nucleic acids

Question 1

what elements do nucleic acids contain

Answer 1

carbon
hydrogen
oxygen
nitrogen
phosphorus

Question 2

monomers of nucleic acids

Answer 2

nucleotides

Question 3

what is a nucleotide made up of

Answer 3

• pentose monosaccharide (5 C atoms)
• phosphate group -PO42- (Inorganic, acidic, negatively charged)
• nitrogenous base (organic molecule, 1 or 2 C rings and nitrogen)

Question 4

how are nucleotides linked together

Answer 4

• 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

Question 5

Pyramidines

Answer 5

• the smaller bases
• thymine, cytosine
• single carbon ring structures

Question 6

purines

Answer 6

• the larger bases
• adenine, guanine
• double ring structures

Question 7

difference between DNA and RNA

Answer 7

• DNA contains deoxyribose sugar
• RNA contains ribose sugar
• deoxyribose has 1 less oxygen atom than ribose

Question 8

what structure is DNA found in

Answer 8

double helix

Question 9

why are the 2 strands of DNA said to be antiparallel

Answer 9

• 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.

Question 10

complementary base pairing

Answer 10

• adenine pairs with thymine with 2 hydrogen bonds
• cytosine pairs with guanine with 3 hydrogen bonds

Question 11

how is a constant distance maintained between DNA strands

Answer 11

• 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

Question 12

why is RNA shorter than DNA

Answer 12

• 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

Question 13

RNA nucleotide

Answer 13

• pentose sugar ribose
• thymine base is replaced with uracil
• uracil is a pyrimidine that forms 2 hydrogen bonds with adenine

Question 14

how do RNA nucleotides form polymers

Answer 14

• formation of phosphodiester bonds in condensation reactions (Same as DNA)

Question 15

why can RNA leave the nucleus

Answer 15

• RNA polymers are small enough to leave via nuclear pores and travel to the ribosomes through cytoplasm

Question 16

what happens to RNA molecules after protein synthesis

Answer 16

• RNA molecules are degraded in the cytoplasm
• phosphodiester bonds are hydrolysed
• RNA molecules are released and reused

Question 17

how to extract DNA from plant material

Answer 17

• grind sample in mortar and pestle which breaks down cell walls
• mix sample with detergent which breaks down cell membrane, releasing cell contents into solution
• add salt which breaks hydrogen bonds between DNA and water molecules
• add protease enzyme which breaks down proteins associated with the DNA in the nuclei
• add layer of alcohol (ethanol) on top of the sample as 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
• DNA can be picked up by spooling it onto a glass rod