Lipids, carbohydrates and proteins

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  • Lipids
    • Lipids are insoluble in water, but are soluble in some organic solvents
      • Polar molecules dissolve in water
    • Lipids are made of hydrogen, oxygen and carbon
      • These are known as hydrocarbons
        • The formula for a lipid is...CH3 (CH2)n COOH
    • Triglycerides are made of 3 fatty acids, and a glycerol back bone
      • The fatty acids join to the glycerol by an ester bond
        • Ester bonds cause the triglyceride to create 2 more water molecules
    • Lipids are stored in adipose tissues
      • This is loose connective tissue
    • In phospholipids the glycerol backbone joins with 2 fatty acids and one phospholipid
      • This causes the head to be Hydrophilic, and the tail to be hydrophobic making them useful in membrane structures
  • Carbohydrate
    • Carbs are broken down by carbohydrase in the ileum
    • Carbs are used as both an energy source and structural materials
    • They are made up of Carbon, Hydrogen and Oxygen
      • Carbon bonds very easily, so monomers of carbs quickly form di/poly saccharides
    • Mono- saccharides are simple sugars with the formula...(CH2O)n
      • Di-saccharide are formed when 2 monomers join together to form a 'double sugar'
        • Poly- saccharides are large molecules made from many monomers
    • Glucose can be represented in the form of a ring
      • There are 2 forms of glucose, alpha and beta, and their structures are slightly different
        • The Carbon 1 has the OH and the H swapped around for different forms
          • Learn this difference in stucture
        • The different forms are known as structural isomers
    • fructose is very soluble and is found in many fruits
    • Galctose is less soluble and is used in the production of glyco- proteins/lipids
    • Pentose sugars have 5 carbon atoms, these include DNA and RNA
      • Learn the structure of DNA and RNA
    • Poly and Di saccharides need to be broken down by hydrolysis before they are absorbed
      • Amylase breaks these large saccharides into monomers for digestion
        • Amylase breaks down starch and maltose into glucose
  • Proteins
    • Proteins are made up of chains of Amino Acids
    • Proteins have numerous roles within the body
      • Structural proteins are used for tissues, skin and muscle etc.
      • Enzymes speed up reactions inside the body are known as catalytic proteins
      • Signaling proteins include hormones and receptors
      • Antibodies are immunological proteins
    • Proteins contain an amino group, a carbolic acid group and an R group
      • The R group is the only part of the structure that changes
    • Di-peptides and poly-peptide are formed when 2 monomers join together using condensation reactions to form a peptide bond
      • When 2 amino acids join together the bond between the carbolic and the amino group is a weak ionic bond
    • There are 4 levels of structure in proteins
      • Primary structure
        • Secondary structure
          • Tertiary structure
            • Quaternary structure
              • 2 or more polypeptide chains join together
            • a 3D shape is formed and the protein is highly folded
          • Alpha Helix or beta pleated sheet is formed due to folding
        • This is an Amino acid
    • Cystine has an R group that is sulfur (S), when 2 of these join together at the R group they form a DI-sulphide bond
    • Fibrous proteins are formed by parallel polypeptide chains held together by cross links
      • Collagen is a fibrous protein and is used in connective tisissues
      • Keratin is the main component of hair and nails
    • Globular proteins are highly folded into spherical shapes with hydrophobic parts on the inside and hydrophilic parts on the outside
  • Tests
    • Benedict's test for non-reducing sugar
      • Boil solution with HCl and then add sodium hydro carbonate
        • Follow Benedict test for reducing sugars to rue out this possibility
    • Benedict test for reducing sugars
      • Add Benedict's solution and heat, brick red colour indicates sugar present
    • Emulsion test for lipids
      • shake with ethanol then add to water, milky precipitate indicates lipids
    • Biuret test for proteins
      • Add sodium hydroxide, then Copper (II) sulphate to the solution, if the solution goes purple proteins are present

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