You have discovered an enzyme that can catalyze two different chemical reactions. which of the following is most likely to be correct?
a) the enzyme contains α-helices and β-pleated sheets.
b) the enzyme is subject to competitive inhibition and allosteric regulation.
c) two types of allosteric regulation occur: the binding of one molecule activates the enzyme, while the binding of a different molecule inhibits it.
d) either the enzyme has two distinct active sites or the reactants involved in the two reactions are very similar in size and shape.

The correct option is D.

Enzymes are biological catalysts that speed up the rate of biochemical reactions in living systems by lowering the activation energy required for the reactions to occur. Enzymes take part in various reactions but they are never used up during the course of the reaction.  

Enzymes are very specific in action and will only catalyze certain reactions under optimal conditions. For a single examine to catalyze two different reactions, it implies that the enzyme either have two active sites or the molecules involve in the reaction are very similar in term of size and shape.  

a community that experiences major changes undergoes progress

4.) metal

"-the movement of carbon from the nonliving environment into living things and back to the environment

-carbon is the essential component of proteins, fats, and carbohydrates (which make up all organisms)

-carbon exists in air, water, and living organisms

-producers convert carbon dioxide in the atmosphere into carbohydrates during photosynthesis

-bacteria in the atmosphere cycles through the system in filtration units

-in cellular respiration, carbon is released back into the atmosphere as carbon dioxide

-some carbon is stored in limestone (forming one of the largest "carbon sinks" on earth)

-largest carbon reservoir on earth= limestone

-carbon stored in the bodies of organisms as fat, oils, or other molecules may be released into the soil or air when the organism dies

-this may form deposits of coal, oil, or natural gas (fossil fuels, which increased the atmospheric carbon dioxide)

-fossil fuels store carbon left over from bodies of organisms that died millions of years ago

-they are located in the surface of earth, deep within the earth and beneath the ocean floor."