Nucleic Acids

• what does a nucleotide consist of? phosphate group, pentose sugar and nitrogenous base
• DNA structure deoxyribonucleic acid, 1 phosphate, deoxyribose sugar, nitrogenous base of adenine, thymine, guanine or cytosine
• RNA structure ribonucleic acid, 1 phosphate, ribose sugar, nitrogenous base of adenine, uracil, guanine or cytosine
• ATP structure adenosine triphosphate, 3 phosphate groups, ribose sugar, base is adenine
• what type of reaction is the formation of ATP? endergonic reaction and condensation reaction
• Word equation for formation of ATP ADP + Pi → ATP
• Where does the energy to form ATP come from? comes from energy releasing reactions in cellular respiration
• What enzyme catalyses the formation of ATP? ATP synthetase
• What is ATP hydrolysed to? ADP + Pi
• How many kJ are released when ATP is converted to ADP and Pi? 30.6kJmol-1
• why is ATP the 'universal energy currency'? - provides energy to all reactions in all cells in all species - energy is released in small useable quantities - ATP is relatively small and soluble so it can be easily transported in cells to where it is required - use ATP for active transport, protein synthesis, cell division and muscle contraction
• What is a purine base? have a double ring, they are guanine and adenine
• What is a pyrimidine? have a single ring, these are thymine, cytosine and uracil
• What did Edwin Chargaffs results in the proportions of the bases in DNA demonstrate? - the percentage of purines was always equal to that of pyrimidines - percentage of adenine was equal to that of thymine - percentage of guanine was equal to that of cytosine
• what are the base pairs termed? (AT CG) complementary base pairs
• why are the molecules in RNA single stranded? the proportions of adenine and uracil / guanine and cytosine are not equal however complementary base pairing takes place in some areas of tRNA
• what are the two functions of DNA in cells? - as the base sequence codes for amino acid sequences in protein synthesis - replicating prior to cell division so that each daughter cell gets equal DNA
• structure of DNA - composed of two complementary polynucleotide strands - sugar-phosphate molecules are joined by condensation reactions making a phosphodiester bond - sugar-phosphate molecules form the two sugar-phosphate 'backbones
• what does the DNA two strands being 'antiparallel' mean? the strands run in opposite directions from 3' to 5' or 5' to 3
• what does 3' to 5' refer to? - the numbers of the carbons in the pentose - The base is joined to C1 and the phosphate to C5 - bonds to form the 'sugar-phosphate backbone' form between phosphate and C3 in the 5' to 3' direction
• what shape is DNA? double helix
• three types of RNA - ribosomal RNA (rRNA) - messenger RNA (mRNA) - transfer RNA (tRNA)
• what is rRNA? ribosomal RNA, made in nucleolus, is a single component of ribosomes
• what is mRNA? messenger RNA, single stranded, made in the nucleus, mRNA carries the code from DNA in the nucleus
• what is tRNA? transfer RNA, single stranded polynucleotide of RNA twisted into a clover-leaf shape. - tRNNA carries amino acids to the ribosomes
• what were Meselson and Stahl's 3 possible mechanisms? - conservative replication - dispersive replication - semi-conservative replication
• what is conservative replication? DNA molecule would be copied from the original
• what is dispersive replication? sections of the DNA molecule would be copied and spliced together, making each new DNA molecule a mix of original and new DNA
• what is semi-conservative replication? the two poly-nucleotide chains would part and new nucleotides attatch to each of the chains so each ew molecule has an original and a new one
• Meselson and Stahl's experiment E.coli was easily grown in a flask of culture medium and replicate their cells every 20 minutes - E.coli was in a culture medium with only 15N isotopes until all bases contained 15N - when centrifuged, at the bottom - A sample of E.coli was then transferred to a new culture medium containing 14N and allowed to replicate once, when centrifuged was at an intermediate position - first,generation = not conservative because had half eavy and half light nucleotides - generation 2 = not dispersive because if dispersive would have more 14N than N and the DNA band would ...
• DNA replcation - DNA helicase unzips the hydrogen bonds holding the two polynucleotide chains together working in the 'replication fork' area - DNA polymerase joins new nucleotides to their complementary bases by catalysing formation of phosphodiester bonds
• describe transcription - Gene is a section of DNA that codes for a polynucleotide, contain introns and exons - Gene is unwound and unzipped by DNA helicase; means that the hydrogen bonds between the two polynucleotide chains are broken - original strand acts as a template for the new strand - RNA nucleotides align opposite to their complementary base pairs - RNA polymerase joined the nucleotides together forming ribose-phosphate backbone, a pre mRNA is formed
• what are exons? coding parts
• what are introns? non-coding parts
• what is every 3 bases on mRNA called? a codon
• how many codons can a ribosome accommodate? 2 codons
• translation - tRNA in cytoplasm is activated, correct amino acid binds to the amino acid binding site - when two tRNA molecules occupy both ribosome sites, the amino acids are brought close to form a peptide bond - ribosome moves along the mRNA by one codon, first tRNA is released from the amino acid and ribosome and returns to the cytoplasm to be reactivated - process repeats until 'stop' codon is reached
• what does the golgi body do? - modifying and packaging proteins - folds polypeptide to make protein - polypeptide can be folded to make a protein, it may have no protein groups joined to it (prosthetic groups)
• what does the code being degenerate mean? some amino acids have more than one code
• what does the genetic code is universal mean? the same in all living things, so each specific codon codes for the same amino acid in all species