OCR Biology - Nucleic Acid

nucleic acid

2 large polymers made up of nucleotide monomers that store and transmit genetic information.

2 types of nucleic acid

DNA

RNA

nucleotide is made up of

a pentose sugar containing 5 carbon atoms

a phosphate group, an inorganic group that is acidic and negatively charged -PO₄^2-

a nitrogenous base - complex structure containing 1 or 2 carbon rings in its structure

nucleotides are linked by

condensation reaction forming a polymer called polynucleotide

at what carbon is pentose sugar does the phosphate group bond at

fifth carbon

the phosphate group forms what type of bond at the hydroxyl group of the 3rd carbon of the pentose sugar

a phosphodiester bond

phosphodiester bonds can be broken by

hydrolysis reactions

DNA full name

deoxyribonucleic acid

name of the sugar in DNA

deoxyribose - has one less oxygen compared to ribose

pyrimidines

smaller bases which contain single carbon ring structure cytosine, thymine, and uracil.

purines

the larger bases which contain a double carbon ring structure, specifically adenine and guanine.

DNA double helix

2 strands of polynucleotides coiled into a helix

the complimentary bases are held by which bond

hydrogen bonding

antiparallel

the 2 parallel strands are arranged so that they run in opposite directions to each other, with one strand running 5' to 3' and the other 3' to 5'.

GCAT

guanine cytosine adenine thymine

how many hydrogen bonds are formed between adenine and thymine

2

how many hydrogen bonds are formed between guanine and cytosine

3

pyrimidines always binds to

purines. the arrangement maintains a constant distance between dna backbone resulting in parallel polynucleotide chains

role of RNA

transfers genetic info from DNA to proteins that make up enzymes and tissues of the body

RNA contains which pentose sugar

ribose sugar

messenger RNA (mRNA)

relatively short section of the long DNA molecule corresponding to a single gene

in RNA thymine is replaced by

uracil

uracil is a pyrimidines and therefore

can form 2 hydrogen bonds with adenine

RNA nucleotides are held togather by

phosphodiester bonds through the condensation reaction

RNA in protein synthesis

RNA are so small that its small enough to leave the nucleus and travel to the ribosomes

after protein synthesis the RNA

RNA is degraded in the cytoplasm

phosphodiester bonds are hydrolysed

RNA nucleus are hydrolysed and reusued

steps in transcription

1. DNA helicase unwinds and unzips DNA breaking hydrogen bonds

2. Free RNA nucleotides pairs up with exposed bases by complimentary base pairing

3. RNA polymerase joins up RNA nucleotides by forming phosphodiester bonds. mRNA is made

4. mRNA leaves the nucleus through the nuclear pore and travels to ribosomes in RER for translation

steps in translation

1. mRNA binds to the ribosomes

2. tRNA is complimentary to the mRNA codon as mRNA contains specific amino acids and anticodons complimentary to the codon on the mRNA

3. Another tRNA with specific amino acids binds to the next complimentary codon on the mRNA

4. the first amino acid binds to the second amino acid through a peptide bond through peptidyl transferase

5. the ribosome moves along the mRNA, the tRNA leaves

6. steps 3 to 5 repeated again

similarities between DNA replication and transcription

DNA helicase unwinds and unzips the DNA molecule

the use of template strands

involves the use of free nucleotides

polymerase enzymes are involved in both

both involves hydrogen bonds between bases

both involves phosphodiester bonds

both involves complimentary base pairing

differences between DNA replication and transcription

DNA nucleotides are involved in replication and RNA nucleotides are involved in transcription

DNA replication involves the whole DNA molecule unwinding whereas transcription involves only a short section of DNA unwinding and unzipping aka in the gene

DNA polymerase is used in replication and RNA polymerase is used in transcription

uracil is used instead of thymine in transcription

in transcription hydrogen bonds are temporary

2 double stranded DNA molecule - product of replication and single stranded in replication is mRNA

only DNA features

pentose sugar is deoxyribose

double stranded

contains thymine

highly chemical

only mRNA feautures

contains uracil

can move through nuclear pores

quantity varies from cell to cell

single stranded

found in the cytoplasm

pentose sugar is ribose

features in both DNA and mRNA

contains GCA

contains covalent bonds

are both polynucleotides

found in the nucleus

has a sugar phosphate backbone

describe how two nucleotide chains are bonded togather

hydrogen bond between the complimentary nitrogenous bases

sugar phosphate backbone is connected by covalent bonds

antiparallel strands are held togather by

hydrogen bonds

DNA extraction

grind sample in mortar and pestel - breaks down cell walls

mix sample with detergent - breaks down the cell membrane releasing cell content into the solution

add salt - breaks hydrogen bonds between DNA and water molecules

add protease enzyme - break down proteins associated with DNA in the nuclei

add ethanol - alcohol causes DNA to precipitate out of the solution

why do we need energy

1. synthesis - the building of large molecules from smaller ones

2. transport - pumping molecules or ions across membranes by active transport

3. movement - protein muscle fibres in muscle cells requires energy to contract

ATP is

the universal energy currency

ATP is made from

nitrogenous base - adenine

pentose sugar - ribose

3 phosphate groups

how is atp released

energy is needed to break bonds and is released when bonds are formed

a small amount of energy is needed to break the weak bond holding the last phospate group in ATP

however a large amount of energy is released when this phosphate is then involved in other bond forming reactions