1.4 Starch,Glycogen and cellulose

Question 1

Describe the structure of starch (amylose)
(4)

Answer 1

• Polysaccharide from alpha glucose
• 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
(3)

Answer 2

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

Question 3

Describe the structure of of glycogen
(3)

Answer 3

• 1,4 and 1,6 glycosidic bonds
• Branched= many terminal ends for hydrolysis into glucose
• Polysaccharide made from alpha glucose

Question 4

Describe the structure of cellulose (4)

Answer 4

• 1,4 glycosidic bonds
• Straight, unbranched molecule
• Chains linked in parallel by hydrogen bonds forming microfibrils
• Polysaccharide of Beta glucose

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 mechanical strength and structural support to the plant

Question 8

Explain the structure of starch(amylose)
(3)

Answer 8

• Helical –> compact for storage in cell
• Large –> cant leave cell surface 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
• Branched so it is more compact- can fit more molecules in small areas
• 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(4)

Answer 10

• Every other Beta glucose molecule is inverted in a long straight unbranched chain
• Many hydrogen bonds link parallel strands to form microfibrils
• 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
• 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