Ch. 4 Nucleic Acids

what is a nucleic acid

a polymer of nucleotide momomers

nucleotide made up of

1. a phosphate group

2. a five carbon sugar

3. a nitrogenous base

5 carbon sugar in DNA

deoxyribose (H at 2’)

5 carbon sugar in RNA

ribose (OH at 2’)

sugar is defined by

the 2’ carbon

phosphate bonds to

sugar molecule

sugar molecule bonds to

nitrogenous base

purine

Adenine, Guanine (double bases)

pyrimidine

Cytosine, Uracil, Thymine (single based)

how nucleotides make nucleic acid

monomers link to polymerize and form polymers

polymerization requires

energy

nonspontaneous

does not happen on its own, requires energy input to continue

is polymerization spontaneous or nonspontaneous

nonspontaneous

how do momomers polymerize

condensation(dehydration) reactions

condensation rxn

remove water molecule to build bond

hydrolysis rxn

reverse reactions that break polymers apart by adding a water molecule (add H2O to break bond)

is a condensation rxn anabolic or catabolic

anabolic

is a hydrolysis rxn anabolic or catabolic

catabolic

a phosphodiester bond is made between

3’ OH of the existing and 5’ phosphate of the incoming (always true)

the backbone of DNA/RNA is made of

sugar phosphate backbone

what is this backbones characteristic

hydrophilic

nitrogenous bases relationship with water

hydrophobic (scared of water)

major groove

exposed bases that face you

minor groove

hidden bases away from us

deoxyribonucleotide

the sugar is deoxyribose (lacking oxygen)

ribonucleotides

sugar is ribose

in both sugars in RNA and DNA what is the same

an OH is bonded to 3’ carbon

sugar phosphate backbone directionality

one end has unlinked 5’ carbon, the other end has unlinked 3’ carbon

nucleotide sequence written

5’—>3’

phosphate is where

5’

OH is where

3’

endergonic

absorbs energy from surroundings

polymerization is exer or endergonic

endergonic (requires energy, catalyzed by enzymes)

DNA and RNA primary structure

nucelotide sequence

chargaff empirical rules for DNA

1. total number of purines and pyrimidines is the same

2. number of A’s and T’s are equal and C’s and G’s are equal

xray crystallography

X-ray crystallography provided evidence that DNA had a regular and repeating structure and was helical

watson and crick discovered

DNA is antiparallel, form double helix, sugar-phos backbone is facing our, nitro bases face in

A—T have how many H bonds

two (so does A—U)

C—G has how many H bonds

three

what bond holds strands together

hydrogen bond

what bond holds complementary base pairs together

hydrogen bonds

Function of DNA (general)

• store and transmit biological info

• carries info required for growth and reproduction

• the language of nucleic acids directs protein synthesis

DNA’s stability

• makes it a reliable store for genetic info

• less reactive than RNA

• more resistant to chemical degradation (bc double helix)

RNA primary structure

uracil instead of thymine,

contains ribose instead of deoxy

why is RNA more reactive

• the presence of OH (less stable)

RNA secondary sturcture

hairpin (single stranded RNA folds and loops)

DNA secondary structure

antiparallel, double helix

RNA tertiary structure

when secondary hairpin folds into more complex shapes (like tRNAs)

RNA functions as

• info contaning

• catalyst

• can self replicate

RNA is versatile because

it can function as a catalytic molecule

ribozymes

made up of RNA and protein: enzyme-like RNAs that make up ribosomes…