topic 4 past paper questions

• what is the monomer that makes up cellulose

  beta glucose
• how are monomers held together in a cellulose molecule

  by glycosidic bonds in a branched chain
• where is calcium pectate

  middle lamella
• difference between chitin and cellulose molecule

  both contain glycosidic bonds

  both have every other monomer inverted

  monomer of chitin has 8 carbon atoms while cellulose has 6 atoms

  chitin has additional side chain and nitrogen while cellulose does not
• similarities between structure of cellulose and amylopectin

  both are polysaccharides

  both contain 1,4 glycosidic bonds
• difference between amylopectin and starch structure

  amylopectin is branched cellulose is not

  amylopectin has 1,6 glycosidic bonds while cellulose does not
• difference between hexose in cellulose and hexose in amylopectin

  amylopectin contains a-glucose and cellulose contains b-glucose
• what is the name of the bond between adjacent cellulose molecules in a cellulose microfibril


  hydrogen
• why does seedling need magnesium ions

  magnesium needed to make chlorophyll ions

  chlorophyll ions required for photosynthesis
• name a plant tissue that has lignin in its cell walls

  xylem or sclerenchyma
• explain the role of the middle lamella when a plant completes mitosis

  middle lamella is produced between adjacent new cells because the middle lamella holds cell walls together
• plasmodesma

  cytoplasmic conncetion between cells which allows transport or communication between cells
• explain the effects of a shortage of magnesium ions on a plant

  -shortage of magnesium ions limits the production of chlorophyll

  lack of chlorophyll causes lack of photosynthesis

  lack of photosynthesis means lack of glucose and carbohydrates

  therefore plant leaves may be yellow or small
• give two reasons why a sieve tube element does not require rough endoplasmic reticulum and ribosomes

  there will be no transcription/mRNA therefore ribosomes are not required for translation

  and there will be no proteins synthesised to be processed in the endoplasmic reticulum
• describe the structure of starch

  -polysaccharide made from alpha glucose

  -monomers in the chains are joined by 1,4 glycosidic links

  -starch contains unbranched chains of amylose and branched chains of amylopectin

  -branches are joined to chains by 1,6 glycosidic links
• explain why starch must be broken down before it can be used by the cells of the growing plant

  to produce glucose or maltose which is soluble and enter cells easily, and then be used in respiration
• what is tensile strength

  the pulling force the fibre can withstand before breaking
• explain how the structure and properties of starch are related to its function as a storage molecule

  1. contains gluclose needed for respiration and energy
  2. insoluble so it has no osmotic effect and remains in the cell
  3. amylose is coiled, making starch compact so more can be stored
  4. amylopectin is branched and contains 1,6 glycosidic bonds so it is rapidly hydrolysed
• describe the positions in the stem of those tissues that contain lignin

  sclerenchyma fibres on the outside of the vascular bundle

  xylem vessels on the inner side of the vascular bundle
• describe the importance of magnesium ions in the production of PLANT FIBRES

  -essential to produce chlorophyll

  • chlorophyll is necessary to produce glucose during photosynthesis
  • and glucose is needed to produce cellulose for cell walls
• describe the arrangement of glucose monomers in a cellulose molecule


  monomers are conncted by 1,4 glycosidic links and alternate monomers are inverted
• starch can be broken down by a

  hydrolysis reaction involving glycosidic bonds
• explain how the structures of amylopectin and glycogen make them suitable for storing energy

  -both branced therefore can be rapidly hydrolysed to release glucose

  • are compact so more energy can be stored
  • insoluble therefore does not affect osmosis
  • molecules too large to diffuse across cell surface membrane and remain in cells
• glycogen

  1,4 and 1,6 glycosidic bonds , branched