polysaccharides Flashcards
what are polysaccharides?
carbohydrates
what is the bond called between monosaccharides?
glycosidic
how are polysaccharides broken down? what are they broken down into?
hydrolysis, monosaccharides
what is amylose broken down into?
alpha glucose molecules
how are polysaccharides formed?
through the condensation of many glucose units
how do cells get energy?
from glucose
how do plants store excess glucose?
store it as starch which is broken down into glucose when needed
what is starch?
a polysaccharide found in plants
what is starch made from?
long chains of alpha glucose
how can starch be stored in small spaces?
it coils very tightly so is compact
is starch soluble? what does this mean for the cell?
no, its insoluble so it doesn’t affect the osmotic balance/water potential of the cell
why can’t starch leave the cell?
because its a long molecule made of many glucose units, its too big
what is amylose? what is its structure?
an unbranched version of starch that only consists of alpha 1,4 links. The angles of the glycosidic bonds give it a coiled structure. A lot can fit into a small space and it is compact.
what is amylopectin? what is its structure?
A branched form of starch which consists of alpha glucose 1,4 links with branches formed by 1,6 links. The side chains allow the enzymes that break down the molecule to get to the bonds easily. The are a good source of quick glucose.
what is the test for starch?
Add iodine in potassium iodide solution and if sample goes from brown/orange to blue/black starch is present.
what is glycogen and where is it found?
a polysaccharide found in animals as small granules mainly found in muscles and the liver
what is glycogen useful for?
useful as an energy storage molecule as its easily hydrolysed back to glucose and is compact. Lots of branches means that stored glucose can be released quickly
describe the structure of glycogen
formed from short chains of alpha glucose and is branched
what is cellulose made from?
long unbranched chains of beta glucose
what happens when a glycosidic bond forms in cellulose?
the molecule rotates 180º to the next to form a zig zag. The OH on carbon 1 is inverted
describe the structure of cellulose
the beta chains line up and hydrogen bonds form crosslinks. The hydrogen bonds by themselves are quite weak but together they are strong
what do cellulose chains form? what do they do?
microfibrils which lie parallel to form fibres. They are strong fibres which provide structural support
what is cellulose used for?
used in cell walls to provide rigidity. It applies inward pressure to withstand the pressure to stop the cell from bursting. This is when the plant is turgid.
Is starch soluble or insoluble? Why is this a benefit?
It is insoluble in water so doesn’t affect water potential. Therefore, it doesn’t cause water to enter the cell by osmosis which would make them swell
