Chapter seven: membrane structure and function

There are integral protein and peripheral protein in this graph which is known as mosaic proteins. They help select substances and tranport them. The hydrophobic part of protein is inside the lipids.


Main questions:
1.In what way do the membranes of a eukaryotic cell vary?
A: Certain proteins are unique to each memebrane.
2.What does passive transport includes?
A: osmosis, diffusion of a solute across a membrane, facilitated diffusion, transport of an ion down its electrochemical gradient.
3.What experimental treatment would increase the rate of sucrose transport into the cell?
A: decreasing extracellular pH.

Main facts:
1.Amphipathic proteins are embedded in the phospholipid bilayer.
2.Short chains of sugars are linked to proteins and lipids on the exterior side of the plasma membrane, where they interact with surface molecules of other cells.
3.Membrane proteins and lipids are synthesized in the ER and modified in the ER and Golgi apparatus. The inside and outside faces of the membrane differ in molecular composition.
4.Diffusion is the spontaneous movement of a substance down its concetration gradient.
5.In facilitated diffusion, a transport protein speeds the movement of water or a solute across a membrane down its concentration gradient.

Summary:
Cell membrane not only provides protection but also transportation. Cell memebrane contains proteins, carbohydrate, glycolipid and cholesterol. Passive transport is diffusion of a substance across a memebrane with no energy investment. This chapter is basically talking about the function how proteins transport molecules from outside of cell till inside.
If there is no cell membrane which is just like a house without door. Anything could get into cell without guarding. Which cell membrane is very important to the cell.


Key terms:
1. Concentration gradient: A region along which the density of a chemical substance increases or decreases
2. Receptor: mediated endocytosis-The movement of specific molecules into a cell by the inward budding of membranous vesicles containing proteins with receptor sites specific to the molecules being taken in; enables a cell to acquire bulk quantities of specific substances.
3. Amphipathic: having both a hydrophilic region and a hydrophobic region.
4. Fluid mosaic model: The currently accepted model of cell membrane structure, which envisions the membrane as a mosaic of protein molecules drifting laterally in a fluid bilayer of phospholipids.
5. Integral proteins: Typically a transmembrane protein with hydrophobic regions that extend into and often completely span the hydrophobic interior of the membrane and with hydrophilic regions in contact with the aqueous solution on either side of the membrane.
6. Peripheral proteins: A protein loosely bound to the surface of a membrane or to part of an integral protein and not embedded in the lipid bilayer.
7. Glycolipids: A lipid with covalently attached carbohydrate.
8. transport proteins: A transmembrane protein that helps a certain substance or class of closely related substances to cross the membrane.
9. Electrogenic pump: An ion transport protein that generates voltage across a membrane.
10. Passive transport: The diffusion of a substance across a biological membrane with no expenditure of energy.

Video: http://www.youtube.com/watch?v=STzOiRqzzL4&feature=related