carbohydrates

Cards (57)

  • amylose is an unbranched polysaccharide made up of alpha glucose monomers joined by a 1,4 glycosidic bonds that also make up starch
  • amylopectin is a branched polysaccharide made up of alpha glucose monomers joined by a 1,6 and 1,4 glycosidic bonds that also make up starch
  • cellulose is a linear polysaccharide that is the main component of the cell wall in plants and is made up of many beta glucose molecules joined by b-,1-4 glycosidic bonds
  • examples of monosaccharides are glucose, galactose ,fructose, deoxyribose and ribose
  • examples of disaccharides are lactose, maltose and sucrose
  • polysaccharide examples are glycogen, cellulose and starch
  • glucose is the major energy for most cells
  • glucose is highly soluble and is the main form in which carbohydrates are transported around the body of animals
  • glucose exists in different forms called structural isomers
    2 common isomers are alpha glucose and beta glucose
  • in alpha glucose the position of the H is above the carbon
  • in beta glucose the H is below the carbon1
  • 2 monosaccharides react in a condensation reaction to form a disaccharide
    one molecule of water is eliminated per bond and a glycosidic bond forms
  • test for non-reducing sugars:
    • The addition of acid will hydrolyse any glycosidic bonds present in any carbohydrate molecules
    • The resulting monosaccharides left will have an aldehyde or ketone functional group that can donate electrons to copper (II) sulfate (reducing the copper), allowing a precipitate to form
    • To test for the presence of starch in a sample, add a few drops of orange/brown iodine in potassium iodide solution to the sample
    • The iodine is in potassium iodide solution as iodine is insoluble in water
    • If starch is present, iodide ions in the solution interact with the centre of starch molecules, producing a complex with a distinctive blue- black colour
  • The iodine test for starch is useful in experiments for showing that starch in a sample has been digested by enzymes
  • glucose can be used in aerobic respiration to produce ATP
  • carbohydrates only contain carbon, oxygen and hydrogen
  • monosaccharides have the general formula CnH2nOn
  • due to the inversion of b - glucose molecules, many hydrogen bonds form between the long chains giving cellulose its strength
  • what is the method for testing for non reducing sugars?

    add 2cm3 of the food sample being tested to 2cm3 of Benedict's reagent in the test tube and filter
    then place the test tube in a water bath for 5 minutes (no colour change)
    add 2cm3 of hydrochloric acid in a test tube to food sample
    gradually add hydrogencarbonate to the test tube to neutralise , as Benedict's reagent doesn't work in acidic conditions
    test with PH paper to check solution is alkaline
    add 2cm3 of Benedict's reagent and boil in water bath for 5 minutes
    positive result: orange to brown
  • glucose + fructose -> sucrose
    <-
  • glycosidic bonds form between disaccharides
  • amylose is coiled and compact, whereas amylopectin is highly branched
  • starch is insoluble so doesnt't affect water potential
  • starch is insoluble so doesnt diffuse into cells
  • cellulose is made up of beta glucose rotated at 180 degrees
    it is straight and unbranched
    individual hydrogen bonds and some (little) strength to the molecule
  • cellulose group together to form microfibrils to form fibres, which provides more strength
  • what are 3 characteristics of monosaccharides?
    sweet tasting
    soluble
    forms crystals
  • most biological polymers are formed from their monomers via condensation reactions
    in a condensation reaction:
    • 2 monomers are joined together
    • a water molecule is eliminated
    • a chemical bond is formed e.g a glycosidic bond
  • the hydroxyl groups (-OH) of carbohydrates is polar and makes the molecule soluble in water
    the greater the number of free hydroxyl groups as a proportion of the number of carbon atoms, the more soluble the carbohydrate
  • sucrase is the enzyme that breaks down sucrose
    it breaks down glycosidic bonds
  • a hydrolysis reaction occurs in the break down of sucrose producing the monosaccharides fructose and glucose
  • to form cellulose the condensation polymerisation of beta glucose molecules molecules
  • amylopectin contains 1,4 and 1,6 glycosidic bonds between alpha glucose monomers
    it contains 1,4 bonds between two glucose units in the straight chains and a 1,6 bonds at the branching
  • alpha glucose undergoes condensation polymerisation to form amylopectin, which can be hydrolysed back into alpha glucose monomers
  • in isomaltulose what is the bond that holds the alpha glucose and fructose together?
    1,6 -glycosidic bond
  • carbohydrase enzyme digests carbohydrates such as
    using the iodine test you can see if starch has been digested by the digestive enzyme if the colour changes from blue-black to yellow/orange
  • the monomer in cellulose is beta glucose
  • glycosidic bonds join monosaccharides together