PORTAGE BIOCHEM MODULE 6
What is the difference between a nucleoside and nucleotide? - Answer - A nucleoside
is formed from the covalent bonding of a base (purine or pyrimidine) to either ribose
(RNA) or 2-deoxyribose (DNA). Nucleotides are built from a nitrogen-containing organic
base, a monosaccharide, and phosphate.
What characteristic makes purines and pyrimidine heterocyclic? - Answer - Each has a
ring with nitrogen in the ring instead of all carbon atoms in the ring.
Is this molecule ribose or 2-deoxyribose? Briefly explain what structural information was
used to determine this. - Answer - Ribose. This molecule contains an -OH on carbon 2.
2-deoxyribose has an -H atom on the second carbon.
Is the following a pyrimidine or purine? Provide the name and one-letter symbol. -
Answer - Pyrimidine. It is thymine (T).
What is the difference between thymine and uracil? - Answer - These two bases differ
by a methyl group. Thymine has an extra methyl group on the ring.
From the course and module information, where in a eukaryotic or prokaryotic cell, is
the DNA located? How about the RNA? - Answer - DNA is located in the nucleus of a
eukaryotic cell or the nucleoid of a prokaryotic cell. RNA is found in the nucleus, on the
ribosome, and in other parts of the cell.
Which DNA and RNA bases contain a carbonyl group? - Answer - Guanine, cytosine,
thymine, and uracil all contain C=O group attached to the rings. Adenine is the only
base that does not.
What constitutes the backbone of DNA? - Answer - In DNA, this consists of the
alternating deoxyribose and phosphate groups linked together through covalent bonds.
