Which of the following explains why most elements in the periodic table have a decimal number for their atomic mass?
a. most elements have different isotopes.
b. most elements have different number of electrons.
c. most elements have different numbers of protons in the nucleus.
d. most elements are not found in nature.

1. an enzyme is considered a(n) because it speeds up a chemical reaction without being used up.2. in a catalyzed reaction, a reactant is often called a(n) . an enzyme is specific because the shape of its matches only particular reactants.4. an enzyme speeds up reactions by lowering the . the between an active site and its substrate often strains bonds and the reaction proceed.6. a( , which is often a vitamin, binds to an enzyme and plays a role in catalysis.7. high temperatures or changes in ph can an enzyme, causing it to lose its shape and biological activity.

Which of the following is a heterotroph?

1. disease can be caused by viruses, bacteria, fungi, parasites, or toxic chemicals. which of these diseases is the result of toxic chemicals?