150 Study Guide 2 Fall 2017.docx

150 Study Guide 2 Fall 2017.docx - 150 Study Guide 2 Fall...

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150 Study Guide 2 Fall 2017 1. Know the general features of the Fluid Mosaic model of membrane structure. Fluid (can move) Mosaic (made up of a lot of different parts integrated together) Bilayer (helps regulate what goes in and out) Proteins (serve as markers on the surface for identification purposes and to allow certain molecules in and out) Transport (passive and active, allows molecules across membrane) 2. How do integral and peripheral membrane proteins differ? Integral membrane proteins are partly embedded in the phospholipid bilayer . Peripheral membrane proteins lack hydrophobic groups and are not embedded in the bilayer. 3. What factors influence the fluidity of membranes? 1. Lipid composition - types of hydrocarbon tails (unsaturated or saturdated) can increase or decrease fluidity. 2. Temperature - membrane fluidity decreases in colder conditions 4. What is meant by “semi-permeable” (or “selectively permeable”)? Biological membranes allow some substances , and not others, to pass. 5. What types of molecules move across membranes most easily? Small membranes move across membranes most easily In simple diffusion: o A molecule that is hydrophobic and soluble in lipids can pass through the membrane. o Polar molecules do not pass through the- they are not soluble in the hydrophilic interior of the membrane. 6. The phospholipid bilayer is impermeable to what types of molecules? How are such molecules moved across membranes? Phospholipids form a bilayer which is like a “lake” in which a variety of proteins “float. Ions and large polar molecules cannot pass through the lipid bilayer . But more specifically, whether a molecule can pass through the membrane depends on its size and its electrical nature. The membrane is highly permeable to non-polar (fat-soluble) molecules 7. What is the difference between passive transport and active transport? Passive transport: does not require metabolic energy Active transport: requires input of metabolic energy. 8. What type of membrane transport always requires energy? Active transport: requires input of metabolic energy.
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9. With reference to membranes, what is a concentration gradient? The concentration gradient refers to the gradual change in the concentration of solutes present in a solution between two regions. A gradient, results from an unequal distribution of ions across the cell membrane. When this happens, solutes move along a concentration gradient. This kind of movement is called diffusion. o Diffusion refers to the net movement of molecules from higher to lower concentration, and may be classified as simple or facilitated.
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