Polysaccharides - Lesson 2 Flashcards
what is an oligosaccharide
molecules with 3-10 monosaccharide units
what is hydrolosis
a reaction in which bonds are broken by the addition of a molecule of water
what is amylose
a complex carbohydrate containing only glucose monomers joined together by 1,4-glycosidic bonds so the molecules form long unbranched chains
what is amylopectin
a complex carbohydrate made up of glucose monomers joined by both 1,4-glycosidic bonds and 1,6-glycosidic bonds so the molecules branch repeatedly
what is glycogen
made up of alpha-glucose units joined by 1,4-glycosidic bonds but also has 1,6-glycosidic bonds, giving it many side branched
what is cellulose
a complex carbohydrate with beta-glucose monomers held together by 1,4-glycosidic bonds. It is important in plant cell walls
what are 3 characteristics of polysaccharides structure that makes them ideal storage molecules
- can form compact molecules, so large numbers can be stored in a cell
- glycosidic bonds are rapidly broken, allowing fast release of monomers for cellular respiration
- are not soluble in water, so have little effect on water potential and cause no osmotic water movement
what is starch used as
an energy store in plants
what is the function of amylopectin
releases glucose rapidly for cellular respiration
what is the function of amylose
releases glucose more slowly
what is glycogen used as
a carbohydrate energy store found in animals and fungi
describe the structure of cellulose
beta-glucose are held together by 1,4-glycosidic bonds. Cellulose contains cross-linking and it holds neighbouring chains firmly together
what does cross-linking mean in cellulose
the linking of beta-glucose molecules means the hydroxyl group sticks out. This means hydrogen bonds form between the partially positive hydrogen atoms of the hydroxyl groups and the partially negative oxygen atoms in other areas of the glucose molecules
why can most animals not digest cellulose
most animals do not possess the enzymes needed to break the 1,4-glycosidic bonds between the molecules of beta-glucose and so they cannot digest the cellulose
where does hydrolysis take place
takes place in the gut, and in the muscle and liver cells when the carbohydrate stores are broken down to release sugars for cellular respiration
describe the structure of amylose
amylose is an unbranched polymer. It is purely made up of alpha-glucose molecules joined by 1,4-glycosidic bonds. As the chain lengthens, the molecules spirals, which makes it more compact for storage
describe the structure of amylopectin
amylopectin is a branched polymer. It contains 1,4-glycosidic bonds and few 1,6-glycosidic bonds. The branched chain has many terminal glucose molecules, which can be broken off rapidly when energy is needed
describe the structure of glycogen
glycogen is made up of many alpha-glucose molecules, joined by 1,4-glycosidic bonds and many 1,6-glycosidic bonds. Thus, glycogen can be broken down rapidly
compare and contrast the structures of starch and cellulose
- starch is made up of many alpha-glucose molecules joined together by 1,4 and 1,6-glycosidic bonds, whilst cellulose is made up of beta-glucose molecules joined together by only 1,4-glycosidic bonds.
- starch is branched and has a coiling structure, however cellulose is unbranched and has a straight-chained structure.
- both cellulose and starch are insoluble and polysaccharides
