1.4 - Starch, Glycogen + Cellulose

Question 1

What is an e.g. of where starch is found?

Answer 1

• many parts of a plant in form of small grains
• large amounts in seeds + storage organs (e.g. potato tubers)

Question 2

What is starch made up of?

Answer 2

• α-glucose monosaccharides
• linked by glycosidic bonds
• formed by condensation reactions

Question 3

What is the functions of starch?

Answer 3

• energy storage for plants
  - insoluble (doesn’t affect water potential)
  - large so doesn’t diffuse out of cells
  - branches coiled: compact
  - many branch ends = easily hydrolysed/more hydrolysis can occur at same time inc. ROR: releasing more α-glucose more quickly (used readily in respiration)

Question 4

Where is glycogen found?

Answer 4

• in animal + bacteria
• NEVER plant cells

Question 5

What is glycogen made of?

Answer 5

α-glucose monosaccharides

Question 6

What is the function of glycogen?

Answer 6

• energy store for animals, bacteria + fungi
  
  • insoluble: doesn’t affect water potential/diffuse out of cells
  • compact
  • more highly branched than starch (more ends): inc ROR so rapidly broken down to form glucose monomers used in respiration
  • higher metabolic rate as more active than plants

Question 7

What is cellulose made up of?

Answer 7

• β-glucose monosaccharides

Question 8

What is the function of cellulose?

Answer 8

• provides support and rigidity:
  - straight unbranched chains that run parallel + cross linked by hydrogen bonds (add strength)
  - molecules grouped together to form microfibrils: form fibres
• prevents plant cell walls from bursting as water enters by osmosis
  - exerts an inward pressure stopping any further influx of water
  - living plant cells turgid