lecture twelve - nucleotides, nucleosides, DNA, RNA

Question 1

major functions of nucleotides and nucleic acids

Answer 1

carry out a number of cellular functions
store genetic information
transcribe and translate genetic information (mRNA, tRNA, rRNA)
carry out enzymatic reactions
energy storage and transfer
signaling molecules
redox co-enzymes

Question 2

3 components found in nucleotides and nucleic acids

Answer 2

nitrogenous bases, sugar residues, phosphorus
phosphate residue can act as acids

Question 3

purine

Answer 3

6-m ring, 5-m ring
adenine (DNA, RNA)
guanine (DNA, RNA)

Question 4

pyrimidine

Answer 4

6-m ring
cytosine (DNA, RNA)
thymine (DNA)
uracil (RNA)

Question 5

how does guanine differ form adenine?

Answer 5

guanine has an amino group at C2 and a carbonyl group at C6; adenine has an amine group at C6

Question 6

nucleoside

Answer 6

heterocyclic base combined with a sugar (sugar + base, no phosphate)

Question 7

N-glycosidic bond

Answer 7

covalent bond, beta-orientation of the bond from the anomeric carbon of the sugar
no free rotation due to double bond form anomeric carbon to a nitrogen atom of the base

Question 8

phosphoester bond

Answer 8

link sugar and phosphate to form a nucleotide

Question 9

structure of ATP

Answer 9

3 phosphate groups attached to the sugar
hydroxyl group of the ribose becomes attached at the 5 position, phosphoester linkage

Question 10

two anhydride bonds of ATP

Answer 10

used as reservoirs of chemical energy in biological reactions; hydrolysis of these bonds are used in chemical reactions

Question 11

how is ATP hydrolysis coupled to unfavorable reactions to promote formation of reaction products?

Answer 11

the energy released by ATP hydrolysis can be coupled to energetically unfavorable biological reactions to promote product formation
both phosphoanhydride bonds of ATP release a high amount of energy upon hydrolysis – this energy is utilized to promote unfavorable reactions, glycolysis and TCA cycle

Question 12

how is energy released from the anhydride bonds?

Answer 12

energy released from anhydride bonds with the breakdown of organic compounds and is coupled to the synthesis of ATP

Question 13

how can the absorbance of UV light in the range of 260 nm be used to determine the concentration of nucleotides and nucleic acids?

Answer 13

each base has a different spectra between 240-300 nm region

Question 14

phosphodiester bond and its synthesis

Answer 14

occurs between nucleotides, monomers that build nucleic acid, to form the sugar-phosphate backbone
phosphodiester bond formation occurs by the removal of a water molecule when 2 hydroxyl groups from 2 different sugars bond with a phosphate group

Question 15

how are phosphodiester bonds used to link nucleotide units together in DNA and RNA?

Answer 15

sugar residues are connected by 3-5’ phosphodiester bonds

Question 16

3’ end

Answer 16

terminal hydroxyl end on the 3 position of the lower sugar

Question 17

5’ end

Answer 17

hydroxyl group attached to the carbon at the 5 position of the upper sugar

Question 18

orientation of RNA and DNA

Answer 18

5’ end to the left, 3’ end to the right
upper structure = free OH groups at the 5’ and 3’ ends
lower structure = OH groups are phosphorylated

Question 19

DNA

Answer 19

double helix, antiparallel
AT | CG nucleotide units contain deoxyribose
sugar residues are connected by 3-5 phosphodiester bonds

Question 20

RNA

Answer 20

single helix, AU | CG nucleotides contain ribose
sugar residues connected by 3-5 phosphodiester bonds

Question 21

DNA double helix characteristics

Answer 21

NEGATIVE P residues are on the OUTSIDE of the helix
backbone is covalently bound with the base pair planar and perpendicular to the inside of the helix
2H bonds between AT
3H bonds between CG
stabilized by aromatic stacking of successive bases
exterior = negative and polar (phosphate)
interior = hydrophobic for H bonding

Question 22

base pairing involves one of each

Answer 22

purine and pyrimidine

Question 23

which base pairing is stronger?

Answer 23

GC is a bit stronger because it is triple bonded; AT is only doubly bonded