Polysaccharides Flashcards
What are the features of energy storage molecules
They are compact - energy dense
They are insoluble - so they don’t affect the water potential for the cell
Easy to add glucose to - condensation reaction
Easy to remove glucose from - hydrolysis
Metabolically inactive
Where is starch found
Starch is found in chloroplasts and in membrane bound starch grains
Where is glycogen found
Glycogen is found in the liver
What are starch and glycogen
Two polysaccharides made from glucose
What is amylose
Amylose is a polysaccharide that contains glucose molecules joined mainly by 1-4 glycosidic bonds
What is the structure of amylose and why
a 1-4 glycosidic bonds resulting in unbranched chains forming a compact helical structure
What is the structure of amylopectin
Amylopectin also contains glucose molecules joined by a 1-4 glycosidic bond but it also has a 1-6 glycosidic bond resulting in amylopectin having a highly branched structure.
What percentage of starch is made up by amylose
30% of starch
What is amylose held together by
Its spiral shape is held in place by hydrogen bonds.
Where are the OH groups in amylose
They are inside the coil making amylose less soluble as these are the groups that would hydrogen bond with water.
What percentage of starch is amylopectin
70%
what is the structure of amylopectin in starch
It coils into a spiral shape, and is held together with hydrogen bonds, but with branches emerging from the spiral.
Why is the structure of amylopectin good for a storage molecule
it provides multiple sites for hydrolysis allowing glucose to be removed quickly
What is glycogen made from
It is made of glucose
how is glycogen stored
it is stored as small granules particularly in the muscles and liver
What are the branch points in glycogen from
they are from the 1-6 glycosidic bond
what is the comparison between glycogen and starch
It is more coiled and compact than amylopectin. Indicating a higher metabolic rate of animals compared to plants.
What is cellulose used for
It is the main component of plant cell walls
What are the properties of cellulose
They are insoluble, have a high tensile strength, unreactive and flexible
What is the structure of cellulose
The glucose molecules are linked together by a beta 1-4 glycosidic bond. However, every other glucose molecule rotates 180 degrees so that the hydroxyl groups on each molecule are adjacent to each other.
What does this bonding mean for cellulose
It results in long unbranched chains, the hydrogen bonding between chains gives cellulose molecules great tensile strength which is ideal for supporting plant cells.
What do 60-70 cellulose chains do together
They bind together to form microfibrils
What do 400 microfibrils do
They bundle together to form macrofibrils
How do macrofibrils increase their tensile strength
They join in all directions criss-crossing the wall for extra tensile strength.
