Membranes and Transport seven and eight

Membranes and Transport seven and eight - Membranes and...

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Membranes and Transport – Key Concepts A hallmark of living cells is their ability to . .. what? How do they do this? Their ability to regulate the substances that enter and leave them. They do this by forming a barrier and doing a group of proteins that act as a carrier to get things across the membrane. Describe CF and motor neuron disease; what do they have in common? CF lacks Cl- ion channels and cannot regulate to let the water out which loosens the mucus. MND also has a problem with channels opening. What are the three classes of macromolecules that make up membranes? Lipids, carbohydrates, and proteins. Explain the "fluid mosaic model." The fluid mosaic model shows the lipid bilayer with proteins and carbohydrates attached and in constantly moving and flowing. Some of the proteins adhere one cell to another. Some integral proteins do not go all the way through the lipid bilayer. Some peripheral proteins do not penetrate the bilayer at all. Cholesterol is in the “tails” or the inside part of the membrane, and help keep the cell stiff, too much is a bad thing. Carbohydrates are located outside the membrane on the outer surface of proteins. What is it about phospholipids that enables them to form the barriers necessary to regulate cell contents? The hydrophilic heads and hydrophobic tails. Nothing that is hydrophilic can get through the membrane due to the hydrophobic tails, and since most things are hydrophilic, this blocks many substances from getting in or out without using channels which help to regulate hydrophilic substances. Phospholipids are amphipathic have both polar and nonpolar regions, the polar heads can freely associate with water or the many polar solutes inside and around cells; the lipid tails are repelled by water and polar molecules. Phospholipids spontaneously form bilayers, with polar heads facing out into aqueous solutions and nonpolar tails facing into the center of the membrane; the nonpolar regions block the simple diffusion of those polar substances across the membrane; small nonpolar molecules can diffuse freelyPolar molecules get past the barrier through channel or carrier proteins that cross the membrane Proteins that are embedded in and cross the plasma membrane must have regions that are hydrophilic and others that are hydrophobic. Where must each region be located, and why? The hydrophilic parts of proteins must be near the heads of the plasma membrane, while the hydrophobic parts of proteins must be near the tails. This is because if a hydrophobic and hydrophilic part were close to each other, they would push each other away therefore not forming a good barrier. What functions do carbohydrates play in membranes? The immune system and in cell recognition (telling good cells from bad cells).
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Membranes and Transport seven and eight - Membranes and...

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