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