Why is lighter skin an
advantage in places
with less sunlight

How can antibodies "remember" a particular bacterial invader or "antigen" on that invader?

If a cell is placed into a hypertonic environment,what will happen to it ? a)it will shrink or shrivel b)nothing c)it will burst d) it will expand or enlarge

Lactase is essential for digesting lactose in milk. this enzyme is specific for this sugar. why? molecules and active sites vary in size; only properly sized molecules can fit.there is a precise compatibility between the active site and the lactose molecule.specificity refers to the action of the enzyme, such as hydrolysis, and relatively few molecules can be hydrolyzed.reaction-specific enzymes assume a fit by folding around the most numerous substrate molecules.