3. Polysaccharides - Function of polysaccharides Flashcards
Name 3 polysaccharides?
Starch.
Glycogen/
Cellulose.
Where do cells get their energy from?
Glucose/
What do plants store excess glucose as?
Starch.
When a plant needs more glucose for energy, it breaks down starch to release the glucose.
What is starch?
A mixture of 2 polysaccharrides of alpha glucose.
Amylose and amylopectin.
How can you test the presence of starch?
Using iodine.
Orange brown colour to dark blue blac
What is amylose?
A long, unbranched chain of alpha glucose.
What is the structure of amylose like?
The angles of the glycosidic bond give it a coiled structure, almost like a cylinder.
This makes it compact, really good for storage as you can fit more into a small space.
What is amylopectin?
Long, branched chain of alpha glucose.
How does the structure of amylopectin help with its function?
As the side branches allow the enzymes to get at the glycosidic bonds easily.
Meaning glucose can be released quickly.
What helps to hold AMYLOSE’ helical structure?
Hydrogen bonds between the alpha glucose molecules.
What is starch like in water?
It is insoluble in water and doesn’t affect water potential.
Doesn’t cause water to enter cells by osmosis, making them swell.
Meaning its good for storage.
Name a reason why starch is good storage molecule?
Its too large to it can’t leave the cell.
Where do animal cells get their energy from?
Glucose.
What do animals store excess glucose as?
Glycogen.
What is the structure of glycogen?
Has lots of side branches coming off it.
Stored glucose can be released quickly, this is important for energy release in animals.
Compact molecule, good for storage.
What is cellulose made of?
Long, unbranched chains of beta glucose.
When beta glucose molecules bond they from straight cellulose chains.
What is the structure of cellulose like?
The cellulose chains are linked together by hydrogen bonds to from strong fibres called microfibrils.
Strong fibres = cellulose provides structural support for cells.
What is the function of glycogen?
Acts as an energy store or reserve.
Storage of starch
Medium storage
Meaning when the plants need to the starch can be broken down into alpha glucose
How is starch formed v
Many condensation reactions of alpha glucose
Why is starch useful ?
Insoluble meaning it doesn’t affect water potential / doesn’t diffuse out of cell
Compact - stores loads
Hydrolysis of starch into alpha glucose means it’s easy for transport and used for respiration
Glycogen storage
Medium term storage
So animal can break down glycogen into alpha glucose when it needs to
What molecule is glycogen also similar to ?
Starch
Both have side branches
Glycogen however has shorter chains and more branches
What does it mean that glycogen has more shorter branches ?
More readily hydrolyised
How is cellulose different to starch and glycogen ?
It’s used for structural purposes not storage (energy)
formed by hydrolysis of beta glucose not alpha
It’s unbranched hydrogen bonds forms cross links called microfibrils
In order to form a straight cellulose chain, what must happen ?
Each monomer must rotate 180 degrees
How is cellulose strong ?
Cross link chains and many hydrogen bonds
