Biological molecules (Mindmap 1)

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  • Biological Molecules
    • Biological molecules are particular groups of chemicals that are found in organisms
    • Bonding and formation of molecules
      • Covalent Bonding
        • Atoms share a pair of electrons in their outer shells
      • Ionic Bonding
        • Ions with an opposite charge attract one another, this electrostatic attraction is known as an ionic bond
      • Hydrogen Bonding
        • The electrons within a molecule are not even distributed but tend to spend more time at one position
          • This region is more negatively charged
            • The molecule is polarised/ is a polar molecule
    • Polymerisation & formation of macromolecules
      • Monomers linked together to form long chains
        • These are called polymers and the process by which they are formed is called polymerisation
    • Condensation and hydrolysis reactions
      • In the formation of polymers by polymerisation, each time a new sub unit is attached a molecule of water is formed
        • Reactions that produce water are condensation reactions
          • Examples: formation of polypeptides from amino acids & formation of the polysaccharide starch from monosaccharide glucose
        • Polymers can be broken down through the addition of water.
          • Water is used to break the bonds that link the sub-units of a polymer, splitting the molecule into its constituent parts
            • This is a hydrolysis reaction
    • Metabolism
      • All the chemical processes in an organism are collectively called metabolism
    • Mole and molar solution
      • Mole is the unit for measuring the amount of a substance
        • One mole contains 6.022 * 10^23 = avogadro's constant
      • A molar solution is a solution that contains one mole of solute in each litre of solution
    • Carbohydrates
      • They are carbon molecules combined with water
        • Carbon very readily forms bonds with other carbon atoms allowing a sequence of carbons to be built at various lengths
          • These form a backbone along which other atoms can be attached permitting a large number of different types of molecule
            • The variety of life on earth is because of organisms being based on the carbon atom
      • The making of large molecules
        • In carbohydrates, the basic monomer unit is a sugar, A.K.A a saccharide
          • A single monomer is called a monosaccharide
            • A pair of monosaccharides combine to form a disaccharide or an even larger combination would be a polysaccharide
              • Examples of disaccharides
                • Glucose + glucose = maltose
                • Glucose + fructose = sucrose
                • Glucose + galactose= lactose
              • When monosaccharides join, a molecule of water is removed so it is a condensation reaction
                • The bond formed is called glycosidic bond.
                • Some disaccharides are reducing sugars so we use the benedict's test
                • Some disaccharides are non reducing sugars so we use Benedict's test but it won't change colour so instead it is as follows: add sample to HCl acid and pace test tube in hot bath , add sodium hydrogencarbonate and test with pH paper that the solution is alkaline, re test by using benedict's and it should turn orange/brown
              • Starch is  polysaccharide
                • Test for starch: change colour of iodine in potassium iodine solution from yellow, t blue/black
                • Starch is made up of chains of a-glucose monosaccharides
                  • The chains may be branched or unbranched
                • The main role of starch is energy storage
                  • It is suited to this because:
                    • It is insoluble and therefore dosen't affect water potential, so water is not drawn into the cells by osmosis
                    • Being large and insoluble, it does not diffuse out of cells
                    • It is compact, so a lot of it can be stored in a small space
                    • When hydrolysed it forms a-glucose which is easily transported and readily used in respiration
                    • The branched form has many ends, which each can be acted on by enzymes simultaneously meaning that glucose monomers are released rapidly
                • It is never found in animal cells. Instead a similar polysaccharide called glycogen serves as the same
                  • Glycogen has a very similar structure to starch but has shorter chains and is highly branched
                    • Its main role is carbohydrate storage.
                      • It is suited to this purpose because:
                        • It is insoluble so does not draw water into cells by osmosis
                        • Insoluble so does not diffuse out of cells
                        • It is compact so  lot can be stored in a small space
                        • It is highly branched so has more ends that can be acted on simultaneously by enzymes so it is more rapidly broken down to form glucose monomers which are used in respiration
              • Cellulose is a polysaccharide
                • It differs from starch and glycogen because it is made of Beta-glucose monomers rather than Alpha
                  • This difference causes a difference in structure and function
                    • Rather than forming a coled chain, cellulose has a straight unbranched chain that run parallel to one another allowing hydrogen bonds to form cross-linkages between adjacent chains allowing there to be strength
                • Cellulose molecules are grouped together to form microfibrils which form fibers
                • It provides rigidity to a plant

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