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BIO 161 CH. 6

Terms in this set (21)

What structural features do all lipids have in common?
hydrocarbons, reduced carbons (high energy storage), non polar parts
what distinguishes hydrophilic molecules from hydrophobic molecules?
Hydrophilic: polar, electronegative difference, interact with water, soluble
Hydrophobic: nonpolar, equal electronegativity, does not interact with water, insoluble
of the major macromolecules, which are hydrophilic and which are hydrophobic?
carbohydrates, some amino acids and nucleic acids are hydrophilic
lipids and some amino acids are hydrophobic
what is an amphipathic molecule?
the molecule can divide in half with a non polar tail and a polar head in a lipid
What characteristics shared by polypeptides, nucleic acids and polysaccharides are NOT characteristic of lipids?
There are no polymers formed by monomers in lipids

other macromolecules are formed through condensation reactions, but lipids are formed through dehydration reactions
Explain how the presence of C=C double bonds in the fatty acids of phospholipids alters membrane properties.
Double bonds in unsaturated hydrocarbon tails create kinks, and spaces among the tails. This reduces strength of van der Waals interactions and weakens the barrier to solutes. Allows some molecules to leak through. More fluid.

Saturated tails without double bonds have fewer spaces and can pack more densely, and have stronger VdW forces. Less permeable membranes. Less fluid.
what is the difference between diffusion and osmosis?
Diffusion: the movement of solute molecules from low to high concentration along gradient
Osmosis: movement of water along semi-permeable membrane from low to high concentration
Explain "selective permeability" and give examples of molecules that can/can't cross membranes.
Some molecules can go through easily, others more slowly, if at all.
- Permeable: nonpolar, steroids, small molecules (O2, CO2, H2O)
- Cannot cross: charged/polar, macromolecules, integral proteins
What evidence supports the idea that CFTR is a channel?
Researches purified CFTR and measured electric currents across the membrane. Ions carry charge so if they move across membrane, a current would be present. No CFTR channel = no electric current through membrane. Evidence suggest CFTR is a Cl ion channel.
Compare and contrast carrier proteins with channel proteins
Compare and contrast carrier proteins with channel proteins Carrier proteins: membrane proteins that change shape during the transport process. Powered by diffusion. Passive. Binds molecule then changes shape.

Channel proteins: structured for specific molecules to pass through, very selective. Passive. Depends on gradient/concentration.
Describe passive transport
powered by diffusion (random movement) along electrochemical gradient.
How does the concentration of K+ and Na+ differ between the cytoplasm and the external environment? How is this gradient maintained?
- sodium ions from inside bind to the site and are released to outside the cell
- phosphate group from ATP transferred to the pump
- conformation changes and potassium now binds to the site from the outside, moving to the interior of the cell.
Why does soap (a detergent) kill bacteria?
Soap is a detergent, a small amphipathic molecule that tends to form micelles in water. Micelles have polar heads and nonpolar tails that are able to isolate bacteria.
Clearly articulate the difference between a carrier protein and a pump protein.
Carriers undergo conformational changes that facilitate the diffusion of specific molecules into/out of the cell.

Pumps use energy to actively move ions or molecules in a single direction, often times against the gradient.
Why does active transport require an energy source?
Moves against gradient and requires energy to counteract the decrease in entropy that occurs when molecules/ions are concentrated. Provided by phosphate group from ATP.
What are the characteristics of the integral membrane protein?
Amphipathic and contain amino acids that have side chains that are both nonpolar and polar. Integral protein have segments that face the interior and exterior of the cell so can use these AA to make itself hydrophobic or hydrophilic depending on the environment. Fluid mosaic model supports that the structure of the phospholipid bilayer is dynamic and fluid, therefore integral proteins must be able to change conformation.
In addition to phospholipids, what other biologically important molecules are classified as lipids? What properties of these molecules make it appropriate to classify them as lipids?
Steroids, and fats. Made of hydrocarbons. Insoluble in water. Amphipathic.
describe why oil and water do not mix.
Oil is a hydrophobic, non-polar molecule made up of chains of hydrocarbons.
Water is a polar molecule and in order for the two to interact, oil would need a charge. Therefore the two are unable to mix together.
How can proteins in the plasma membrane affect the osmotic balance in a cell?
there are many important molecules (ions, glucose, etc.) that MUST cross the membrane but can't. integral membrane proteins are what make it possible for molecules like that to cross through facilitated diffusion. In terms of active transport there are very steep gradients of Na+ and K+ across the membrane of most cells. These ions can't cross themselves so proteins in the membranes have to move them across to create the gradients.
While lipids do not conform to the typical monomer/polymer relationship common to the other macromolecules, some do undergo condensation reactions. Explain.
Phospholipids are made through condensation reactions. When the tails are added to the head, an H2O is lost.
Start with three carbons bound together (-C-C-C-). What individual atoms or functional groups could you add to the carbons to make the molecule hydrophobic? Hydrophilic?
Add H's to make hydrophobic. Add Phosphate (polar O's) or OH to make it hydrophilic
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