 Aquaporin-5 Eye: lens fiber cells Fluid balance within the lens Red blood cells Osmotic protection Kidney: proximal tubule Concentration of urine Eye: ciliary epithelium Production of aqueous humor Brain: choriod plexus Production of cerebrospinal fluid Lung: alveolar epithelial cells Alveolar hydration state Kidney: collecting ducts Mediates antidiuretic hormone activity Kidney: collecting ducts Reabsorbtion of water into blood Trachea: epithelial cells Secretion of water into trachea Kidney: collecting ducts Reabsorbtion of water Brain: ependymal cells CSF fluid balance Brain: hypothalamus Osmosensing function? Lung: bronchial epithelium Bronchial fluid secretion Salivary glands Production of saliva Lacrimal glands Production of tears Moving Molecules into or out of Cells Active transport occurs against a concentration gradient. Active Transport proteins that move molecules = Pumps Transport protein Solute 1 Solute binding ATP P ADP 2 Phosphorylation Protein changes shape 3 Transport P Phosphate detaches P 4 Protein reversion 3 Exocytosis and endocytosis transport large molecules across membranes Moving Molecules into or out of Cells A cell uses two mechanisms for moving large molecules across membranes Exocytosis Æ transfers molecules into cells – Exocytosis is used to export bulky molecules, such as proteins or polysaccharides – Endocytosis is used to import substances useful to the livelihood of the cell In both cases, material to be transported is packaged within a vesicle that fuses with the membrane Copyright © 2009 Pearson Education, Inc. Fig. 04.15 Moving Molecules into or out of Cells Examples of Transport Across Cell Membranes Endocytosis Æ transfers molecules into cells Endocytosis of a Bacterial Cell 21 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fig. 6.18 (TEArt) Sodium – Potassium Pump Extracellular PP ATP P A Na+ PP P ATP A Intracellular 1. Protein in membrane binds intracellular sodium. 2. ATP phosphorylates protein with bound sodium. K+ Example: Active Transport and Passive Transport P PP ADP A 3. Phosphorylation causes conformational change in protein, allowing sodium to leave. P PP A ADP 4. Extracellular potassium binds to exposed sites. P PP A ADP+Pi 5. Binding of potassium causes dephosphorylation of protein. PP ATP P A 6. Dephosphorylation of protein triggers change back to original conformation, potassium moves into cell, and the cycle repeats. 4 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Example: Carrier - Mediated Endocytosis Example of Neurotransmitter Movement from Cell to Cell Coated pit Clathrin Receptor protein Coated vesicle Reuptake transporter Summary of Transport Mechanisms Molecular Transport Passive transport - movement from high to low concentration ¾Movement through proteins ¾Channels & carriers & pores Active transport - movement from low to high concentration ¾Movement through proteins ¾Pumps Æ Require ATP (energy source) END Membranes & Transport ¾Bulk Transport – requires entire membranes Exocytosis Endocytosis 5
