Molecules of Life

• Pyrimidines


  can be a single six-ring structure

  Cytosine, Uracil and Thymine
• Purines


  Can be a double ring structure

  Adenine and Guanine
• In nucleotides, the pentose ring is attached to the nitrogenous base via a N-glycosidic bond.
• Base + Sugar = Nucleoside
• Nucleoside+ Phosphate = Nucleotide
• Erwin Chargaff (1905-2002)


  observed that any DNA double strand which follows the base pairing rules must have equal amounts of A and T, and equal amounts of G and C.
• Forming polymers involves condensation.
• A-T pair has 2 hydrogen bonds
• G-C pair has 3 hydrogen bonds
• Antiparallel: The 5'-end of one strand is opposite the 3'-end of the other.
• Paired: two strands anneal to each other and form a double helix
• Complementary: always A opposite T, C opposite G.
• The major groove is generated by the twist of the helix
• The minor groove is the base-containing gap between the DNA backbones.
• Choice of DNA-form is dependent on sequence, ionic conditions and temperature.
• A-T rich regions melt at a lower temperature than G-C rich regions
• An orbital is a three dimensional description of the most likely location of an electron around an atom.
• There are 4 types of orbitals: s,p,d and f
• The hybridization of carbon in diamond, graphite and acetylene is respectively: sp3, sp2 and sp.
• The DNA structure was discovered in 1963.
• DNA was discovered in 1953 by Francis Crick and James Watson.
• DNA was first discovered by a Swedish chemist named Johann Friedich Miescher.
• Humans have 3 x 10^9 base pairs in their DNA.
• DNA is highly negatively charged.
• dAMP means deoxy-adenosine monophosphate
• RNA is unstable because of the -OH group
• Ribosomes contain about 20% proteins, the bulk of ribosomes are rRNA.
• Watson and Crick discovered DNA has a double helix
• DNA is negatively charged because of the phosphate group
• The lipid bilayer can be destroyed by a detergent
• DNA can be separated according to its size
• There are 64 different possible combination of the 4 letters
• Start codon is AUG
• There are three stop codons: UAA, UAG, and UGA.
• The structure of protein determines its function.
• Monosaccharides are single sugar unit.
• Monosacchrides are colorless, crystalline and soluble. (insoluble in non-polar solvents)
• Monosaccharides can react with each other to form disaccharides connected by an O-glycosidic bond.
• A few common disacchrides found in nature are:

  maltose, lactose and sucrose
• Lipids store energy in the carbon