3.1.2 carbohydrates

Question 2

What are the two isomers of glucose and how are they different?

Answer 2

• alpha and beta glucose
• The hydroxyl and the oxygen are inverted on carbon 1 of beta glucose with the hydroxyl group on top

Question 3

How is glycogen and starch formed?

Answer 3

polysacharides, formed by the condensation of many alpha glucose

Question 4

How is cellulose formed?

Answer 4

A polysaccharide, formed by the condensation of many Beta glucose

Question 5

What is the basic structure and function of glycogen ?

Answer 5

• found in animals
• energy store
• Made of 1-4 and 1-6 glycosidic bonds to form a branched spiral
• branched so that many alpha glucose can be released at a given time
• spiral so it is compact and can store a large amount in a small space

Question 6

What is the basic structure and function of starch?

Answer 6

• found in plants
• energy store
• amylose: made of only 1-4 glycosidic bonds to form an unbranched spiral shape
• less soluble than amylopectin and slower to break down
• amylopectin: made of 1-4 and 1-6 glycosidic bonds to form a branched spiral structure
• branched so that many alpha glucose can be released at a given time
• spiral so it is compact and can store a large amount in a small space
• insoluble so doesn’t affect water potential

Question 7

What is the basic structure and function of cellulose?

Answer 7

• found in plants
• Made of 1-4 glycosidic bonds where every other Beta glucose is flipped 180 degrees to form a straight unbroken chain
• The straight chains form together via hydrogen bonds to form microfribrils and eventually macrofibrils
• It’s functions include: structural support, barrier to pathogens and water regulation
• On mass the hydrgoen bonds creates a strong structure
• Microfibrils provide strength for the upright growth of plants
• cellulose forms cell walls
• The straight unbroken chains of cellulose provide rigidity which helps regulate water movement in the plant

Question 8

What is the bio-chemical test for reducing sugars?

Answer 8

• add benedicts solution to crushed and filtered food sample
• place in a hot water bath for 5 minutes
• positive result: green, yellow and red

Question 9

What is the biochemical test for non-reducing sugars?

Answer 9

• Add hydrochloric acid to crushed and filtered food sample and then heat
• Make the solution alkiline
• add benedicts and heat solution again
• positive result: green, yellow and red

Question 10

What is the biochemical test for starch?

Answer 10

• Add iodine to crushed and filtered food sample
• positive result: blue/black