Biological molecules

• What is a monomer?


  small, basic units units that join up in long chains to make polymers
• Examples of monomers 


  Monosaccharides, nucleotides and amino acids
• What is a disaccharide?

  Two monosaccharides joined together with a glycosidic bond
• Which chemical elements are found in all carbohydrates

  carbon, hydrogen and oxygen
• What type of reaction breaks down disaccharides?

  Hydrolysis reaction
• What is a hydrolysis reaction 


  Breaks a chemical bond between two molecules with the addition of water
• What is a polymer?


  Molecules made up from large monomers joined together
• What is a condensation reaction?

  Joins two molecules together with the formation of a chemical bond + involves elimination of water
• Examples of monosaccharides

  Glucose, galactose, fructose
• Maltose 


  A disaccharide formed by the condensation of two glucose molecules
• Disaccharides 


  Formed by the condensation of two monosaccharides
• A condensation reaction between two monosaccharides form a glycosidic bond
• Sucrose 


  Disaccharide formed by condensation of a glucose molecule and a fructose molecule
• Lactose 


  Disaccharide formed by the condensation of a glucose molecule and a galactose molecule
• How many isomers does glucose have?

  Two. alpha glucose and beta glucose
• Structure of alpha glucose 


  .

  
• Structure of beta glucose 


  .

  
• How is glycogen and starch formed?

  Condensation of alpha glucose
• How is cellulose formed?

  Condensation of beta glucose
• Basic structure of glycogen and function

  • Very compact

  Allows large amount of it to be stored in a small space

  • Side branches
  • so stored glucose can be released quickly
• Basic structure of cellulose and function

  • Provides structural support in cells
  • Long, unbranched chains of beta glucose- linked by Hydrogen bonds to form strong microfibrils
• Amylose ( starch)


  .Long, unbranched chains of alpha glucose.

  .Coiled like structure- allows to be tightly packed

  .Good storage- fit in small space
• Amylopectin (starch)

  • long, branched chains of alpha glucose
  • side branches- allow enzymes to break glycosidic bonds easily+ release stored glucose
• Benedicts test

  • Add excess benedict regent to sample
  • Heat in water bath
  • if +ve, precipitate form
• Describe test for presence of non- reducing sugars

  • Heat sample with dilute HCL
  • Neutralise with NaHCo
  • Carry out beneticts test
• How are triglycerides formed ?

  Formed by three separate condensation reactions

  • Between a glycerol molecule and three different fatty acid molecules
  • ester bond formed between each reaction+ molecule of H2O released
• Test for lipid 


  • Shake substance with ethanol for 1 min
  • Pour in water
  • if present- milky emulsion
• Properties of phospholipid and triglycerides

  Phospholipids

  • Has phosphate group +hydrocarbon tail made of 2 fatty acids

  Triglycerides

  • No phosphate group + 3 fatty acids in its hydrocarbon tail
• General formula of fatty acid

  RCOOH
• Function of Triglyceride 


  Have 3 fatty acids- store energy

  • Insoluble due to hydrophilic tail- good storage as dont effect H2O potential of cell
• Function of Phospholipids 


  Have hydrophilic tail- form double layer with their heads

  • Allows them to form membrane -acts as barrier to H2O substances, can't pass through hydrophobic centre
• Unsaturated fatty acids 


  have at least one double bond in its fatty acid tails
• How to test for reducing sugars

  Beneditcs test
• Test for starch 


  Iodine test
• saturated fatty acid 


  don't have any double bonds in the fatty acid tail
• • in a phospholipid the head is hydrophilic and the tail is hydrophobic
• • triglycerides are energy storage molecules