disaccharides

Question 1

what are disaccharides?

Answer 1

two covalently linked monosaccharides formed through condensation

• 1 mono provides hemiacetal in form of anomeric carbon
• 1 mono provides hydroxyl (alcohol)
• reaction produces stable acetal releasing a water molecule

Question 2

mutarotation of disaccharides

Answer 2

terminal glucose can produce free hemiacetal and dynamic equilibrium between alfa and beta structure (free anomeric carbon)

Question 3

what is the configuration of disaccharides based on?

Answer 3

O-glycosidic bond as a configuration (alfa or beta)

Question 4

maltose

Answer 4

alfa(1,4)-glycosidic bond

• several combinations possible
• enzymes direct specific condensation of 2 hydroxyls

Question 5

lactose

Answer 5

found in breast milk

• hydrolysed by lactase in intestine to galactose and glucose
• dose-inducible enzyme-> if the levels are low lactose intolerance develops (disaccaride is not hydrolysed and absorbed, causing the absorption to release harmful chemicals)
• HD milk is pretreated to breakdown lactose

Question 6

sucrose

Answer 6

table sugar

• alfa-D-glucose and beta-D-fructose
• DOES NOT undergo mutarotation

Question 7

describe the mechanism of taste

Answer 7

taste buds in papillae of tongue express different types of taste receptors

• proteins that can bind to substances which depolarise cells and transmit a signal through facial and cranial nerves
• sweet receptors TAS1R2 and TAS1R3 found in palate and in back of tongue
• any molecule that can bind to TAS1 will deliver sweetness sensation (artificial sweeteners bind to receptors and cause sweetness sensation)