Biomolecules

• There is a wide diversity in living organisms in our biosphere
• Elemental analysis

  Analyzing the elements and their respective content per unit mass of a living tissue
• All the elements present in a sample of earth's crust are also present in a sample of living tissue
• The relative abundance of carbon and hydrogen with respect to other elements is higher in any living organism than in earth's crust
• How to analyse chemical composition

  1. Grind living tissue in trichloroacetic acid

  2. Obtain filtrate (acid-soluble pool) and retentate (acid-insoluble fraction)

  3. Identify organic compounds in acid-soluble pool
• All the carbon compounds that we get from living tissues can be called 'biomolecules'
• Determining inorganic elements and compounds in living tissues

  1. Weigh wet tissue

  2. Dry tissue to get dry weight

  3. Burn tissue to get ash

  4. Ash contains inorganic elements and compounds
• Inorganic constituents of living tissues

  • Sodium
  • Potassium
  • Calcium
  • Magnesium
  • Water
  • Compounds like NaCl, CaCO3, PO4, SO4
• Amino acids

  Organic compounds containing an amino group and an acidic group on the same carbon (α-carbon)
• Amino acids

  • Glycine
  • Alanine
  • Serine
• Lipids

  Generally water insoluble, can be simple fatty acids or more complex like fats, oils, phospholipids, cholesterol
• Nucleic acids

  Consist of nucleotides, which have a nitrogen base, a sugar, and a phosphate group
• Nitrogen bases

  • Adenine
  • Guanine
  • Cytosine
  • Uracil
  • Thymine
• Nucleosides

  • Adenosine
  • Guanosine
  • Thymidine
  • Uridine
  • Cytidine
• Primary metabolites

  Biomolecules with identifiable functions and known roles in normal physiological processes
• Secondary metabolites

  Biomolecules found in plants, fungi and microbes, with unclear functions but often useful for human welfare
• Biomacromolecules

  Biomolecules with molecular weights greater than 10,000 daltons, including proteins, nucleic acids, polysaccharides and lipids
• Lipids are not strictly macromolecules despite being in the acid-insoluble fraction
• Average composition of cells

  • Water (70-90%)
  • Proteins (10-15%)
  • Carbohydrates (3%)
  • Lipids (2%)
  • Nucleic acids (5-7%)
  • Ions (1%)
• Proteins

  Polypeptides, linear chains of amino acids linked by peptide bonds
• Proteins are heteropolymers, as they contain 20 different types of amino acids
• Certain amino acids are essential and must be obtained through diet, while others are non-essential and can be synthesized by the body
• Composition of living tissue from abundance point of view

  • Water
  • Other components
• Water is the most abundant chemical in living organisms
• Proteins


  • They are heteropolymers, not homopolymers
  • They are a polymer of 20 types of amino acids
• Certain amino acids are essential for our health and have to be supplied through our diet
• Amino acids can be essential or non-essential
• Functions of proteins


  • Transport nutrients across cell membrane
  • Fight infectious organisms
  • Hormones
  • Enzymes
• Collagen is the most abundant protein in the animal world
• Ribulose bisphosphate Carboxylase-Oxygenase (RuBisCO) is the most abundant protein in the whole of the biosphere
• Polysaccharides


  Long chains of sugars, threads containing different monosaccharides as building blocks
• Polysaccharides


  • Cellulose
  • Starch
  • Glycogen
  • Inulin
• Cellulose


  • It is a homopolymer consisting of only one type of monosaccharide, glucose
  • It does not contain complex helices and hence cannot hold I2
• Starch

  • It forms helical secondary structures and can hold I2 molecules in the helical portion
• Plant cell walls are made of cellulose
• Paper made from plant pulp and cotton fibre is cellulosic
• Exoskeletons of arthropods


  They have a complex polysaccharide called chitin
• Nucleic acids

  Polynucleotides, the building block is a nucleotide
• Nucleotide

  • It has three chemically distinct components: a heterocyclic compound, a monosaccharide, and a phosphoric acid or phosphate
• Nitrogenous bases in nucleic acids

  Adenine, guanine, uracil, cytosine, and thymine