ch3 - nucleic acids

what are nucleotides and what are nucleic acids

nucleotides are monomers that join to form polymer nucleic acids

what is the general structure of nucleotides

consist of 3 components:

-pentose monosaccharide (5 carbon sugar)

-phosphate group

-nitrogenous base

what is a polynucleotide

consist of many nucleotides joined together by multiple phosphodiester bonds - forming a chain

how is a polynucleotide formed

phosphate group on carbon 5 (5’ - 5 prime) of one nucleotide reacts with hydroxyl (OH) on carbon 3 (3’ - 3 prime) of an adjacent nucleotide forming phosphodiester bonds which joins them together

> undergoes a condensation reaction which forms H2O as a by-product

how can phosphodiester bonds be broken

hydrolysis reaction

by adding water it breaks phosphodiester bonds which releases individual nucleotides

what is a phosphodiester bond

it is a type of covalent bond which joins nucleotides together

what is the difference between polynucleotides and nucleic acids

polynucleotides refers to the chain of nucleotides which a nucleic acid is made of

-nucleic acid consist of one or more polynucleotide chains

what are the 2 types of nucleic acids and state their full names

DNA - deoxyribonucleic acid

RNA - ribonucleic acid

what is the difference between the structures of these nucleic acids

difference - DNA has one less oxygen atom compared to RNA

deoxy = -1 less oxygen

name the 4 types of nitrogenous bases

adenine

guanine

thymine

cytosine

what are pyrimidines

the smaller nitrogenous bases - consist of 1 carbon ring structure

(pYrimidines) > cytosine, thymine (in RNA is replaced by uracil)

what are purines

the larger nitrogenous bases - consist of 2 carbon ring structure

> adenine, guanine

what is meant by complementary base paring

refers to the specific pairing of bases

- a nitrogenous base will always pair with its other complementary base

what are the complementary bases and what bonds do they form

Adenine + Thymine (always form 2 hydrogen bonds)

Guanine + Cytosine (always form 3 hydrogen bonds)

what is a difference between the bases that are found in DNA vs RNA

in RNA thymine is replaced by uracil

> uracil is less stable than thymine & requires less energy to be produced which is more efficient for RNA since RNA is temporary

what is the structure of DNA

-DNA is made up of two antiparallel strands of polynucleotides which wrap around each other forming a double helix

-the two strands are held together by hydrogen bonds that form between the complementary bases

what does antiparallel mean

they run in opposite directions - one strand runs from 5’ to 3’ and the other strand runs from 3’ to 5’

what does 5’ end or 3’ end mean

it refers to which carbon is exposed on the last nucleotide in the strand

what is meant by the sugar phosphate backbone

refers to the alternating sequence of sugar (pentose monosaccharide) and phosphate groups joined together by phosphodiester bonds

-it runs from 5’ to 3’ direction

name 3 properties of DNA

stable structure - due to the sugar phosphate backbone which is held together by strong covalent bonds (phosphodiester bonds)

easy to separate - due to the weak hydrogen bonds holding the nitrogenous bases together

what is meant by a codon

a group of three bases - triplet of bases

name the 3 types of RNA

ribosomal - rRNA

transfer - tRNA

messenger - RNA

what is the function of rRNA

it reads the order of amino acids and links them together accordingly

what is the function of mRNA

to carry a copy of DNA sequence to a ribosome in the cytoplasm

outline 2 features of mRNA

it is single stranded

it is made up of codons, every 3 set of bases code for one specific amino acid

what is the function of tRNA

it brings specific amino acids to the ribosome during translation to build a polypeptide chain

outline 3 features of tRNA

single stranded and folded to form a clover leaf shape

has an amino acid binding site on the end

has a anticodon, triplet of bases, on other end complementary to the bases on mRNA codon - enabling tRNA to bring the required amino acid to build the polypeptide chain

what is DNA replication referred to as

semi conservative

why is DNA replication semi conservative

because during replication 2 polymer chains of DNA are created

> each chain consist of old template strand & a new template strand

name the 2 enzymes involved in DNA replication

DNA helicase

DNA polymerase

what occurs during DNA replication

1. DNA helicase breaks the hydrogen bonds between the complementary bases causing double helix to unwind & the 2 strands to separate

-the strands will now act as templates

2. free DNA nucleotides found in nucleus will pair up with the exposed bases along the template strand by complementary base pairing and hydrogen bonds will form between the base pairs

3. DNA polymerase will join the adjacent nucleotides together forming phosphodiester bonds and the sugar phosphate backbone

what are the 4 features of the nature of the genetic code

triplet

non-overlapping

degenerate

universal

what do these features mean

triplet - genetic code is read in groups of three bases, codons

non-overlapping - each codon is read separately as a discrete unit

degenerate - different combinations of codons can code for the same amino acid

universal - same triplet of bases will code for the same amino acid in all organisms