AQA A Level Biology

• What are monomers?


  Monomers are small units that are the components of larger molecules.
• Give examples of monomers.


  Examples include monosaccharides, amino acids, and nucleotides.
• What are polymers?


  Polymers are molecules made from many monomers joined together.
• How are monomers joined together?


  Monomers are joined by a chemical bond in a condensation reaction.
• What happens during a condensation reaction?


  A water molecule is eliminated when monomers are joined.
• What is hydrolysis?


  Hydrolysis is when water is added to break a chemical bond between two molecules.
• What elements do carbohydrates consist of?

  Carbohydrates consist only of carbon, hydrogen, and oxygen.
• What is a monosaccharide?


  A monosaccharide is a single monomer of carbohydrates.
• What is a disaccharide?


  A disaccharide is formed by the combination of two monosaccharides.
• What is a polysaccharide?


  A polysaccharide is formed by combining many monosaccharides.
• What type of bond joins monosaccharides in carbohydrates?


  Monosaccharides are joined by glycosidic bonds formed in a condensation reaction.
• What is glucose classified as?

  Glucose is classified as a monosaccharide.
• How many carbon atoms are in a glucose molecule?


  Glucose contains six carbon atoms in each molecule.
• What are the two isomers of glucose?


  The two isomers of glucose are alpha and beta glucose.
• What is the general formula for common monosaccharides?


  The general formula is (CH₂O)_n where n can be any number from three to seven.
• How is maltose formed?


  Maltose is formed by the condensation of two glucose molecules.
• How is sucrose formed?

  Sucrose is formed by the condensation of glucose and fructose.
• How is lactose formed?

  Lactose is formed by the condensation of glucose and galactose.
• What are glycogen and starch formed from?


  Glycogen and starch are formed from many glucose units joined together.
• What type of glucose is glycogen formed from?


  Glycogen is formed by the condensation of alpha glucose.
• What type of glucose is cellulose formed from?

  Cellulose is formed by the condensation of beta glucose.
• What is the main function of glycogen in animals?

  Glycogen is the main energy storage molecule in animals.
• How is glycogen structured?

  Glycogen has a large number of side branches allowing quick energy release.
• Why is glycogen insoluble?


  Glycogen is insoluble, meaning it will not affect the water potential of cells.
• What is starch composed of?

  Starch is a mixture of two polysaccharides called amylose and amylopectin.
• What is amylose?

  Amylose is an unbranched chain of glucose molecules joined by 1,4 glycosidic bonds.
• What is amylopectin?

  Amylopectin is a branched polysaccharide made up of glucose molecules joined by 1,4 and 1,6 glycosidic bonds.
• What are the key properties of starch?


  Starch is insoluble, compact, and releases alpha glucose easily when hydrolyzed.
• What is cellulose's role in plant cell walls?


  Cellulose helps stop the cell wall from bursting under osmotic pressure.
• What are microfibrils?


  Microfibrils are strong threads made of long cellulose chains running parallel to one another.
• How does cellulose contribute to plant turgidity?


  Cellulose exerts inward pressure that stops the influx of water, maintaining turgidity.
• What reagent is used to test for reducing sugars?


  Benedict’s reagent is used to test for reducing sugars.
• What are reducing sugars?


  Reducing sugars are sugars that can donate an electron to Benedict’s reagent.
• What happens when a reducing sugar is added to Benedict’s reagent?


  It forms an insoluble red precipitate (copper (I) oxide) when heated.
• What is the procedure for the Benedict's Test for reducing sugars?


  1. Add 2cm³ of the food sample (liquid form).
  2. Add 2cm³ of Benedict’s reagent.
  3. Heat gently in a water bath for five minutes.
  4. Positive result: solution turns brick red (orange-brown).
• What is the procedure for testing non-reducing sugars with Benedict's reagent?


  Hydrolyze the sample with dilute hydrochloric acid, neutralize, then retest with Benedict's reagent.
• What is the procedure for testing starch with iodine?


  1. Add iodine/potassium iodide to the sample.
  2. Positive result: solution turns blue/black from orange-brown.
• What color indicates the presence of starch in a test?


  A blue/black color indicates the presence of starch.