carbohydrates Flashcards
name the 3 monosaccharides
- glucose
- fructose
- galactose
name the 3 disaccharides and what they are composed of
- maltose = glucose + glucose
- lactose = glucose + galactose
- sucrose = glucose + fructose
name the 3 polysaccharides
- starch
- cellulose
- glycogen
what are the bonds between amino acids called?
peptide bonds
what is a hydrolysis reaction?
a reaction that breaks larger molecules into smaller ones using water molecules
what is a condensation reaction?
a reaction that joins molecules together with the release of water molecules
all monosaccharides are what type of sugars?
reducing sugars
what is the method for testing for reducing sugars?
1) Place the sample in a boiling tube (must be a liquid sample).
2) Add an equal volume of benedicts reagent (copper ii sulfate).
3) Heat the mixture in a boiling water bath for 5 minutes.
4) positive result= brick red precipitate is formed
what is the method for testing for non-reducing sugars?
1) (from doing the test for reducing sugars) the solution will remain blue, indicating a negative result.
2) add dilute HCl to the solution and boil.
3) add benedicts solution and the mixture should then give a positive result
what ratio do carbohydrates appear in?
Cx(H2O)y
what are the 2 pentose monosaccharides?
- ribose = sugar in RNA molecules
- deoxyribose = sugar in DNA molecules
what are the 2 polysaccharides that make up starch?
amylose and amylopectin
what are the structure and properties of amylose?
- Alpha-glucose molecules joined by only 1,4 glycosidic bonds
- bond angle means the chain twists and forms a helix which is stabilised by hydrogen bonding.
- this makes amylose compact and not very soluble
- not a branched structure
what are the structure and properties of amylopectin?
- insoluble, branched, compact
- alpha-glucose molecules mainly joined by 1,4 glycosidic bonds, but some 1,6 glycosidic bonds
- this creates a slightly branched structure which forms a helix
- can release glucose slightly quicker because it has more ends than amylose
what are the structure and properties of glycogen?
- insoluble, branched, compact
- 1,6 glycosidic bonds every 10 molecules
- forms many branches and is very compact and ideal for storage
- the free ends speed up the process of storing and releasing glucose molecules required in the cell (this is better for animals as we need more energy)
what are the structure and properties of cellulose?
- made of beta-glucose molecules
- they form a polymer by every other glucose molecule rotating 180 degrees
- this means the OH groups on both the molecules are then close enough to form a 1,4 glycosidic bond
- this does not coil or form any branches
explain how cellulose molecules join together to form cellulose fibres
- chains of beta glucose molecules are parallel and linked together by hydrogen bonds and form microfibrils
- parallel microfibrils join together to form macrofibrils
- macrofibrils combine to produce cellulose fibres.
what are important properties of cellulose fibres?
- strong and insoluble and used to make cell walls
- this means it is hard to break down and forms the fibres necessary for a healthy digestive system
- the wall is fully permeable
what is the method for testing for reducing sugars?
- use benedicts reagent (copper II sulfate)
method - place the sample in a boiling tube (liquid form)
- add an equal volume of benedicts reagent
- heat the mixture in a water bath for 5 minutes
- a brick red precipitate should form if a reducing sugar is present
what is the method for testing non-reducing sugars?
- (presuming a negative result for the reducing sugar test)
- boil the solution with dilute HCl
- add benedicts solution, this should then give a positive result
(in the case of sucrose or other molecules it is usually that they ar hydrolised into their reducing sugar monomers)
