Biological molecules

• What are monomers?


  Small repeating units which make up larger units, called polymers.
• What are polymers? (inc examples)

  Polymers are molecules made from lots of smaller repeating units called monomers.
• What is a hydrolysis reaction?

  Breaks the covalent bond between two monomers, which involves the use of a water molecule.
• What is a condensation reaction?

  Joins two monomers together with the formation of a covalent bond and involves the elimination of a molecule of water.
• What is a monosaccharide?

  Individual sugar molecules (monomers) that make up disaccharides and monosaccharides. All monosaccharides are reducing sugars
• What is a disaccharide?

  Two monosaccharides have joined together through a condensation reaction, forming a glycosidic bond between the two OH groups
• What is maltose?


  A disaccharide of two glucose molecules, formed from the breakdown of starch in germinating seeds.
• What is sucrose?


  A disaccharides formed from glucose and fructose molecules. It is the form in which sugars are transported in the phloem in plants.
• What is lactose?


  A disaccharide of glucose and galactose molecules. It is the sugar found in milk, and provides an energy source for animals.
• What is a polysaccharide?


  A polysaccharide is formed when more than two monosaccharides are joined together by condensation reactions. They can be formed from glucose monomers that are joined by 1-4 or 1-6 glycosidic bonds.
• What is a-glucose?


  A monosaccharide, which is the main substrate for respiration and the form in which carbohydrate is transported. It forms the polysaccharides starch and glycogen.
• What is b-glucose?


  Beta glucose is a monosaccharide which forms the polysaccharide cellulose.
• What is fructose?


  A monosaccharide which is found in nectar, it helps to attract animals for pollination. Fructose and glucose form the disaccharide sucrose
• What is galactose?


  A monosaccharide which, with glucose, forms the disaccharide lactose
• What is the structure of starch?

  Starch is a polysaccharide, made of two types of polymers: amylose and amylopectin.

  Amylose is made from glucose molecules linked by 1-4 glycosidic bonds, they are long unbranched chains held together by hydrogen bonds - this makes them compact and easy to store.

  Amylopectin is made from glucose chains linked together by 1-6 glycosidic bonds, in a branched structure. This increases surface area for enzymes to hydrolyse glycosidic bonds allowing glucose to be released quickly.
• What is the function of starch?

  • main form of carbohydrate in plant cells
  • way of storing excess glucose that is too large to leave cells and it is insoluble (does not affect water potential)
  • can be hydrolysed to release glucose for respiration
• What is the structure of glycogen?

  Glycogen is made of a-glucose molecules bonded by 1-4 glycosidic bonds, but has branched chains bonded by 1-4 glycosidic bonds. The branches increase surface area for enzymes to hydrolyse glycosidic bonds allowing glucose to be released fast. It is also a compact molecule so can be stored easily.
• What is the function of glycogen?

  Glycogen is an energy store as it can be hydrolysed to release glucose quickly. Large quantities can be found in the liver and muscle cells of mammals.
• What is the structure of cellulose?

  • Cellulose is made of long unbranched chains of beta-glucose.
  • Alternate glucose molecules have to rotate so that the H and OH groups on carbon 1 are inverted to form straight chains.
  • The chains are linked together by hydrogen bonds between glucose molecules to form thicker fibres called microfibrils.
  • The glycosidic bonds are 1-4.
• What is the function of cellulose?

  • A major structural component in the cell walls of plants, it provides support and allows cells to be turgid.
  • Microfibrils are very strong and still flexible, due to hydrogen bonds, and this allows them to provide support.
• What is a lipid?

  An organic molecule, that provide a source of energy to help insulate organisms, act as waterproofing and form membranes. Lipids are not polymers.
• What is a triglyceride?

  They are made of a glycerol molecule and three hydrocarbon fatty acid chains (can be saturated or unsaturated).

  There is an ester bond formed by a condensation reaction between each of the three OH groups on the glycerol and the OH group of each fatty acid chain. These bonds can be broken via hydrolysis.