nucleic acids

what are nucleic acids?

large long polymer molecules contained in the nucleus of the cell important in the storage and transfer of genetic information used to make proteins

what are the two types of nucleic acids?

• DNA - deoxyribonucleic acid

• RNA - ribonucleic acid

what are nucleic acids made of?

• carbon

• hydrogen

• oxygen

• nitrogen

• phosphorus

what is the difference between DNA and RNA?

dna contains deoxyribose sugar whereas rna contains ribose sugar containing an extra oxygen on the second carbon

what is the phosphate group?

negatively charged inorganic chemical

what do the nitrogen bases do?

make up the five different nucleotides

how are nucleotides formed?

a phosphate group, sugar and base are joined together by a condensation reaction

how are polynucleotides formed?

nucleotides are joined together through condensation reaction creating a phosphodiester bond and a sugar phosphate backbone

purine bases :

• adenine

• guanine

• double ring structure

pyrimidine bases :

• thymine

• cytosine

• uracil

• single ring structure

how do bases bond together to create DNA molecule?

• two hydrogen bonds between a and t

• three hydrogen bonds between c and g

what bonds the sugar and phosphate group together?

covalent bond

structure of DNA :

• many nitrogenous bases bonded by hydrogen bonds

• double helix

• antiparallel

• sugar phosphate back bone

how to break polynucleotides down?

break the phosphodiester bonds by hydrolysis

PUAG

purine a g

t for 2

thymine has two hydrogen bonds

reasons for DNA replication :

• cell division (mitosis)

• reproduction (meiosis)

semi conservative DNA replication :

• hydrogen bonds between bases are broken by dna helicase

• double helix structure unwinds

• free activated nucleotides join unpaired bases

• hydrogen bonds form

• dna polymerase cause phosphodiester bonds to form between nucleotides

DNA helicase :

breaks hydrogen bonds between bases and unwinds the molecule

DNA polymerase :

form covalent bonds between phosphates and sugars catalysing formation of new polynucleotide chain

DNA ligase :

joins together short sections of the lagging and leading strand of polynucleotides

single strand binding protein :

keeps dna strands separated during replication

what is the genetic code?

sequence of bases along dna coding for amino acids to form a specific polypeptide

what does it mean the genetic code is universal?

the same sequence of bases codes for the asame amino acids in all organisms

the triplet code :

three bases code for one amino acid

non overlapping :

base code is read in groups of three

degnerate :

more than one triplet can code for each amino acid

what are the three types of dna replication?

• conservative

• semi conservative

• dispersive

which way does DNA polymerase read the polynucleotide chain?

5’ to 3’

when is mRNA created?

when a polypeptide is required the triplet code is converted into a molecule of mRNA

difference between DNA and mRNA?

• mRNA single stranded

• contains ribose instead of deoxyribose

• contains uracil

mRNA is non overlapping :

each base is only part of one codon coding for one amino acid

protein synthesis - transcription :

• dna helicase breaks hydrogen bonds

• rna polymerase matches complementary rna nucleotides

• c-g and a-u

• mRNA is formed

• dna behind rna rejoins double helix

• when rna polymerase reaches stop codon the chain is terminated

• pre mRNA detaches leaving through nuclear pore

mRNA :

• used to transfer the dna code to the cytoplasm

• complementary to dna code

• in cytoplasm associates with ribosomes

• determines sequence of amino acids

protein synthesis - translation :

• mRNA attaches to ribosome

• tRNA attaches with complementary anticodon

• tRNA is attached to amino acid

• ribosome moves along mRNA

• enzymes and ATP are used to form peptide bond between amino acids

• repeated until a stop codon

features of tRNA :

• amino acid attachment site

• hydrogen bonds

• anticodon

• nucleotides

• each amino acid has a different anticodon

• clover shaped

what is synthesis?

the building of large complex molecules from smaller ones e.g. protein synthesis

what is transport?

pumping molecules or ions across membranes by active transport

adenosine triphosphate :

• universal energy currency cells

• store of potential chemical energy

• hydrolysed to release chemical energy

structure of ATP :

• adenine - nitrogenous base

• ribose - pentose sugar

• three phosphate groups

how does ATP release energy?

• energy is released when bonds are formed (exothermic)

• small amount of energy required to break the last phosphate groups bond

• more energy released when new bonds are formed

• overall net energy is released

properties of ATP :

• small - easily transportable

• water soluble

• immediate energy source

• small quantities so energy is not wasted

• easily regenerated

what is a?

phosphate group

what is b?

nitrogen containing base

what is c?

pentose sugar