TRANSPORT ACROSS THE CELL MEMBRANE
THE FLUID MOSAIC MODEL
PROPERTIES OF MEMBRANE:
- "Phospholipids" grout and "Proteins" tiles
- Pliable (vesicles bud off and fuse)
- Phospholipid Bi-layer has a certain fluidity
- Asymmetrical (Phospholipids vertically face opposite directions of the membrane)
STRUCTURAL COMPONENTS:
- PHOSPHOLIPIDS: main structural component, isolates cell cytoplasm from exterior, hydrophillic (head region) faces intracellular and extracellular fluids, hydrophobic (tail region) face eachother, allows and restricts molecules from enetering/exiting the cell
- CHOLESTEROL: lipid embedded within membrane, makes bilayer stronger, more flexible, and less fluid, hydrophobic nature restricts water soluble molecules from penetrating the membrane
- GLYCOLIPIDS: phospholipids attached with a carbohydrate (straight or branched glucose sugar chains); provide cell with a specific recognition/ID marker to help prevent against certain diseases, illnesses, etc. from recurring
PROTEINS:
TWO MAIN TYPES:
1. Integral--> Embedded within bilayer, hydrophobic regions embedded in membrane, hydrophillic regions extending from the bilayer
2. Peripheral--> Attached to the surface of membrane, held by protein filaments or free drifting laterally [MOSAIC]
- RECEPTOR: has a distinct binding site, molecular triggers that set off cell responses w/ specific molecules in extracellular fluid [Integral]
- GLYCOPROTEINS: proteins with an attached carbohydrate chain that projects externally from the membrane; ID/recognition markers [like glycolipids], cell surface attachment sites {Peripheral}
- TRANSPORT: regulate movement of water-soluble molecules through the membrane; Channel: form pores that allow smaller water-soluble molecules to penetrate the membrane & Carrier: have binding sites, require ATP energy to help move larger molecules across the membrane [Active Transport, Endo and Exocytosis] [Integral]
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