1. Membranes (start the lab before the notes)
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2. Phospholipid Bilayer
Phospholipids have a 3 carbon backbone with two attached fatty acid chains and a phosphate group
Fatty acid end is nonpolar (water-insoluble)
Phosphate end is polar (water-soluble).
When placed in water, polar ends seek partners for hydrogen bonding, and nonpolar tails pack together.
Lipid bilayer formed.*
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3. Mosaic of proteins float in fluid lipid bilayer.
Fluid Mosaic Model
Mosaic of proteins float in fluid lipid bilayer.
Two layers of phospholipids with proteins embedded
Like jello with fruit floating in it!
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4. Cell Membrane Proteins
Six Major Classes
Transporters-allow certain substances to enter or leave the cell (channels or carriers)
Enzymes-catalyze reactions
Cell Surface Receptors-act like antennae to pick up chemical messages
Cell Surface Identity Markers-allow other cells to identify them (immune system)
Cell Adhesion Proteins-allows cells to glue themselves to other cells
Cytoskeleton Attachments-allow surface proteins to be anchored to the cytoskeleton within the cell
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6. Continues until equilibrium reached.
Diffusion
Random motion causing net movement of substances from regions of high concentration to regions of lower concentration.
Continues until equilibrium reached.
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7. Facilitated Diffusion
Each polar molecule transported across the plasma membrane has its own type of channel.
Selective permeability
Ions move across membrane in ion channels.
Direction of movement determined by relative concentrations and voltage across membrane.
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8. Facilitated Diffusion
Carriers facilitate movement of solutes across membrane by physically binding to them on one side of the membrane and releasing them on the other.
Driven by concentration gradients.
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9. Osmosis
In an aqueous solution, both water and solutes diffuse down a concentration gradient.
Most solutes are not lipid soluble and thus cannot cross membrane.
Water flows through aquaporins (special water channels) in membrane.
Net movement of water across a membrane is called osmosis.
Osmotic Concentration - Concentration of all solutes in a solution.
Hyperosmotic (hypertonic)- Solution with higher concentration.
Hypoosmotic (hypotonic)- Solution with lower concentration.
Isosmotic (isotonic)- Osmotic concentrations of both solutions are the same.
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10. Osmosis
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11. Phagocytosis - Particulate form. Pinocytosis - Liquid form.
Bulk Passage
Endocytosis - Plasma membrane extends outward and envelops food particles.
Phagocytosis - Particulate form.
Pinocytosis - Liquid form.
Exocytosis - Release of material from vesicles at cell surface.
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13. Exocytosis
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14. Requires input of energy.
Active Transport
Moving substances across a membrane against their concentration gradients.
Requires input of energy.
Enables cell to take up additional molecules of a substance already present in its cytoplasm in concentrations higher than in extracellular fluid.
Ex: Sodium-Potassium Pump
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15. Sodium-Potassium Pump
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16. Coupled Transport
Active transport that moves molecules with sodium ions or protons moving down their concentration gradients (Co-transport).
Sodium-potassium or proton pump.
The concentration gradient that is produced by pumping Na+ out can be used to move large molecules inside.
Example: The potential energy of Na+ gradient helps move sugar inside the cell.
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