Sometimes they're used as drugs. The classic example might be penicillin, a compound made by a fungus and used as the first widely-available antibiotic.
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>
Answer:
Enzyme Activity- Responsible reactions Enzyme catalyze nearby substrates
Cell to Cell Recognition- Recognize molecules on surface of the other cells
Cell Signalling- A chemical messenger that binds a membrane protein causing to change shape and relay the message inside a cell.
Transport materials- Provides channels for a certain solutes to pass through membrane
Answer:
the answer is C. the lymph system
