Biological Molecules - Carbohydrates Flashcards
(19 cards)
Elements present in carbohydrates
Carbon, hydrogen and oxygen
General formula of monosaccharides
Cn(H2O)n
Difference between pentose and hexose sugars
Pentose has 5 carbons in the chain, hexose has 6
Example of triose, pentose and hexose sugars
Triose: glyeraldehyde -formed during respiration of glucose
Pentose: Ribose - RNA in nucleotides
Hexose: glucose - all living cells as used in respiration
Fructose - fruit
Difference between alpha and beta glucose
Beta glucose has the hydroxyl group on C1 above the ring
Define isomer
Structurally different but chemically exactly the same - eg. Alpha and beta glucose
General formula of disaccharides
Cn(H2O)n-1
Bond formed in maltose
a 1~4 glycosidic bond
Components and uses of sucrose
a-glucose and fructose
Used for storage as sugar cane or beet and transported in phloem
Components and uses of lactose
a-glucose and galactose
Used- milk sugar as difficult to hydrolyse, providing a slow release of sugars to babies
Components and uses of maltose
a-glucose and a-glucose
Found in intestine and germinating seeds, intermediate in hydrolysis of starch.
Cellulose structure
Beta glucose - therefore forms straight chain as alternate are turned upside down. Hydrogen bonds between cellulose chain form microfibres then macro fibrils and cellulose fibres. Held together with pectins.
Cellulose properties
High tensile strength
Fully permeable to water
Resistant to hydrolysis
Supports a plant when turgid
Glycogen structure
Made up of alpha glucose with more branches than amylopectin and more 1,6 glycosidic bonds making it more compact
Glycogen properties
Insoluble in water Energy storage in animals Similar to amylopectin Hydrolysed very quick to glucose as more 'ends' Storage polysaccharide in animals
Starch structure
Made up of alpha glucose.
Amylose joined by 1,4 glycosidic bond forms helix stabilised by hydrogen bonds
Amylopectin joined by 1,6 glycosidic bonds and so has branched structure
Starch functional points
Insoluble in water Doesn't affect water potential of cells Compact molecule Doesn't diffuse out of cells Ends can easily be broken off for respiration, more in amylopectin so hydrolyses faster
Test for starch
Test with iodine solution, positive results turns blue-black
Hydrolysis
Chemical reaction in which a water molecule is needed to break a complex molecule into small molecules. Can be done with enzymes (eg. maltase) or heating with acid.
