Scientists believe that macromolecules could have been formed before there were living cells by
a. chemical processes removing water from components.
b. oxidation of compounds containing phosphate.
c. lightning discharge catalyzing addition of water to molecules.
d. enzyme-mediated condensation reactions.
e. acidic hydrolysis of compounds in the Earth's oceans.
A; Biological macromolecules are formed by dehydration condensation, a process that removes a water molecule from between two subunits. Today this is done enzymatically, but prior to the evolution of living systems there were no specific enzymes (choice d). Choices b, c, and e would all tend to break up macromolecules, not synthesize them.
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A. oxygen. B. nitrate. C. NAD. D. an inorganic molecule. E. oxygen, nitrate, AND an inorganic molecule.
Enzymes speed chemical reactions by ________ the reaction
a. lowering the activation energy of b. being destroyed by c. providing energy to d. changing the ratio of energy of reactants to energy of products in
In the final stage of SCNT, a(n) _____ is used to cause the foreign cell to fuse with, and empty its contents into, the
cytoplasm of the egg.
a. fine point needle b. virus c. micropipette d. electric current e. calcium phosphate
Children who are pituitary dwarfs can now grow to normal height because of
A) large supplies of growth hormone from dead animals. B) the invention of synthetic growth hormone. C) genetic repair before birth. D) genetically engineered production of growth hormone by bacteria. E) pituitary transplants.