carbohydrates Flashcards
formula of monosaccharides
CmH2nOn
how to classify monosaccharides
- number of carbon atoms
- location of carbonyl group
- isomerism
how does location of carboxyl group affect carbohydrate
- carbonyl group at beginning of carbon skeleton = aldose (aldehyde sugar)
- carbonyl group in middle of carbon skeleton = ketose (ketone sugar)
how does isomerism affect carbohydrates
- linear or ring structure
- alpha glucose: hydroxyl group below carbon 1
- beta glucose: hydroxyl group above carbon 1
linking of structure to function of monosaccharides
- many hydroxyl groups = able to form polar bonds with water = soluble
- free carbonyl group = gives monosaccharides/sugars reducing ability
- pentoses and hexoses exist as rings = stable bulidings blocks for polysaccharides
- ring structure exhibits alpha and beta isomerism = increase diversisty of monosaccahrides
what are disaccharides + formula + examples
- 2 monosaccharides joined via glycosidic bond with the loss of 1 molecule
- formula: Cn(H2O)n+1
- examples: maltose (2 glucose), , sucrose (fructose + glucose), lactose (galactose + glucose)
how is alpha (1-4) glycosidic bond formed
(present in maltose)
carbon 1 atom of alpha glucose loses OH
carbon 4 atom of alpha glucose loses H
2 alpha glucose joined by O atom of carbon 4
how does benedicts test work
Cu2+ (blue) in alkaline CuSO4 solution is reduced to Cu+ (red) in CuO precipitate by carbonyl (C=O) group
how does acid hydrolysis work (to prove a non-reducing sugar)
- equal volume of sample solution and benedicts solution in a test tube = place in boiling hot water bath
- solution should still remain blue = confirm there is no reducing sugar
- boil new sample with dilute HCl = to hydrolse sugar into components (which should include glucose, a r.s)
- neutralise with sodium bicarbonate and carry out benedicts test agaain
- solution should form brick red ppt = proves it is a non rs
formula and examples of polysaccharides
- formula: (C6H10O5)n
- storage: starch, glycogen
- structural: cellulose
what is starch
- made up of amylose and amylopectin
1. amylose: alpha glucose monomers bonded by alpha (1-4) glycosidic bonds = forms unbrached helical strands (side chains)
2. amylopectin: coiled branched molecule - alpha glucose monomers bonded by alpha (1-4) glycosidic bonds to form helical molecule within a branch
- at branch points: alpha (1-6) glycosidic bonds
testing for starch
yellowish brown iodine dissolved in aqueous potassium iodide = forms soluble linear triodide-ion complex = fits into centre of each turn of amylose helix = forms a blue black starch-iodine complex
what is glycogen
similar in strucute to strach but not ,made up of amylose and amylopectin = evem more extensivly branched
within a branch: alpha glucose monomers bonded by alpha (1-4) glycosidic bonds = forms helical molecule
at branch points: alpha (1-6) glycosidic bonds
- helical branched structure
how does structure of storage polysaccharides relate to their function
- Made up of many glucose monomers = hydrolyses to form many monosaccharides = large energy source in form of ATP
- Comprised of long helical strands = packs many subunits per unit volume = compact energy source = more glucose can be oxidised to release more energy
- starch and glycogen are both branched molecules = more enzymes can work at the same time at end points = higher energy generation per unit time
- Large macromolecule = insoluble in water = will not affect wate rpotential of cells
what is cellulose + how bond is formed
1.beta glucose monomers joined by beta (1-4) glycosidic bond
- The glycosidic bond forms between C1 of one β glucose* monomer and C4 of another β glucose*
monomer; - Condensation* reaction joining two β glucose residues with removal of one water* molecule;
- Reaction is catalysed by enzymes*;
