carbs

Question 1

what are carbohydrates made up of

Answer 1

carbon, hydrogen and oxygen

Question 2

what are the functional groups of carbohydrates?

Answer 2

carbonyl group (C=O) and hydroxyl groups

Question 3

what is the molecular formula of glucose?

Answer 3

C6H12O6

Question 4

what is the general formula for monosaccharides?

Answer 4

(CH2O)n where n = 3/4/5/6/7

Question 5

what are 3 important uses of monosaccharides

Answer 5

energy sources to produce ATP during cellular respiration
building blocks to synthesise larger carbs
raw material for synthesis of other organic molecules

Question 6

what are the 2 groups a carbonyl group could be?

Answer 6

aldehyde group (H-C=O) or a ketone group (C=O)

aldehyde groups are easily oxidised to carboxylic acids so do-monosaccharides are strong reducing agents

Question 7

what is an anomeric carbon?

Answer 7

carbon that is bonded to TWO oxygen atoms

Question 8

where does the hydroxyl group bonded to anomeric carbon lie in alpha glucose?

Answer 8

the hydroxyl group lies below the plane of the ring

Question 9

where does the hydroxyl group bonded to anomeric carbon lie in beta glucose?

Answer 9

the hydroxyl group lies above the plane of the ring

Question 10

how are disaccharides formed?

Answer 10

two monosaccharides are joined by a glycosidic bond during a condensation reaction resulting in the loss of a water molecule

Question 11

what is a glycosidic bond?

Answer 11

the bond formed between the anomeric carbon of one sugar unit and another carbon on the other sugar unit

Question 12

what are the TWO ways hydrolysis (break down) of a disaccharide can occur?

Answer 12

1. incubation with dilute acid at 100C
2. incubation with an enzyme

Question 13

what are the monosaccharides that make up maltose, sucrose and lactose?

Answer 13

maltose: glucose + glucose
sucrose: glucose + fructose
lactose: glucose + galactose

Question 14

what monomer is starch made up of

Answer 14

ONLY alpha glucose

starch consists of unbranced amylose and branced amylopectin, both of which are made up of glucose

Question 15

what monomer is amylose made up of and what bond(s) are involved?

Answer 15

alpha glucose
alpha (1,4) glycosidic bonds

Question 16

what is the structure of amylose?

Answer 16

amylose exists as an unbranched chain consisting of many alpha glucose residues joined by alpha (1,4) glycosidic bonds
amylose forms a compact helical structure. there are 6 glucose units per turn in the helix

since amylose is bulky, it is poorly soluble in water and doesn’t exert osmotic influence in the cell

Question 17

what monomer is amylopectin made up of and what bonds are involved?

Answer 17

alpha glucose
alpha (1,4) glycosidic bonds and alpha (1,6) glycosidic bonds

alpha (1,6) glycosidic bonds causes amylopectin to be branched

Question 18

what are the advantages of amylopectin and glycogen being branched?

Answer 18

1. the many branch ends allow a large number of enzymes to act on it at any one time so it is easily hydrolysed
2. extensive branching causes amylopectin and glycogen to be highly compact

Question 19

what monomer is glycogen made up of and what bonds are involved?

Answer 19

alpha glucose
alpha (1,4) glycosidic bonds and alpha (1,6) glycosidic bonds

alpha (1,6) bonds occur more frequently in glycogen than in amylopectin - so glycogen is more compact than amylopectin

Question 20

what monomer is cellulose made up of and what bond is involved?

Answer 20

beta glucose
beta (1,4) glycosidic bonds

Question 21

how is the cellulose polymer formed?

Answer 21

1. cellulose chains run parallel to each other. OH groups project outwards from each chain
2. extensive hydrogen bonds form between the OH groups, establishing rigid cross links between chains
3. the cross-linked cellulose chains associate in groups, forming microfibrils
4. microfibrils associate with other non-cellulose polysaccharides and are arranged in larger bundles, forming macrofibrils

Question 22

what property of cellulose accounts for its high tensile strength?

Answer 22

cellulose fibrils are laid down in different orientations in different layers of the plant cell wall, permitting the cell wall to withstand forces exerted in all directions

Question 23

how does the structure of starch/glycogen relate to its storage function?

Answer 23

1. starch/glycogen is a large molecule and is insoluble, so it does not affect the water potential of cells
2. amylopectin/glycogen molecules are highly branched due to the presence of alpha (1,6) glycosidic bonds, so amylopectin is compact and easily hydrolysed as there are a large number of free ends available
3. amylose molecules are helical in shape, so it is compact
4. (less important) starch/glycogen is composed of several hundreds to thousands of glucose monomers, acting as a large store of carbon
5. (less important) glucose units are linked by alpha (1,4) glycosidic bonds, which are easily hydrolysed by enzymes
6. (less important) anomeric carbon is involved in glycosidic bond formation, making starch/glycogen unreactive and chemically stable

Question 24

how does the structure of cellulose relate to its support function?

Answer 24

1. cellulose is a large molecule and is insoluble, making it a good structural material
2. beta glucose units are linked by beta (1,4) glycosidic bonds, and few organisms produce cellulase which hydrolyses cellulose, so cellulose is stable
3. alternate inverted beta glucose units linked by beta (1,4) glycosidic bonds allow cellulose to form long, unbranched & straight chains, so cellulose provides high tensile strength for structural support