Carbohydrates Flashcards
Isomer
Molecules that have the same chemical formula but a different arrangement of atoms
Difference between glucose’s isomers
The hydroxide group on carbon 1 is flipped by 180 degrees
Maltose
Glucose - glucose
Sucrose
Glucose - fructose
Lactose
Glucose - galactose
Test for reducing sugars
Add Benedict’s reagent to solution
Heat
Blue to brick-red precipitate
Test for non-reducing sugars
If no colour change is observed in initial sugar test
Add HCl to solution and heat
Neutralise solution with sodium hydrogen carbonate
Carry out normal Benedict’s test
Polymer
Large molecule consisting of repeating units, monomers, bonded together
Role of starch
Main storage for glucose in plants due to its
- insolubility (does not decrease water potential of cell, no osmotic effect)
- compactness
Amylose
Linear unbranched molecule with alpha 1,4-glycosidic bonds
Coils into a helix
Used for long term storage as it only has 2 ends
Amylopectin
Chain of alpha glucose monomers joined with 1,4-glycosidic bonds that are cross linked with 1,6-glycosidic bonds
Branched
Used for short term storage as it has lots of ends
So it is easier to break down since lots of enzymes can simultaneously attach
:. Glucose is released more quickly than amylose
Test for starch
Add iodine to food sample
Orange to blue-black precipitate
Cellulose
Long chain of beta glucose monomers joined by beta 1,4-glycosidic bonds that alternate by 180 degrees
Structural polysaccharide in plant walls which prevents osmosis lysis
Cellulose fibres are very strong in tension but also flexible
Chitin
Structural polysaccharide made up of long chains of beta glucose joined together by 1,4-glycosidic bonds that alternate 180 degrees
However, it has a group derived from amino acids to form a heteropolysaccharide
Found in the exoskeleton of insects as it is lightweight but also strong
Glycogen
Main energy store in animals
Structure is identical to amylopectin but branches more often
Stored in the liver and skeletal muscle
