Biological molecules

• Water has a high specific heat capacity.
• Water has a high surface tension because of cohesion between water molecules which forms a ‘skin’ on the surface.
• Adhesion - hydrogen bonding causes molecules to stick to other polar molecules.
• Ice is less dense than water and provides a habitat for some organisms.
• The biological significance of ice being less dense than water is that ice floats which provides habitats on the surface, it insulates bodies of water which prevents freezing.
• A dipole is a molecule with a positive and negative end.
• Monosaccharides are small organic molecules with the formula (CH2O)n.
• Glucose is a hexose sugar which means it contains 6 carbon atoms.
• An isomer is a molecular with the same chemical formula with a different structure.
• When two monosaccharides react together, the reaction is called a condensation reaction.
• Examples of monosaccharides are glucose, fructose and galactose.
• A glycosidic bond is a bond that joins two glucose molecules together through oxygen.
• Starch is a glucose storage molecule.
• Cellulose is used for structure.
• Starch is branched.
• Cellulose is linear.
• Lipids are broken down into fatty acids and glycerol.
• COOH is a carboxyl group.
• Unsaturated fatty acids have a double bond in them.
• The bond in a triglyceride is an ester bond.
• A triglyceride is made up of a glycerol molecule and 3 fatty acid molecules.
• Hydrolysis reactions split ester bonds.
• Condensation reactions form ester bonds.
• LDL is a low-density lipoprotein and if there is a high level of it in your body, it increases risk of heart disease or strokes.
• HDL are high-density lipoproteins that absorbs cholesterol from the blood, carries it to the liver where the liver flushes it. A high level of this lowers health risks like heart disease.
• Sources of saturated fats are fatty cuts of meat, butter, chocolate, cake, etc.
• Sources of unsaturated fat are nuts, seeds, fish, olives, etc.
• There are 20 different types of amino acids - 10 which are essential and 10 which are non-essential.
• The general structure of an amino acid is a central carbon and hydrogen, a carboxyl group (COOH), an amine group (NH2) and a variable side chain or ‘R’ group.
• Carboxyl groups and amino groups in amino acids can form charges which means it is slightly polar.
• The primary structure is the sequence of amino acids in a polypeptide and the bonds involved are peptide bonds.
• The secondary structure is the presence of an alpha helix or a beta-pleated sheet and the bonds involved are hydrogen bonds.
• A polymer is a large molecule made up from many smaller molecules called monomers.
• A dipeptide is two amino acids joined together by a peptide bond.
• The sequence of amino acids determines bonding between R groups and R groups determine the shape of the protein.
• Hydrophobic means repelled by water and these are non-polar.
• Hydrophilic means attracted to water and these are polar or ionic.
• The tertiary structure is the three dimensional shape of the polypeptide. The bonds involved are disulphide bridge, ionic bonds, hydrogen bonds and hydrophilic and hydrophobic interactions.
• The quaternary structure is more than one polypeptide chain joined together by bonding between R-groups. The bonds involved are disulphide bridge, ionic bonds and hydrogen bonds.
• Fibrous proteins are long, thin chains of amino acids which are insoluble in water.