1.4 Starch,Glycogen and cellulose

Question 1

Describe the structure of starch (amylose)
(3)

Answer 1

• 1,4 glycosidic bonds
• Staright unbranched chain
• It has a helix shape with H- bonds making them more compact

Question 2

Describe the structure of starch (amylopectin)

Answer 2

1,4 and 1,6 glycosidic bonds
Branched = many terminal ends for hydrolysis into glucose

Question 3

Describe the structure of of glycogen
(4)

Answer 3

1,4 and 1,6 glycosidic bonds
Branched= many terminal ends for hydrolysis into glucose
Insoluble= no osmotic effect and does not diffuse out of cell
Compact

Question 4

Describe the structure of cellulose (4)

Answer 4

• 1,4 glycosidic bonds
• Straight, unbranched molecule
• Beta glucose
• Chains are held by many h bonds which forms a fibril

Question 5

What is the basic function of starch

Answer 5

It is an energy store in plant cells

Question 6

What is the basic function of glycogen

Answer 6

Energy store in animal cells

Question 7

What is the basic function of cellulose

Answer 7

Provides rigidity to the plant cell
Prevents the cell from bursting

Question 8

Explain the structure of starch(amylose)
(3)

Answer 8

Helical–> compact for storage in cell
Large,insoluble polysaccharide molecule–>cant leave cell/cross membrane
Insoluble in water–>water potential of cell not affected (no osmotic effect)

Question 9

Explain how the structure of starch(Amylopectin) and glycogen relate to thier functions (4)

Answer 9

• Branched–>more ends for faster hydrolysis –>releases glucose for respiration to make ATP for energy release
• They are compact which fits more molecules in a small area
• Large insoluble molecule–>cant leave cell
• Insoluble in water–> water potential of cell not affected (no osmotic effect)

Question 10

Explain how the structure of cellulose relates to its function

Answer 10

Every other Beta glucose molecule is inverted in a long straight unbranched chain
Many hydrogen bonds link parallel strands to form microfibers
Hydrogen bonds are strong in high numbers so it provides strength to plant cell walls

Question 11

Suggest a method to measure the quanitity of sugar in a solution (3)

Answer 11

• Carry out benedicts test for non recusing sugars
• Filter and dry the precipitate
• Find the mass/weight

Question 12

Suggest another method to measure the quanitity of sugar in a solution

Answer 12

1. Make sugar solutions of known concentrations
2. Heat a set volume of each sample with a set volume of benedicts solution for same time
3. use colorimeter to measure sbsorbance og light of each known conc
4. plot calibration curve-conc on x axis absorbance on y axis and draw a line of best fit
5. repeat benedicts test with unknown sample and measure absorbace
6. read off calibration curve to find concentaruon associated with unknown samples absorbance

Question 13

Describe the biochemical test for starch

Answer 13

Add iodine dissolved in pottasium iodide and shake/stir
positive result= blue black

Question 14

Why does the colour change at the top of the solution first ( during a biochemical test)

Answer 14

Because the molecules that are the hottest are located at the top of the test tube. increases collisions as there are more successful collisions

Question 15

What is a non reducing sugar

Answer 15

A sugar that does not donate an electron to the copper sulphate so it would not change colour