Biomolecules

• Biomolecules


  Chemical compounds found in living organisms, including organic and inorganic compounds
• Analysis of chemical composition in a tissue

  1. Grind living tissue in trichloroacetic acid to get filtrate (acid-soluble pool) and retentate (acid-insoluble fraction)

  2. Filtrate contains biomicromolecules (molecular weight less than 1000 Dalton)

  3. Retentate contains biomacromolecules (molecular weight greater than 1000 Dalton)
• Analysis of inorganic compounds


  Weigh tissue (wet weight), dry it, fully burn to oxidize carbon compounds, and analyse the ash for inorganic elements and compounds
• Comparison of elements in non-living and living matter
• Biomicromolecules


  Molecules with molecular weight ranging from 18 to 800 Dalton, found in the acid-soluble pool representing the cytoplasmic composition
• Biomicromolecules


  • Amino acids
  • Lipids
  • Sugars
  • Nitrogen bases
• Amino acids


  • Compounds formed of an amino group (-NH2), an acid group (-COOH), H and a variable group (R)
  • They are substituted methanes with -NH2 and -COOH attached to the same carbon atom (α-carbon)
• Types of amino acids

  • Acidic
  • Basic
  • Neutral
  • Aromatic (e.g. tyrosine, phenylalanine, tryptophan)
• Classification of amino acids

  • Essential (cannot be synthesized by the body)
  • Non-essential (can be synthesized by the body)
• Zwitterionic form of amino acids

  When both -NH2 and -COOH are ionized
• Lipids


  • Water insoluble, contain C, H and O but with fewer oxygen atoms
• Types of lipids


  • Simple lipids
  • Compound lipids
  • Derived lipids
• Fatty acids


  Lipids with a hydrocarbon chain ending in a -COOH group
• Types of fatty acids

  • Saturated (no double/triple bonds)
  • Unsaturated (one or more C=C bonds)
• Glycerol


  A trihydroxy propane molecule
• Formation of mono-, di- and triglycerides

  Esterification of fatty acids with glycerol through ester bonds
• Fats and oils


  Triglycerides with higher and lower melting points respectively
• Compound lipids


  Esters of fatty acids and alcohol with additional groups, e.g. phospholipids
• Derived lipids


  Products of hydrolysis of simple and compound lipids, e.g. cholesterol
• Sugars (carbohydrates)


  Sweet, water-soluble compounds with C:H:O ratio of 1:2:1, e.g. glucose, ribose
• Nitrogen bases


  • Purines (adenine, guanine)
  • Pyrimidines (cytosine, thymine, uracil)
• Nucleosides


  Compounds formed by linking a nitrogen base with a sugar
• Nucleotides


  Compounds formed by linking a nucleoside (nitrogen base + sugar) with a phosphate
• Nucleotides are heterocyclic compounds that make up nucleic acids (DNA and RNA)
• Biomacromolecules


  Biomolecules with molecular weight greater than 1000 Dalton, including proteins, polysaccharides, and nucleic acids
• Lipids are not strictly macromolecules but are part of the acid-insoluble fraction due to their arrangement into structures like cell membranes
• Average composition of cells
• BIOMACROMOLECULES


  • Proteins
  • Lipids
  • Nucleic acids
  • Polysaccharides
• Biomacromolecules


  Biomolecules having molecular weight greater than 1000 Da
• Lipid is not strictly a macromolecule as its molecular weight does not exceed 800 Da. But it comes under acid insoluble fraction because many lipids are arranged into structures like cell membranes.
• When a tissue is grinded, cell membranes are broken and form water insoluble vesicles. They cannot be filtered along acid soluble fraction.
• Average composition of cells

  • Water (70-90%)
  • Protein (10-15%)
  • Carbohydrates (3%)
  • Nucleic acids (5-7%)
  • Ions (1%)
• Proteins


  Heteropolymer of amino acids
• Peptide bond


  Formed when -COOH group of one amino acid reacts with -NH2 group of next amino acid by releasing a molecule of water (dehydration)
• Functions of protein


  • Growth and tissue repair
  • Transport nutrients across cell membranes
  • Acts as intercellular ground substance
  • Acts as antibodies to fight infectious organisms
  • Acts as receptors
  • Some are hormones, enzymes, pigments etc.
• Collagen


  Most abundant protein in the animal world
• RuBisCO


  Most abundant protein in the biosphere
• Structural levels of protein

  • Primary structure
  • Secondary structure
  • Tertiary structure
  • Quaternary structure
• Primary structure


  Describes the sequence of amino acids, i.e. positional information in a protein
• Secondary structure


  One or more polypeptide chains are folded in the form of a helix or beta-pleated sheet