Biological molecules

• Carbohydrate


  Made of carbon, hydrogen and oxygen.

  A polymer made up of many glucose monomer molecules chemically bonded together by glycosidic bonds. Carbohydrates are in the form of glycogen found in animals or starch found in plants. Glucose is soluble in water. Starch and glycogen are insoluble in water.
• Protein


  Made of carbon, hydrogen, oxygen, nitrogen and sometimes sulfur.

  A polymer made up of many amino acid monomer molecules chemically bonded together in a particular sequence by peptide bonds. There are 20 different amino acids which can be joined together in a vast number of different orders making a huge number of different proteins.
• Lipids


  Made of carbon hydrogen and oxygen.

  A molecule made up of a glycerol and three fatty acid monomer molecules chemically bonded together by ester bonds. Two types of lipids are fats (found in animals) and oils (found in plants).
• Food test for glucose

  Add benedicts reagent to food sample and heat in a hot water bath at 80 degrees Celsius. If benedicts reagent turns from blue to green/yellow/orange/red, glucose is present.
• Food test for starch

  Add iodine solution to the food sample. If the iodine solution turns from orange to blue/black, starch is present.
• Food test for protein

  Add sodium hydroxide (biuret A) to the food solution and mix it. Add a few drops of copper sulfate (biuret B). Do not shake the mixture. If biuret turns from blue to purple, protein is present.
• Food test for lipids

  Add a few drops of ethanol to the food solution and shake. Add an equal volume of water and shake. If a milky-white emulsion forms, fat/lipid is present.
• Enzyme

  A biological catalyst which speeds up the rate of metabolic reactions without being used up.
• Two factors that affect the rate of an enzyme controlled reaction.

  Temperature

  pH
• Why enzymes don't work when the temperature is too high

  The enzymes will start to denature if the temperature is too high. This means the active site will change shape so its shape is no longer complimentary to the substrate and no enzyme substrate complex can form.
• Affect of pH on enzyme function

  Different enzymes work optimally at different pHs. pHs' either side of the optimum pH cause the rate of reaction to be reduced. pHs at the extremes of the optimum pH may cause the enzyme to become denatured.