Carbohydrates

Question 1

difference between a glucose and B glucose

Answer 1

a-glucose: OH group below the plane of the ring
B-glucose: OH group above the plane of the ring

Question 2

structure and properties of monosaccharides

Answer 2

• free C=O group, all reducing sugars
• small in size, have multiple OH groups projecting outwards to form hydrogen bonds with water, soluble in water

Question 3

formation and breaking of glycosidic bond

Answer 3

• joined by glycosidic bonds formed between two monosaccharides with the removal of one water molecule
• can be split into their component monosaccharides via hydrolysis reaction with the addition of H2O molecule, glycosidic bond broken

Question 4

difference in function of glycogen, starch and cellulose

Answer 4

Starch: plant storage polysaccharide
Glycogen: animal storage
Cellulose: plant structural polysaccharide

Question 5

difference in location

Answer 5

starch: chloroplasts
glycogen: liver and muscle cells
cellulose: cell wall

Question 6

difference in monomers

Answer 6

starch and glycogen: a glucose
cellulose: B glucose

Question 7

difference in bonds between monomers

Answer 7

starch: amylose: a(1-4) glycosidic bonds, amylopectin: a(1-4) glycosidic bonds within a branch and a(1-6) glycosidic bonds at branch points

glycogen: a(1-4) glycosidic bonds within a branch and a(1-6) glycosidic bonds at branch points

cellulose: B(1-4) glycosidic bonds

Question 8

difference in orientation of monomers

Answer 8

starch and glycogen: same orientation

cellulose: alternate B glucose monomers rotated 180 wrt each other

Question 9

difference in structure of each molecule

Answer 9

starch: amylose: helical, amylopectin: helical and highly branched
glycogen: helical, more extensively branched than starch
cellulose: long straight chain

Question 10

difference in bonds between molecules

Answer 10

starch and glycogen: no interchain hydrogen bonding
cellulose: interchain hydrogen bonding between cellulose molecules that are parallel to each other –> forming microfibrils

Question 11

how structures of starch and glycogen make them good storage molecules

Answer 11

1. OH groups are involved in interchain hydrogen bonding, cannot form hydrogen bonds with water, insoluble in water, hence does not affect water potential of cells
2. highly branched and many branch ends for hydrolytic enzymes to work on so more glucose molecules can be released rapidly and more ATP molecules can be generated by respiration per unit time
3. they are helical molecules can pack may glucose molecules per unit volume
4. they are large molecules, hence insoluble in water, does not affect wpt of cells

Question 12

how structure of cellulose makes it good structural molecules

Answer 12

• most of the OH groups involved in interchain hydrogen bonding, cannot form hydrogen bonds with water insoluble in water hence does not affect wpt of cells
• alternate B glucose monomers rotate 180 wrt eo to form long straight chains which can form interchain hydrogen bonding with OH groups. projevcting outwards, forming microfibrils –> increases tensile strength
• meshwork of microfibrils creates a porous structure so can distribute osmotic stress in all directions, and is strong and rigid, has a porous structure, and is freely permeable to all solutes