nucleic acids Flashcards
1
Q
what elements do nucleic acids contain
A
carbon
hydrogen
oxygen
nitrogen
phosphorus
2
Q
monomers of nucleic acids
A
nucleotides
3
Q
what is a nucleotide made up of
A
- pentose monosaccharide (5 C atoms)
- phosphate group -PO42- (Inorganic, acidic, negatively charged)
- nitrogenous base (organic molecule, 1 or 2 C rings and nitrogen)
4
Q
how are nucleotides linked together
A
- phosphodiester bonds in condensation reactions to form polynucleotides.
- 5’ carbon on the pentose sugar on a nucleotide forms a covalent bond with the OH group of the 3’ carbon on the pentose sugar on an adjacent nucleotide.
- forms a long, strong sugar-phosphate backbone with a base attached to each sugar
5
Q
Pyramidines
A
- the smaller bases
- thymine, cytosine
- single carbon ring structures
6
Q
purines
A
- the larger bases
- adenine, guanine
- double ring structures
7
Q
difference between DNA and RNA
A
- DNA contains deoxyribose sugar
- RNA contains ribose sugar
- deoxyribose has 1 less oxygen atom than ribose
8
Q
what structure is DNA found in
A
double helix
9
Q
why are the 2 strands of DNA said to be antiparallel
A
- they run parallel to each other but in opposite directions
- Each strand has a phosphate group (5’) at one end and a hydroxyl group (3’) at the other end.
10
Q
complementary base pairing
A
- adenine pairs with thymine with 2 hydrogen bonds
- cytosine pairs with guanine with 3 hydrogen bonds
11
Q
how is a constant distance maintained between DNA strands
A
- complementary base pairing means that a small pyrimidine base is always paired with a large purine base
- constant distance between backbones is contained
- so polynucleotides are parallel
12
Q
why is RNA shorter than DNA
A
- the relatively short section of the long DNA molecule corresponding to a single gene is transcribed into a similarly short mRNA molecule.
- so each individual mRNA is shorter than the whole chromosome of DNA
13
Q
RNA nucleotide
A
- pentose sugar ribose
- thymine base is replaced with uracil
- uracil is a pyrimidine that forms 2 hydrogen bonds with adenine
14
Q
how do RNA nucleotides form polymers
A
- formation of phosphodiester bonds in condensation reactions (Same as DNA)
15
Q
why can RNA leave the nucleus
A
- RNA polymers are small enough to leave via nuclear pores and travel to the ribosomes through cytoplasm