Ch. 14: Lipids Flashcards
What is a phospholipid?
A nonpolar lipid molecule that is made amphipathic by the addition of a phosphate
What will happen to a red blood cell, which has an internal ion concentration of about 0.9 percent, if it is placed into a beaker of pure water?
The cell will swell and may burst because pure water is hypotonic (there are no ions in the water, therefore through osmosis the water will move into the cell to try to reach a state of equilibrium)
If cells do not change size, what does this say about osmosis?
It did not occur
What kind of molecules can cross the phospholipid bilayer?
- -Hydrophobic (non-polar) molecules (fatty acids, etc.)
- -Gases
- -Small, uncharged molecules (even polar molecules can cross if they are small enough, like water)
If a cell is starved of glucose for 12 hours, and the glucose transporters are blocked (remember glucose is too large to move across the membrane by itself), and then glucose is added to the solution with the cell, what will happen to the cell?
Water will move out of the cell via osmosis and cause the cell to shrivel
Place 200mM chloroform in chamber 1 and 30 mM NaCl in chamber 2. After equilibrium is reached how do the water levels compare? How do the relative chloroform and NaCl concentrations compare?
Chamber 2 will have a higher water level, whereas the chloroform concentration will be the same. NaCl will be higher in chamber 2
What is the endomembrane system and what organelles ARE NOT part of it?
- -The set of membranes that form a single functional and developmental unit, either being connected directly, or exchanging material through vesicle transport.
- -Importantly, the endomembrane system does not include the membranes of mitochondria and chloroplasts.
Where are proteins for export made?
The Rough ER
What characteristic of ATP are responsible for its high energy level?
The potential energy associated with ATP is held by the covalent bonds between the phosphate groups, particularly the high-energy bond between the second and third phosphate groups.
Under what circumstances does membrane transport ALWAYS require energy?
Whenever moving a solute AGAINST its concentration gradient
What is the best explanation for why cholesterol decreases permeability of biological membranes?
Because cholesterol is amphipathic, it fits in between the phospholipids and blocks diffusion through the membrane.
What determines if a fat is a liquid or solid at room temperature?
The more double bonds a hydrocarbon has, the less saturated it becomes. This prevents it from interacting hydrophobically with other unsaturated chains as much, thus decreasing its melting point
Which is less viscous, polyunsaturated lipids or saturated lipids?
Polyunsaturated lipids (those with several double bonds) are less viscous than are saturated lipids.
What is the second law of thermodynamics?
The entropy of a closed system always increases
Why does diffusion occur spontaneously?
Because it results in an increase in entropy
