Complex carbohydrates

Question 1

What are the sources of complex carbohydrates (2)

Answer 1

1. plant sources
2. animal meat

Question 2

What are the complex carbohydrates ‘polymers’ of sugars (2)

Answer 2

1. homoglycans/homopolysaccharides - simpler structures - one type of sugar units
2. heteroglycans/heteropolysaccharides - more complex - various sugar units and glycose derivatives repeating units present.

Question 3

What are the functions of complex carbohydrates (5)

Answer 3

1. Storage - starch, glycogen
2. structural - cellulose, chitin
3. protective - hyaluronic acid (connective tissue)
4. cellular recognition - blood group systems
5. specific agents - heparin (anti-coagulant)

Question 4

Complex carbohydrates structure and name (3)

Answer 4

1. Alpha glucose - Axial OH (downwards)
2. Beta glucose - Equatorial OH (upwards)
3. Name alpha/beta then numerically from the axial/equatorial OH depending on the carbon the bond is on

Question 5

What is the structure of amylose (3)

Answer 5

1. linear chains of glucose of varying chain length
2. glycosidic linkages are a (1→4)
3. These linkages promote a helix structure in which hydrogen bonds form between the oxygen bound at the 2 carbon of one glucose and the carbon 3 of the next glucose.

Question 6

How are complex carbs metabolised (2)

Answer 6

1. disaccharides → monosaccharides
2. via glycoside hydrolases

Question 7

How is amylase metabolised (2)

Answer 7

1. salivary alpha-amylase in animals (endoamylase) splits alpha(1→4) glucosidic linkages
2. beta-amylase in plants and microorganisms (exoamylase) cleaves disaccharide units from the non-reducing end of chains to form dimers of maltose units

Question 8

What is cellulose (5)

Answer 8

1. found in cell walls of plants
2. linear polymer of glucose beta (1→4) linkages
3. hydrogen bonding provides strength
4. chemically inert, resistant to hydrolysis by digestive tract amylases in humans
5. requires cellulase - a bacterial beta-glucoside which enables digestion by ruminants e.g. cows

Question 9

What is Microcrystalline cellulose (5)

Answer 9

1. found in cell walls of plants
2. microcrystalline cellulose (MCC) is a term for refined wood pulp
3. texturiser, and an anti-caking agent
4. fat substitute, emulsifier, filler and diluent
5. extender, bulking agent in food production

Question 10

What is glycogen (6)

Answer 10

1. major form of energy source in animals
2. found in the liver and muscles
3. highly branched glucose chains
4. branches every 8-12 glucose units
5. liner linkages - alpha(1→4)
6. branch linkages - alpha(1→6)

Question 11

How is glycogen metabolised (4)

Answer 11

1. in muscles & liver
2. Hydrolysed by Glycogen phosphorylase to release glucose-1-phosphate.
3. Insulin (a hormone) stimulates conversion of glucose to glycogen
4. Glucagon (a hormone) stimulates conversion of glycogen to glucose

Question 12

What are heteroglycans (4)

Answer 12

1. Heteroglycans in nature contain other sugars with an anomeric centre
2. alpha-glucose (pytanose form)
3. alpha-galactose (pyronose form)
4. alpha-mannose (pyranose form)

Question 13

What are acylated aminoglycan molecules (3)

Answer 13

1. Important acylated aminoglycan molecules are with an anomeric centre: (often found in glycoproteins)
2. N-acetylglucosamine
3. N-acetylgalactosamine

Question 14

What is chitin