✭ sugars (topic 1, LHR)

• monosaccharides 


  single sugar units with general formula (CH2O)n

  n is the number of carbon atoms in the molecule
• how many carbon atoms do monosaccharides have?

  between three to seven but most common number is 6 carbon atoms
• monosaccharide names/examples


  glucose

  galactose

  fructose
• what are the hexose sugars ?

  glucose, galactose and fructose
• what is a hexose sugar molecule?

  a ring structure formed by five carbons and an oxygen atom

  the sixth carbon projects above or below the ring

  the carbon atoms are numbered starting with 1 on the extreme right
• what do monosaccharides do?

  provide a rapid source of energy

  they are readily abosrbed

  require little or no change before being used in cellular respiration

  glucose and fructose are found naturally in fruits vegetables and honey
• glucose 


  main sugar used by all cells in respiration

  starch and glycogen are polymers made up of glucose subunits joined together

  when starch or glycogen is digested glucose is produced and can then be absorbed and transported in the bloodstream
• galactose 


  occurs in our diet as mainly part of the disaccharide sugar lactose which is found in milk
• fructose 


  sugar which occurs naturally in fruit, honey and vegetables it is a pentose
• disaccharide


  two single sugar units joined together in a condensation reaction
• what is the bond that holds together the two sugar units

  glycosidic bond

  most disaccharides have a 1,4 glycosidic link
• how is a disaccharide formed

  via a condensation reaction releasing a water molecule as the two sugar molecules combine in the reaction
• what are the common disaccharides (found in food)

  sucrose, maltose and lactose
• sucrose 


  glucose + fructose
• maltose 


  glucose + glucose

  disaccharide produced when amylase breaks down starch
• lactose 


  galactose + glucose

  sugar found in milk
• how can the glycosidic link be split in a disaccharide?

  by hydrolysis
• describe how glucose moves into cells by facilitated diffusion

  1. carrier protein in cell surface membrane moves glucose from high to low concentration

  2.happens when glucose binds to carrier protein

  3. carrier protein changes shape to move glucose across the membrane
• Hexose


  A type of carbohydrate with 6 carbon atoms
• Pentose


  A type of carbohydrate with 5 carbon atoms