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Unformatted text preview: Chapter 5 Membrane Structure and Function Chapter 4 1 Diffusion of Dye in Water
Dispersing Dynamic Equilibrium Time 0 Time 1 Time 2 Reduced Steep No Concentration Concentration Concentration Gradient Gradient Gradient Solution = Gradient Solute dissolved in Solvent [ ] diff between 2 regions of space Random net movement of molecules from regions high low [ ] Molecules move down gradient No extra energy required Diffusion Faster Diffusion Slow, short distances Higher temp Smaller molecule Greater [ ] gradient Hypertonic Isotonic Hypotonic Osmosis Higher solutes Equal solutes Lower solutes Diffusion of H2O down its gradient across semi permeable membrane H2O moves from hyper soln hypo soln 50% Sugar 1% Starch Osmosis 50% Sugar more hypertonic 1% Starch less hypertonic Both solutions put halffull into dialysis tubing w/semi permeable membrane and soaked in water = hypotonic environment for 45 min The Effects of Osmosis across semipermeable cell membrane
Shriveled RBCs Normal RBCs Swollen RBCs Hypertonic Solution Isotonic Solution Hypotonic Solution Net movement of water out of cells Equal movement of water into and out of cells Net movement of water into cells RBC's: Osmosis Isotonic solution: Hypotonic solution: [ solutes ] + [ free H2O ] outside = inside cell No change in cell volume Extracellular fluid usually isotonic to cytoplasm [ solute ] inside cell > outside cell H2O follows high solutes inside cell Cell gains water [ solute ] outside > inside cell H2O follows high solutes outside cell Cell loses water Hypertonic solution: Hypertonic soln Elodea: Osmosis Hypotonic soln Isotonic soln Phospholipi d Bilayer Brown Recluse Spider venom has lipase that destroys cell membrane Phospholipid Review
Glycerol Fatty Acid
Change from Polar group Triglyceride to Phospholipid Glycerol Fatty Acid Fatty Acid Fatty Acid Fatty Acid Functions of Plasma Membrane 1. 2. 3. Cell = "smallest unit of life" Plasma membrane = "gatekeeper" Isolate inside from outside (phospholipids) Regulate exchange of substances inside/outside cell (proteins) Interact w/other cells + outside (proteins) Selectively Permeable; Semipermeable Fluid Mosaic Model of Membrane
Other Membrane Proteins Enzymes Attachment Connecting Recognition Glycoprotein Receptor Protein Channel Transport Protein H2O, O2, CO2, small lipid solubles pass w/out transport protein Membrane Proteins
Receptor Binds specific molecules (hormones,nutrients) trigger cellular responses Receptor Signal Transduction Video Recognitio Glycoproteins, used by n immune system to tell foreign vs. self HIV glycoproteins Enzymes In/near membrane to promote chemical reactions Attachment Proteins between animal cells DESMOSOME TIGHT JUNCTION Connecting Proteins between cells Connecting Proteins bet GAP JUNCTIONS animals PLASMODESMATA plants Transport Proteins For small hydrophilic (sugars, a.a.) CHANNEL: pores for ions (K+, Na+, Ca2+), H2O GABAA Ion Channel:
allosteric activation by Alcohol, Barbiturates Aquapori n increases Cl flow dampens nerve impulse = sedation Channel Protein Animation CARRIER: binding sites grab specific molecules, change shape & move across membrane Carrier Protein Animation Passive Transport across Membranes
Down gradient No extra energy Simple Diffusion Osmosis = type of simple diffusion Facilitated Diffusion w/transport protein Facilitated Diffusion through a Carrier or Channel protein Against gradient Requires energy: 1 ATP per molecule Active Transport w/carrier protein Pinocytosis Endocytosis Phagocytosis Receptor mediated Exocytosis Energy Requiring Transport across Membranes Pinocytosis cell drinking Phagocytosis cell eating Ameoba engulfs paramecium WBC ingests bacterial Receptormediated Endocytosis to recycle receptors Exocytosis for secretion or expulsion
Secreted Material (extracellular fluid) plasma membrane 2 3 Vesicle
1 (cytoplasm) ...
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