Topic 13: carbohydrates Flashcards
(12 cards)
General formula of carbohydrate
- Cn(H2O)n
Define monosaccharies
- Consist of 1 single polyhydroxy aldehyde/ketone
Explain the formation of 2 cyclic forms of D-glucose
- C1 carbon atom = anomeric carbon
- ɑ and ß forms = anomers
- Equilibrium mixture = 1/3 ɑ + 2/3 ß + 1% open chain
- C1 + C5 interact = create ring
- Mutarotation = process where anomers interconvert in aq solution
Compare Fischer + Haworth projections
- Fisher = Hydroxyl groups on right of skeleton
- Haworth = down
Give epimers of glucose
- Mannose = at C2
- Galactose = at C4
Give the different conformations of rings
- B-D glucose = chair + boat
- B-D ribose = envelope
Describe reducing sugars
- Sugar that acts as reducing agent
- Free aldehyde + ketone group
- E.g. glucose + fructose + galactose
- React with Cu2+ ions = reduced to Cu+
- Glucose oxidized = gluconic acid
Describe Fehling’s solution
- Test for presence of reducig sugar
- Detect high glucose levels in blood/urine = diagnose diabetes
Describe glucose meter
- Use enzyme glucose oxidase
- H2O2 = couples to colored compound = measured
- Glucometer = use electrode instead of O2 = current in proportion to glucose concentration
Give examples of disaccharides
- Lactose
- Maltose
- Sucrose
Give examples of linkage between monosaccharides
1) Disaccharides
- Lactose = B galactose + B glucose via B 1-4
- Maltose = a/B glucose via a 1-4 glycosidic
- Sucrose = a glucose + B fructose via a 1-2
2) Oligosaccharides + polysaccharides = 2+ = O-glycosidic bonds
- Cellulose = D-glucose via B 1-4
- Amylose = linear a-D-glucose via a 1-4 = in starch
- Glycogen = branched a-D-glucose via a 1-4/1-6 = storage in liver/muscles
- Chitin = linear homopolysaccharide N-acetylglucosamine via B 1-4 = exoskeleton
Decribe the hydrolysis of dietary polysaccharides
- Starch broken down
- Salivary α-amylase = hydrolyzes internal α1-4 = short fragments
- Pancreatic α-amylase = maltose/maltotriose + dextrin + amylopectin 1-6 branch
- Intestinal brush border = maltose + dextrin degraded to glucose
- Enzymes on intestinal epithelial cells = hydrolyze disaccharides + dextrins
