S/A Nucleotides & NA Flashcards
How are a nucleoside and a nucleotide similar and how are they different?
Both have a nitrogenous base and a pentose; nucleotides also have a phosphate group, which nucleosides lack.
Compounds that contain a nitrogenous base, a sugar, and a phosphate group are called (a)_________________. Two purines found in DNA are (b)______________ and __________________. A pyrimidine found in all DNA but in only some RNA is (c)_________________. In DNA, the base pair (d)___-___ is held together by three hydrogen bonds; the base pair (e)___-___ has only two such bonds.
ns: (a) nucleotides; (b) adenine and guanine; (c) thymidine; (d) G–C; (e) A–T
Describe briefly what is meant by saying that two DNA strands are complementary.
The nucleotide sequences of complementary strands are such that wherever an A occurs in one strand, there is a T in the other strand with which it can form a hydrogen-bonded base pair. Wherever a C occurs in one strand, a G occurs in the other. A is the base complementary to T, and C is the base complementary to G.
xplain how nucleoside triphosphates (such as ATP) act as carriers of chemical energy.
In these molecules, there is a phosphoric anhydride linkage between the phosphates. Hydrolysis of this linkage (i.e., of ATP to ADP and phosphate) is a highly exergonic reaction that results in the release of a large amount of free energy. Conversely, the input of a large amount of free energy is required for the synthesis of the linkage; i.e., for the phosphorylation of ADP to form ATP. Thus, synthesis of ATP results in the storage of energy that can be released upon hydrolysis.
