Lecture 6: Nucleotides and Nucleic Acids Flashcards
what is DNA?
hereditary material in almost all organisms
what is the function of DNA?
storage of genetic information for protein synthesis
RNA is involved in the expression of genetic material through transcription by ___RNA and translation by __RNA and __ RNA
M and R
a variety of small RNA molecules play a regulatory roles in ___ in the cell
gene expession
all cellular lifeforms on earth use __ to store genetic information, but some viruses use ___ instead
DNA; RNA
what are the building blocks of DNA and RNA?
nucleotides
all nucleotides are composed of what three components?
- nitrogenous base
- five-carbon sugar
- phosphate group
the ___ uniquely characterizes a nucleic acid and is a form of information
sequence of bases
nitrogenous bases are derivatives of either __ or __
pyrimidine or purine
the rings in both pyrimidines and purines are referred to as __, meaning they contain elements in addition to carbon
heterocycles
the ring structure of purines is the fusion of what two rings?
pyrimidine and imidazole rings
RNA and DNA have the same bases, except that RNA contains __- instead of thymine
uracil
purines have ___ heterocycles
2
pyrimidines have ___ heterocycles
1
which nucleotides are purines?
adenine and guanine
which nucleotides are pyrimidines?
thymine, uracil, cytosine
what toxic compound is found in chocolate, tea, and cola (why dogs cant have it)?
theobromine
adenosine is a component of ___ and therefore involved in energy and many biochemical functions
ATP
give 6 examples of biochemical (physiological) roles of adenosine in the body
- hormonal functions
- blood vessel dialation
- smooth muscle contraction
- neurotransmitter release
- metabolism of fat
- regulates sleep/wake
upon long periods of wakefulness, adenosine levels __ and promote sleepiness by interacting with __ receptors
rise; neuron
caffeine is a structural mimic of ___ and blocks the receptors and function (making you less sleepy)
adenosine
nitrogenous bases are relatively ___ (hydrophilic or hydrophobic)
hydrophobic
because of their aromaticity, nitrogenous bases absorb UV radiation at ___nm very strongly
260
the planar shape of nitrogenous bases allows them to participate in __ interactions with other aromatic groups, like side chains on certain amino acids
stacking
what are nucleosides?
nitrogenous base covalently joined to a 5C sugar (ribose)
nucleotides are nucleosides with ___ group on the 5’C of the sugar
phosphate
multiple phosphate groups can be linked by ___
phosphoanhydride linkages
ATP is an energy carrier and provides energy due to the energy carried in its ___
anhydride bonds
a polynucleotide chain has individuality determined by the __
sequence of bases
in nucleic acids, the ribose of each nucleotide is joined by a ___ bond
phosphodiester
a phosphodiester bond is a ___ group covalently attached to the C5’ ___ of one sugar and the C3’ ___ of another sugar
hydroxyl x2
molecules begin with the ___ phosphate and end with the __ hydroxyl group (5’/3’)
5’; 3’
what is the directionality of nucleic acids?
5’-3’
nitrogenous bases have groups that can participate in H bonding (t/f)
true
hydrogen bonding is important for (2)
- double stranded DNA structure
2. interaction with DNA binding proteins
pyrimidines and purines only pair with one another (1 pyrimidine and 1 purine) (t/f)
true
the bottom strand directionality is ___ to the top strand
anti-parallel
a gene is nothing more than a ___
DNA sequence
the double helix structure of DNA forms spontaneously in water (t/f)
true
the double helix of DNA is stabilized by three major interaction types
- hydrogen bonding
- hydrophobic affect
- stacking interactions
hydrogen binding occurs between ___ of DNA
bases of complementary strands
the hydrophobic effect causes nitrogenous bases of DNA helix to be ___
shielded from contact with water
which structure of the DNA molecule is more hydrophilic?
sugar-phosphate backbone
stacking interactions occur between __ of DNA
bases on the same strand
stacked bases interact with each other through ___ between adjacent planar bases
van der waals forces
describe how the hydrophobic effect affects the creation of the double helix shape of DNA
adopts a twisted structure to shield hydrophobic molecules from water
each adjacent bases pair is separated by a distance that is ideal for the formation of
van der waals forces
what causes the DNA helix to have major and minor grooves?
the 2 glycosidic bonds are not diametrically opposite each other
in the DNA helix, each base pair has a larger and smaller side which define the ___
major and minor grooves
proteins essential to transcription and translation typically bind to DNA at the __
major groove
how does a protein bind to the DNA double helix?
functional groups on the amino acid side-chains interact with the functional groups of the nitrogenous bases in the major groove
the major groove is lined with potential H-bond __
acceptors
the minor groove is lined with potential H-bond __
donnors
3 reasons why the major groove is the primary site of specific interaction by DNA binding proteins
- fits a protein structure
- more information exposed
- more diversity in pattern of molecular interaction sites
