m2 nucleotides and nucleic acids

describe nucleotide structure

• nitrogenous base

• pentose sugar

• phosphate group

• rna has ribose sugar

what are the purine bases

• adenine

• guanine

what are pyrimidine bases

• thymine

• cytosine

• uracil

describe how nucleotides are joined

• nucleotides are joined together by a condensation reaction where water is removed

• phosphodiester bond is between carbon 3 and carbon 5 , known as 3 to 5 phoephodiester bond

describe structure of ATP

• ribose sugar

• adenine

• 3 phosphate groups

describe energy needed to break the phosphate groups in ATP

• only small amount of energy needed to break the last phosphate group off ATP

• large amount of energy is released when bonds are formed by the ‘free’ phosphate group which is involved in other reactions

describe reaction that breaks down ATP

• hydrolysis reaction and involves energy required reactions

• these are said to be coupled as they occur simultaneously

describe how it would be if it was opposite (ADP→ATP)

• to go from ADP to ATP it would be a condensation reaction

• energy supplied by respiration

describe structure of DNA

• contained 2 polynucleotide strand running in opposite direction , anti parallel strands which are held tg by hydrogen bonds

• 3 hydrogen bonds between cytosine and guanine

• 2 hydrogen bonds between adenine and thymine

• a purine always binds to a pyrimidine

• two strands of DNA twist around to form a double helix

• complimentary base pairs in the middle

describe semi conservative dna replication

• dna replicates during interphase

• dna helicase breaks hydrogen bonds between bases , double helix unwinds and each strand acts as a template

• free nucleotides from cytoplasm and assembly on the template DNA in complementary base pairs

• hydrogen bonds reform between bases

• dna polymerase joins nucleotides forming new sugar phosphate backbone

• two identical dna molecules have been produced

define semi conservative replication

each new dna molecule contains one of the old strands and one new strand

describe mehelson and stahl experiment

define gene

gene is a section of dna that codes for the sequence of amino acids in a polypeptide

define alleles

different versions of a gene

describe the nature of the genetic code

• dna controls protein structure by determining the amino acid sequence

• the code is a triplet code

• each sequence of 3 bases (codon) determines one amino acid so its non overlapping

• degenerate so some amino acids have more than one triplet code

• universal used across all organisms

• code is always read in one direction

describe extraction of dna practical

• crush sample to break down cellulose cell wall

• add detergent to dissolve plasma membrane

• add protease enzyme to break down histones associated with dna

• filter to remove any solids

• add salt to help dna clump together

• pour ethanol in , dna insoluble so should float to top

• precipitate formed

describe steps of transcription

• hydrogen bonds between complimentary base pairs broken , dna helicase helps w this

• free rna nucleotides form a complimentary strand (mRna)

• RNA polymerase helps form phosphodiester bonds in between the RNA nucleotides , helps form sugar phosphate backbone

• mRNA peels away from DNA and leaves nucleus through nuclear pore and DNA helix reforms

describe steps of translation

• mRNA attaches to a ribosome that is made of two subunits of rRNA

• anticodon on tRNA will find complimentary codon on mRNA bringing specific amino acid with it

• many Trnas come

• amino acids join together by peptide bonds to give a protein with specific primary stricture then go to secondary and tertiary