Biomolecules 1

• Types of Biomolecule


  • Carbohydrates
  • Lipids
  • Protein
  • Nucleic acids
• Biomolecules are compounds that occur naturally in living organisms
• Biomolecules consist primarily of carbon, hydrogen and oxygen plus nitrogen, phosphorus and sulphur
• Biomolecules are necessary for the existence of life
• Biomolecules can be simple molecules or form complex polymers
• Carbohydrates


  Compounds with the general formula CH2O
• Types of monosaccharides


  • Hexoses (C6H12O6) e.g. Glucose, Fructose, Galactose
  • Pentoses (C5H10O5) e.g. ribose, deoxyribose
• Disaccharides


  Soluble sugars formed from two monosaccharides joined together by a glycosidic linkage
• Polysaccharides


  Polymerized monosaccharides - large, complex, branched molecules that are insoluble in water
• Polysaccharides


  • Starch
  • Cellulose
  • Chitin
  • Glycogen
• Roles of Carbohydrates


  • Energy sources
  • Structural functions
• Glucose


  Broken down during glycolysis to pyruvic acid which feeds into the citric acid cycle and electron transport chain to produce ATP
• Cellulose


  Forms a major structural component of plant cell walls
• Chitin


  An important structural molecule in arthropods
• Uses of Carbohydrates in Forensic Science


  • Identification can differentiate between plant and animal material
  • Products of carbohydrate decomposition can be important biomarkers in estimations of post mortem interval
  • Identification can provide useful intelligence to investigators when carbohydrates are used to cut drugs
• Carbohydrates used to cut drugs


  • Dextrose
  • Fructose
  • Lactose
  • Sucrose
  • Manitol
  • Inisitol
• Lipids


  Esters of fatty acids and alcohols, synthesised in the Smooth ER
• Lipids consist of a polar (hydrophilic) head and one to three non-polar (hydrophobic) fatty acid tails, usually 14-24 carbon groups long
• Key functional roles of Lipids


  • Basic building blocks of biological membranes
  • Energy storage
  • Cell signalling
• Classes of lipid heads in biological membranes


  • Glycolipids
  • Sterols
  • Phospholipids
• Uses of Lipids in Forensic Science


  • Classification and identification of bacteria
  • Distinguishing eukaryotic microbes such as fungi and protozoa
  • Detecting microbes in water contamination
  • Identifying burial sites and estimating post-mortem interval
  • Identifying the source of fatty acids used in food supplements
• Lipid analysis studies


  • Identification of a disinterred grave by molecular and stable isotope analysis
  • Lipid analysis on potential grave soil products
  • Forensic identification of seal oils using lipid profiling and statistical analysis
• Proteins


  Abundant and highly diverse molecules, synthesised in the Rough ER, play key roles in almost all biological processes
• Types of Proteins


  • Structural proteins
  • Biochemical catalysts or regulatory proteins
• The expression of different sets of proteins results in different cell types with specialist functions
• Amino Acids


  Consist of an alpha carbon, covalently bonded to a hydrogen atom, a carboxyl group, an amino group, and a variable side chain
• There are 20 amino acids used in protein synthesis, most are synthesised by the body, and 9 are essential and must be obtained through the diet
• Peptide


  Short chains of amino acids
• Peptide bond


  The bond formed between the amino group of one amino acid and the carboxyl group of the next
• Protein Structure Levels


  • Primary
  • Secondary
  • Tertiary
  • Quaternary
• Primary Protein Structure


  The specific order of amino acids in the polypeptide chain
• Secondary Protein Structure


  Regular folding of the polypeptide backbone due to interactions between the peptide bonds, stabilised by hydrogen bonds
• Tertiary Protein Structure


  Further folding due to interactions between the side chains, including weak interactions like hydrogen bonding and ionic bonds, and strong interactions like disulphide bridges
• Quaternary Protein Structure


  Several protein units packing together to form the functional (active) molecule
• Quaternary Protein Structure


  • Haemoglobin (2 alpha subunits + 2 beta subunits)
• Haemoglobin (Hb)


  Functional (active) molecule containing 4 subunits: 2 alpha subunits + 2 beta subunits
• Peptide bond


  The bond between the amino group of a Cysteine and the carboxyl group of a Phenylalanine
• Disulphide bridges in proteins

  • Feature of tertiary structure
• The specific 3D structure is critical for protein function as it enables a protein to recognise and bind specifically to other molecules e.g. hormone + receptor, antibody + antigen, enzyme + substrate
• Enzymes


  Biological catalysts that catalyse (or speed up) reactions