Why do the capillaries have to be so small?

Some substances but not other can cross the (blank) membrane of a cell

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.

When does an organism become an adult during a life cycle? a)before metamorphosis is complete b)after producing offspring c)after development is complete d)before gametes fuse