Biological Molecules


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  • Biological Molecules
    • monomers & Polymers
      • Monomer: a single unit in a polymer
      • Polymer: similar monomers binding together
        • Formed by condensation (removal of water)
          • OH groups bind with water
        • Broken down by hydrolysis (adding water)
    • Food Tests
      • proteins
        • add sodium hydroxide - makes it alkaline
        • then add biuret reagent  (copper (ii) sulphate)
        • if present it will go from blue to purple
      • reducing sugars
        • add benedicts reagent
        • heat it
        • If a positive result  goes blue to orange/ red colour
      • non reducing sugars
        • do the test for reducing sugars
          • get a negative result
        • take a fresh sample & heat with dilute acid
        • Neutralise it with an alkali then test with pH paper
        • add benedicts then heat again
        • Positive result will go from blue to orange/ red
      • lipids
        • dissolve sample in ethanol
        • If a positive result a white emulsion forms
      • starch
        • add iodine dissolved in potassium iodine
        • a positive result - orange to blue black
    • Carbohydrates
      • Mono-saccharide
        • bonded by glycosidic-bonds
        • Joined by condensation  reaction - form poly-saccharides
        • examples:
          • glucose
            • joins with glucose to form maltose
          • fructose
            • Joins with glucose to form sucrose
          • galactose
            • joins with glucose to form lactose
      • Disaccharide
        • 2 mono-saccharides that join together & form glycosidic bonds
        • made by candensation reactions
          • forms a glycosidic bond
          • water is released
        • breaks the glycosidic bond between disaccharides
          • uses water
          • forms two mono-saccharides
      • Poly-sacchqride
        • formed by poly-merisation
        • a large molecule made of many smaller monosaccharides.
        • Starch
          • amylase
            • alpha glucose
            • unbranched
            • coiled structure due to angles of the glycosidic bonds
            • almost cylinder
          • amylopectin
            • alpha glucose
            • branched
            • has side branches
              • allows enzymes to break down molecule - glycosidic bond
            • glucose is
          • Good for storage because
            • doesn't affect water potential
            • branched
            • large - cant' cross cell membranes
            • polymer of glucose - respiration
        • Glycogen (animals only)
          • excess glucose that is stored
          • alpha glucose
          • has loads of side branches
            • stored glucose quickly released
          • very compact
            • good for storage
        • Cellulose
          • unbranched
          • beta glucose
          • forms straight chains
            • joined by hydrogen bonds
              • form strong micro fibils
              • form structural support
    • Lipids
      • Triglycerides
        • 3 fatty acids & 1 glycerol
        • properties
          • insoluble
          • contains a lot of chemical energy
            • makes it good for storage
        • uses
          • storage cells
          • cell membranes
      • Phospholipid
        • 1 clycerol, 2 fatty acids & 1 phosphate group
          • the phosphate & glycerol is hydrophillic
          • fatty acids are hydrophobic
        • can form a phospholipid bilayer
      • Fatty acid
        • can be saturated
          • no double bond
        • can be unsaturated
          • double bond
      • Glycerol
        • can bind with fatty acids
          • forms an ester bond
    • Proteins
      • are made from amino acids
        • can form polypeptides or dipeptides
          • Polypeptide: when 2+ amino acids join together
          • Dipeptide: when amino acids join tigether
          • formed by a condensation reaction
            • forms a polypeptide bond
          • broken by hydrolysis
      • Proteins Shape
        • amino acids in a protein = residue
        • a proteins shape determines its function
          • anti bodies
            • involved in immune response
            • found in the blood
            • amino sequences vary - have variable regions
            • made up of 2 light, short polypeptides & 2 long, heavy polypeptides
          • haemoglobin
            • used for carrying oxygen around the body
            • easy to transport
            • compact and soluble protein
          • transport proteins
            • con tain amino acids which fold up & form chains due to being hydrophillic & hydrophobic
            • transport molecules & ions across the membrane
            • e.g. channel proteins in membranes
          • structural proteins
            • e.g collagen - hair & nails
            • physically strong
            • consits oflong polypeptide chains with parralell crosslinks
            • e.g. keratin - connective tissue
              • 3 polypeptide chains tightly coiled together
                • strong
          • enzymes
            • spherical shape - tightly folded polypeptide chains
            • help synthesise other molecules
            • can be used in digestion
        • Structures
          • Primary
            • a sequence of polypetide chains
          • Secondary
            • poly peptide chain doesnt stay flat
            • hydrogen bonds form  between amino acids
            • forms either and alpha helix or a beta pleated sheet
          • Tertiary
            • more bonds form including hydrogen, ionic & disulfide bridges
              • disulfide bridges
                • amino acids cystiene come cloese together
                • sulphur bonds come together
            • coiled/ folded sheets are coiled/ folded more
          • Quaternary
            • final 3d structure
            • polypeptides assemble together
            • prosthetic bond forms
            • made of multiple polypeptides together
      • Fuctions
        • muscle
        • active transport
        • hormones
        • insulin/ oestrogen
        • membranes
        • haemoglobin
        • contractile
        • transport
        • enzymes
        • Structural
        • immuno-proteins
    • Chroma-tography
      • two main stages
        • staionary phase
          • doesn't move
        • Mobile phase
          • does move
      • Two types
        • gas chromatography
          • a method of separating volatile compounds
          • Process
            • 1) The sample that is going to be tested is first turned into a gas
            • 2) Then it's carried through a column by a nonreactive 'carrier' gas such as helium or other inert gas such as nitrogen.
            • 3) As the sample is carried through the column it is separated into its individual components.
            • 4)  achieve this the column is housed inside an oven, where the temperature is controlled to allow the individual components to exit the column at different times.
          • takes place inside a box - graph chroma-tograph
          • Limitations
            • Potentially, thousands of chemicals may have the same retention time, peak shape and detector response
            • Not all of the substance will be separated and detected
            • Compounds cannot be identified.
      • Chromatography: an analytical technique used to separate compounds within a mixture

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