2.2.3 carbohydrates 1: sugar Flashcards
- monosaccharides - disaccharides
carbohydrates
group of molecules containing carbon, hydrogen & oxygen
glycosidic bond
bond formed between 2 monosaccharides by condensation
reaction
in a carbohydrate atom, how many hydrogen/oxygen atoms are there for every 1 carbon
hydrogen = 2
oxygen = 1
what do carbohydrates act as? (give examples)
- source of energy eg. glucose
- store of energy eg. starch, glycogen
- structural units eg. cellulose (plants), chitin (insects)
3 main groups of carbohydrates
- monosaccharides
- disaccharides
- polysaccharides
characteristics of monosaccharides
- lots of C-H bonds = source of energy
- sugars (sweet)
- soluble in water
- insoluble in non-polar solvents
- exist as straight-chains, ring or cyclic forms
what does the backbone of monosaccharides consist of
single-bonded carbon atoms with 1 double-bonded to oxygen atom (carbonyl group)
different sugars can have different numbers of carbon atoms:
hexose = 6
pentose = 5
triose = 3
monosaccharide hexose sugar are monomers of more complex carbohydrates
what do they bond together to form
disaccharides or polysaccharides
example of monosaccharide hexose sugar
glucose
in a solution, which sugars exist as straight chains
triose & tetrose sugars
which sugars are more likely to be found in ring/cyclic form (in solution)
pentose & hexose sugars
in the straight chain form, explain the isomer of glucose
-OH & -H are reversed
in ring shape form, what are the 2 isomers of glucose
alpha & beta glucose
- the -OH & -H can be above or below plane of ring
describe disaccharides
- sweet
- soluble
most common disaccharides
- maltose
- sucrose
- lactose
which 2 disaccharides are reducing sugars
maltose & lactose
which disaccharide is a non-reducing sugar
sucrose
2 monosaccharides bonded for maltose
alpha glucose + alpha glucose
2 monosaccharides bonded for sucrose
alpha glucose + fructose
2 monosaccharides bonded for lactose
beta galactose + alpha glucose
2 monosaccharides bonded for cellobiose
beta glucose + beta glucose
what happens when 2 monosaccharides join
- condensation reaction occurs
- forms a glycosidic bond
- 2 hydroxyl groups line up alongside one another (water molecule removed)
- oxygen atom acts as link between 2 monosaccharide units
how are disaccharides broken into monosaccharides
- via hydrolysis reaction (requires + of water)
- water provides hydroxyl group & 1 hydrogen which helps glycosidic bond to break
