Nucleotide and DNA structure

• Nucleic acids contain oxygen, hydrogen, carbon, nitrogen and phosphorus
• RNA:

  • a polynucleotide that has the pentose sugar ribose rather than deoxyribose
  • contains the bases adenine, uracil, guanine or cytosine
  • can be turned into mRNA, tRNA, rRNA
• a nucleotide is made up of a phosphate, a ribose sugar and a base

  
• nucleotides bind together through condensation reactions to form a polynucleotide
• a phosphodiester bond is formed between the 3' hydroxyl group of one nucleotide and the 5' phosphate group of the next through a condensation reaction
• There are four different bases:

  • thymine, T
  • adenine, A
  • guanine, G
  • cytosine, C
• Complementary base pairings:

  • A-T
  • G-C
• hydrogen bonds provide lots of strength between bases
• guanine and cytosine have more hydrogen bonds so the more of them there are the more stable the DNA molecule
• Differences between RNA and DNA:

  • doesn't contain thymine but instead contains uracil
  • sugar is ribose not deoxyribose
  • the nucleotide strand is a single strand, not double
• ATP contains a ribose sugar, an adenine base and 3 phosphate groups

  
• ATP:

  • energy is stored in the bonds between the phosphates, when they are hydrolysed energy is released
  • phosphates that have been seperated from ATP can be used to phosphorylate other molecules in cells to make them more reactive
• phosphorylate means to add on a phosphate group (done in ADP to turn it into ATP)
• mRNA:

  • a complimentary copy of a portion of DNA
  • carries some DNA code (codon) to the ribosomes
  • linear in shape
• tRNA:

  • decodes mRNA into a polypeptide brings amino acids to the ribosomes, clover shaped and carries anticodons
• An anticodon identifies which tRNA binds to which mRNA
• rRNA:

  • forms the ribosomes
  • structure for translation
  • no codons or anticodons present
• DNA is stable because:

  • the phosphodiester backbone protects the more chemically reactive organic bases inside the helix
  • interactive forces between base-base stacking
• ATP contains a ribose group, an adenine base but has 3 phosphate groups, energy is stored between the phosphate bonds and when hydrolysed the energy is released
• RNA contains the base uracil instead of thymine
• RNA contains the sugar ribose instead of deoxyribose
• RNA is single stranded