Nucleic Acids Flashcards
what are nucleic acids?
large molecules that were discovered in cell nuclei.
what are the two types of nucleic acid?
- DNA
- RNA
what are the roles of nucelic acids?
- roles in storage
- roles in transfer of genetic information
- roles in the synthesis of polypeptides
- they are the basis for heredity.
what elements do nucleic acids contain?
carbon, hydrogen, oxygen, nitrogen, and phosphorus.
which monomers form nucleic acids?
nucleotides - linked together in a chain.
what are the three components that make up a nucleotide?
- a pentose monosaccharide, containing five carbon atoms.
- a phosphate group
- a nitrogenous base.
what is a phosphate group?
an inorganic molecule that is acidic and negatively charged.
what is a nitrogenous base?
a complex organic molecule containing one or two carbon rings in its structure as well as a nitrogen.
what type of reaction links nucleotides together?
condensation reaction to form a polymer called a polynucleotide.
how is a long sugar phosphate backbone formed?
the phosphate group at the fifth carbon of the pentose sugar of one nucleotide forms a covalent bond with the hydroxyl group at the third carbon of the pentose sugar of an adjacent nucelotide. The bonds are called phosphodiester bonds.
what type of reaction breaks the phosphodiester bonds to release individual nucleotides?
hydrolysis reaction.
what does DNA stand for?
Deoxyribonucleic acid.
what is the sugar in DNA?
deoxyribose.
what is deoxyribose?
a sugar with one fewer oxygen atoms than ribose.
what are the four different DNA nucleotides?
- thymine
- cytosine
- adenine
- guanine
what are the two groups that DNA nucelotides can be split into?
- pyrimadines
- purines
what are pryimadines?
the smaller bases, which contain single carbon ring structures - thymine and cytosine.
what are purines?
the larger bases, which contain double carbon ring structures - adenine and guanine.
do purines pair with pyrimadines?
yes.
how many hydrogen bonds does thymine and adenine form?
two.
how many hydrogen bonds does cytosine and guanine form?
three.
how long is a DNA molecule?
it varies in length from a few nucleotides to millions of nucleotides.
what forms the DNA double helix?
two strands of polynucleotides coiled into a helix.
what holds the two strands of the double helix together?
hydrogen bonds between bases.
what is the structure of the strands of the double helix?
they have a phosphate group (5’) at one end and a hydroxyl group (3’) at the other.
why are strands described as antiparallel?
the two parallel strands are arranged so that they run in opposite directions.
what does the pairing between bases allow DNA to do?
be copied and transcribed - key properties required of the molecule of heredity.
what is complementary base pairing?
the idea that A and T always join with each other, and C and G always join together.
what causes parallel polynucleotide chains?
a small pyrimidine base always binds to a larger purine base. this arrangement maintains a constant distance between the DNA ‘backbones’, resulting in parallel polynucelotide chains.
does DNA have equal amounts of adenine and tymine, and equal amounts of cytosine and guanine.
yes.
what is the role of RNA?
plays an essential role in the trasfer of genetic information from DNA to the proteins that make up the enzymes and tissues of the body.
how can DNA leave the nucleus?
relatively short section of the long DNA molecule corresponding to a single gene is transcribed into a similarly short mRNA molecule; each individual mRNA is shorter than the whole chromosome of DNA
how are RNA nucleotides different to DNA nucleotides?
- pentose sugar is ribose rather than deoxyribose.
- thymine base is replaced with the base uracil.
how do RNA nucleotides form polymers?
the formation of phosphodiester bonds in a condensation reaction.
what happens after protein synthesis?
RNA molecules are degraded in the cytoplasm. phosphodiester bonds are hydrolysed and RNA nucleotides are released and reused.
how can DNA be extracted?
- grind a sample in a mortal and pestle to break down the cell walls.
- mix the sample with detergent - this breaks down the cell membrane and releases cell contents into solution.
- add salt - breaks hydrogen bonds between DNA and water molecules.
- add protease enzyme - breaks down proteins associated with DNA in the nuclei.
- add a layer of ethanol on top of the sample - alcohol causes the DNA to precipitate out of solution.
- the DNA will be seen as white strands forming between the layer of sample and layer of alcohol. The DNa can be picked up by spooling it onto a glass rod.
