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Transcript
Membranes & Cell Transport LE 3-1 Cells lining intestinal tract Blood cells Smooth muscle cell Ovum Bone cell Sperm Neuron in brain Fat cell LE 3-2 Cilia Secretory vesicles Cytoplasm Mitochondrion Plasma (cell) membrane Nuclear envelope surrounding nucleus Chromatin (DNA) What do membranes do? •Form the boundary between the intracellular compartment and the extracellular environment. •“Traffic Cop” - Regulate what enters and leaves the cell = “selective permeability.” •Respond to substances that come in contact with the membrane. Ex: insulin, glucagon, & other hormones •Secrete (=squeeze out) substances that are synthesized inside the cell. •Compartmentalize and organize the interior of the cell. Ex: mitochondria, E.R., various vesicles Early evidence for the bi-layered structure of the plasma membrane came from transmission electron micrographs. This is the plasma membrane of a RBC. A phospholipid bilayer – This is NOT a functional membrane Here is a detailed picture of the way six phospholipid molecules interact with each other and their surroundings to form a phospholipid bilayer. Phospholipid Animation (Click Here) LE 3-3 EXTRACELLULAR FLUID Carbohydrate chains Phospholipid Protein bilayer with channel Hydrophobic tails Proteins Cell membrane Cholesterol Protein with gated channel Proteins Hydrophilic heads Cytoskeleton CYTOPLASM LE 3-5 EXTRACELLULAR FLUID Lipid-soluble molecules, O2 and CO2 diffuse through membrane lipids. Plasma membrane Large CYTOPLASM molecules that cannot diffuse through lipids cannot cross the membrane unless they are transported by a carrier mechanism Channel protein Small water-soluble molecules and ions diffuse through membrane channels LE 3-4 Diffusion = spreading of molecules from a place where the concentration [ ] is higher to a place where it’s lower. OSMOSIS = diffusion of H2O, across a membrane, from a region of higher [H2O] to a region of lower [H2O]. “[ ]” means “concentration of…” Gray dots represent solute particles. Solute = anything dissolved in the water. LE 3-6-1 Two solutions containing different solute concentrations are separated by a selectively permeable membrane. Water molecules (small blue dots) begin to cross the membrane toward solution B, the solution with the higher concentration of solutes (larger pink circles). A B Water molecules Glucose molecules Selectively permeable membrane LE 3-6-2a At equilibrium, the solute concentrations on the two sides of the membrane are equal. The volume of solution B has increased at the expense of that of solution A. Volume increased Volume decreased Diffusion & Osmosis Animations http://www.biologycorner.com/bio1/diffusion.html http://www.tvdsb.on.ca/westmin/science/sbi3a1/Cells/Osmosis.htm http://www.stolaf.edu/people/giannini/flashanimat/transport/osmosis.swf LE 3-7a Isotonic Water molecules LE 3-7b Hyp0tonic Water molecules LE 3-7c Solute molecules Hypertonic Hypertonic LE 3-8 Glucose molecule attaches to receptor site EXTRACELLULAR FLUID Change in shape of carrier protein Receptor site Carrier protein CYTOPLASM Glucose released into cytoplasm LE 3-9 EXTRACELLULAR FLUID 3 Na+ Sodium– potassium exchange pump 2 K+ ATP ADP CYTOPLASM LE 3-10 EXTRACELLULAR FLUID Ligands binding to receptors Ligands Endocytosis Exocytosis Ligand receptors CYTOPLASM Coated vesicle Lysosome Ligands removed Fused vesicle and lysosome LE 3-11 Cell membrane of phagocytic cell Lysosomes Vesicle Foreign object Pseudopodium (cytoplasmic extension) EXTRACELLULAR FLUID CYTOPLASM Undissolved residue LE 3-12 Microvillus Microfilaments Cell membrane Mitochondrion Intermediate filaments Endoplasmic reticulum Secretory vesicle Microtubule LE 3-14a Endoplasmic reticulum EXTRACELLULAR CYTOSOL FLUID Lysosomes Cell membrane Secretory vesicles Transport vesicle Golgi apparatus Membrane renewal vesicles Vesicle incorporation in cell membrane LE 3-14b Exocytosis Transport Types Animations • http://www.wiley.com/legacy/college/boyer/04 70003790/animations/membrane_transport/me mbrane_transport.htm