D. Polarity and size.
<span>The size, polarity, and charge of a substance will determine whether or not the substance can cross the cell membrane by diffusion. The cholesterol was an example of a lipid, and is highly soluble in the nonpolar environment of the lipid bilayer. You saw, in the animation above, the cholesterol freely passing into the hydrophobic environment of the membrane. Cholesterol distributes freely in the membrane and then some fraction will dissolve in the aqueous environment of the cytoplasm. Water, on the other hand, while polar, is small enough to cross the membrane at a slow rate. Note that specialized transport proteins in certain cell membranes can provide a channel for the water, greatly increasing its rate of crossing the membrane. The lipid bilayer is much less permeable to the ion, because of its charge and larger size. As a general rule, charged molecules are much less permeable to the lipid bilayer.</span>
James B. Connolly of Massachusetts was the first modern Olympic champion to be rewarded with a silver medal. He represented the Suffolk Athletic Club
Answer:
C. Reactant and product concentrations in the test tube are different from those in the cell.
Explanation:
Cells convert some of the energy from ATP hydrolysis in to different forms of energy other than heat. ATP energy does not always generate more heat. Many times, energy is used for different purposes.
Answer:
C. "Using the sodium-potassium pump involves the hydrolysis of ATP and the
release of Nat to the outside of the cell."
Explanation:
The use of a sodium-potassium pump is a form of active transport, not diffusion. It also requires energy because the pump moves ions against their concentration gradient (low to high), unlike diffusion.
