Biological molecules

• What is a monomer?


  A small, single molecule
• How is a polymer formed?

  By joining many monomers together

  
• What is a condensation reaction?

  Joins 2 molecules and eliminates water
• What does a hydrolysis reaction do?

  Separates 2 molecules by adding water
• What are the two types of reactions involving water in biochemistry?

  • Condensation reaction: joins molecules, removes water
  • Hydrolysis reaction: separates molecules, adds water
• How are carbohydrates classified?

  Into monosaccharides, disaccharides, polysaccharides
• What are monosaccharides?

  Monomers from which larger carbohydrates are made
• Give examples of monosaccharides.

  Glucose, fructose, galactose
• What forms a glycosidic bond?

  A condensation reaction between 2 monosaccharides

  
• What are the isomers of glucose?

  α-glucose and β-glucose
• What is an isomer?

  Same molecular formula, differently arranged atoms
• What is the difference between α-glucose and β-glucose?

  OH group position differs at C1
• What is maltose formed from?

  Glucose + glucose
• What is sucrose formed from?

  Glucose + fructose
• What is lactose formed from?

  Glucose + galactose
• How many carbon atoms does glucose have?

  6 carbon atoms
• What are the examples of polysaccharides?

  • Starch
  • Glycogen
  • Cellulose
• What is the function of glycogen?

  Energy store in animal cells
• What is the structure of glycogen?

  Polysaccharide of α-glucose with branched bonds
• What is the function of starch?

  Energy store in plant cells
• What is the structure of starch?

  Polysaccharide of α-glucose, amylose and amylopectin

  
• What is the function of cellulose?

  Provides strength to plant cell walls
• What is the structure of cellulose?

  Polysaccharide of β-glucose, unbranched chains

  
• How does the structure of glycogen relate to its function?

  Branched for rapid hydrolysis to glucose
• How does the structure of starch relate to its function?

  Helical and compact for storage
• How does the structure of cellulose provide strength?

  Hydrogen bonds link parallel strands

  
• What is the Biochemical test for reducing sugars?

  1. Add Benedict’s reagent
  2. Heat in boiling water bath
  3. Positive: green/yellow/orange/red precipitate
• What is the Biochemical test for non-reducing sugars?

  1. Add dilute hydrochloric acid
  2. Heat in boiling water bath
  3. Neutralise with sodium bicarbonate
  4. Add Benedict’s reagent and heat again
  5. Positive: green/yellow/orange/red precipitate
• What is the Iodine test for starch?

  1. Add iodine dissolved in potassium iodide
  2. Positive: blue-black colour
• What are triglycerides formed from?

  Glycerol and fatty acids
• What bond is formed in triglycerides?

  An ester bond

  
• What is the function of triglycerides?

  Energy storage molecules
• Why are triglycerides insoluble in water?

  They clump together as droplets
• What is the role of phospholipids in cell membranes?

  Form bilayer allowing diffusion of molecules
• What are the properties of phospholipids?

  Polar heads and non-polar tails
• What is the difference between saturated and unsaturated fatty acids?

  Saturated has no C=C double bonds

  
• What is the Emulsion test for lipids?

  1. Add ethanol and shake
  2. Add water
  3. Positive: milky/cloudy white emulsion
• How many common amino acids are there?

  20 amino acids
• What is a dipeptide?

  2 amino acids joined together
• What forms a peptide bond?

  A condensation reaction between 2 amino acids