molecules of life

• define Organic Chemistry

  The study of chemistry focusing on the reactions, formation and role of carbon/hydrogen-based molecules
• what are the types of biological molecules

  • Carbohydrates
  • Proteins
  • Nucleic Acids
  • Lipids
• define Carbohydrates

  • Carbon-based molecules which are rich in hydroxyl groups (OH groups)
  • empirical formula of (CH2O)N
• Categories of carbohydrates based on size

  • Monosaccharides - single unit
  • Disaccharides - double unit
  • Polysaccharides - multiple units (can be hundreds/ thousands long)
• Monosaccharides

  • Single carbohydrate unit
  • commonly cyclic in nature
  • used as an energy source -> glucose/ fructose
• Disaccharides

  • Double carbohydrate units
  • produced by two monosaccharides joining together via a glycosidic bond
  • examples: sucrose / maltose / lactose
• Polysaccharides

  • Multiple carbohydrate units, hundreds/thousands of units long
  • energy storage -> glycogen/ amylose
  • structural component -> cellulose/ chitin
  • glycogen - formed by long continuous chains of a-1-4 glycosidic bonded glucose molecules with sporadic 1-6 glycosidic bond branches
  • cellulose - made up of long continuous chains of b-1-4 glycosidic bonded glucose molecules
• Formation of Glycosidic bond

  • Condensation reaction
  • Release of a molecule of water
  • example - 1-4 glucosidic bonding of two glucose molecules into a single maltose molecule
• define the roles of Proteins

  • reactions as catalysts
  • transportation and storage of molecules
  • mechanical support
  • immune protection and response
  • movement generation
  • transmission of nerve impulses
  • regulation of growth
  • organism differentiation
• define Amino acids

  Monomers that make up proteins, consisting of the same fundamental structure
• Categories of amino acids based on physical characteristics of their functional (R)-groups

  • Hydrophobic
  • Hydrophilic (Polar)
  • Positively charged
  • Negatively charged
• Peptide bonding

  • Binding of amino acids together by peptide bonding
  • condensation reaction between the Amide group (NH3+) and the carboxyl group (COO-)
• Levels of protein structure

  • Primary
  • Secondary
  • Tertiary
  • Quaternary
• define the Primary structure of proteins

  The order of amino acids within the polypeptide chain, unique to each protein and specified by genes
• Secondary structure

  • Repeating patterns of 3-Dimensional folding
  • due to hydrogen-bonding between non-neighbouring amino acids of the same peptide strand,
  • Alpha Helix, Beta Sheet, and Beta turn
• Tertiary structure

  • Folding of the overall protein structure due to the polarity of the amino-acids within the primary and secondary structures
  • with hydrophilic AAs on the exterior and hydrophobic AAs on the interior
• Quaternary structure

  • The non-covalent binding of different peptide chains to produce multiple subunit protein complexes
  • example - haemoglobin
• Nucleic Acids

  • DNA - double-stranded helical structure
  • RNA - single-stranded, transfer of genetic information into protein synthesis (mRNA / rRNA / tRNA)
• Types of RNA

  • mRNA (Messenger RNA): Transcripted DNA sequence which leaves nucleus containing information for protein synthesis
  • rRNA (Ribosomal RNA): site of protein synthesis
  • tRNA (Transfer RNA): carries amino acids to the site of protein synthesis
• Nucleic Acids: Structure

  • Nitrogenous base
  • Pentose Sugar
  • Phosphate group
• Nitrogenous bases


  • information storage allowing protein biosynthesis
  • Split into two sub-groups:

  1. Pyrimidines – Single Carbon/Nitrogen rings
  2. Purines – Double Carbon/Nitrogen rings

  • DNA - Cytosine, Guanine, Adenine, Thymine
  • RNA - Cytosine, Guanine, Adenine, Uracil
• Pentose Sugars

  • Forms 1/2 of the Sugar-Phosphate backbone of nucleic Acids
  • DNA - deoxyribose (1 OH group)
  • RNA - ribose (2 OH groups)
• Phosphate group

  • Forms the other 1/2 of the Sugar-Phosphate backbone of nucleic Acids
  • In DNA/RNA, these exist as Monophosphate, but Di/Triphosphate groups exist (E.G ATP)
• DNA

  • Two strands of nucleic acids run anti-parallel to each other
  • Bound together by hydrogen bonds
  • Adenine <-> Thymine, Guanine <-> Cytosine
  • tightly packed helical structure
  • the specific order of the nitrogenous bases is the genetic information in the DNA strand
  • different order of bases = different protein
• Lipids

  • large class of macromolecules which are at their core, hydrocarbons
  • Large numbers of carbon-carbon/carbon-hydrogen interactions
  • Highly Hydrophobic
  • Vast range of different functional groups which can alter the physical properties
  • Many different and varied functions within biological systems:

  1. Energy storage
  2. Cellular and sub-cellular barriers
  3. signaling
  4. insulation
• Lipid structure

  • Linear molecules
  • Cyclic molecules
• Triglycerides

  • Long-Chained Fatty Acid: Many C-C and C-H interactions (Non-Polar)
  • Glycerol Sugar: Multiple Oxygen-containing groups (Polar)
• Fatty Acids

  • Long-chained carboxylic acid molecules (4-48 carbons long)
  • Exist in states of saturation:
  • Unsaturated – No C=C
  • Monounsaturated – One C=C
  • Polyunsaturated – 2+ C=C
• Phospholipids

  • Glycerides made of two fatty acids chains and a phosphate group bound to a glycerol molecule
  • This produces an Amphipathic molecule with a hydrophobic AND hydrophilic section
  • This dual nature allows them to form a Phospholipid Bi-Layer
• Micelles formation

  1. Phospholipids will spontaneously group together forming Micelles

  2. The polar phosphate heads facing outwards and hydrogen bond to the surrounding water molecules

  3. The non-polar tails face inwards and interact with each other, producing a hydrophobic central core
• Phospholipid Bi-Layer

  • Used to produce a semi-permeable barrier which is used to separate cells from the external environment and segregates organelles from cytoplasm
  • Allows organisms to produce specific and regulated cell environments
• Steroids (lipids with fused ring structures)

  • Highly hydrophobic and are insoluble in water
  • Multiple uses: Precursors to many different steroid hormones, Precursor to Vitamin D, Precursor to bile salts, Aids in the stability and fluidity of animal cell membranes
  • example: cholesterol