Chapter 7 Membranes
Lipids that form membranes have what kind of structure?
Polar heads and nonpolar tails; the polar heads interact with water
a membrane protein that spans the phospholipid bilayer one or more times is
a transmembrane protein
For a protein to be an integral membrane protein, it would have to be
amphipathic, with at least one hydrophobic region
which of the following allows water to move much faster across cell membrane
aquaporins
a cell that neither gains nor loses water when it is immersed in a solution is
isotonic to its enviroment
which of the following crosses lipid bilayers the fastest
a small, nonpolar molecule like oxygen
Osmosis can be defined as
the diffusion of water
If placed in tap water, an animal cell will undergo lysis, whereas a plant cell will not. What accounts for this difference?
The relative inelasticity and strength of the plant cell wall
the presence of cholesterol in the plasma membranes of some animal cells
enables the membranes to stay fluid when cell temperature drops.
Glucose diffuses slowly through artificial phospholipid bilayers. The cells lining the small intestine, however, rapidly move large quantities of glucose from the glucose-rich food into their glucose-poor cytoplasm. Using this information, which transport mechanism is most probably functioning in the intestinal cells?
facilitated diffusion
In the lab, you use a special balloon that is permeable to water but not sucrose to make an "artificial cell." The balloon is filled with a solution of 20% sucrose and 80% water and is immersed in a beaker containing a solution of 40% sucrose and 60% water. The balloon is____ relative to the solution in the beaker.
hypotonic
Celery stalks are immersed in fresh water for several hours become stiff. Similar stalks like this we can deduce that the fresh water
is hypotonic and the salt solution is hypotonic to the cells of the celery stalks
Some protozoans have special organelles called contractile vacuoles that continually eliminate excess water from the cell. The presence of these organelles tells you that the environment
is hypotonic to the protozoan
a plant cell in a hypotonic solution
is turgid
A phospholipid is a
nonpolar lipid molecule that is made amphipathic by the addition of a phosphate
Diffusion does not require the cell to expend ATP. Therefore, diffusion is considered a type of
passive transport
Which of the following types of molecules are the major structural components of the cell membrane
phospholipids and proteins
why are lipids and proteins free to move laterally in membrane
there are only weak hydrophobic interactions in the interior of the membrane
under what circumstance does membrane transport require energy
whenever a solute is moved against its concentration gradient.
You are adrift in the Atlantic Ocean, and, being thirsty, drink the surrounding seawater. As a result,
you dehydrate yourself