Adenine base pairs with thymine using bonds, and guanine base pairs with cytosine using bonds. three hydrogen, two hydrogen
two hydrogen, three hydrogen
three phosphoester, two phosphoester
two phosphoester, three phosphoester

The model illustrates a process by which a substance is taken up by a cell

Animal bodies (and even plant bodies for that matter) are complex enough that life couldn't exist without enzymes. enzymes are usually large, complex biological catalysts that are expensive to make. enzymes speed up the rate of chemical reactions without being used up during the reaction (they can be reused many times). they are highly specific in the reactions they regulate. knowing what enzymes are and how they function, why does this explain why complex life forms could not exist if there were no enzymes.

Some tools have graduations to show multiple measurements. for example, a ruler may have graduations for both millimeters and centimeters. when measuring the length of an earthworm, which graduations would allow for the most accurate measurement? millimeters centimeters decimeters meters