Energy storage molecule properties
- compact, energy dense
- insoluble so wouldn’t effect water potential
- Easy to add glucose to (condensation)
- easy to remove glucose (hydrolysis)
- metabolically inactive so will not participate in any reactions
where is starch found and what is its function
found in plants, is an energy storage molecule
What is starch made up of
Repeating units of glucose
2 Types of starch molecules
amylose , amylopectin
Main difference between amylose and amylopectin
Form different glycosidic bonds
amylose structure and where found
- found in plants, stored as starch grains
- makes up 30% of starch
- A long un-branched chain of alpha glucose molecules
- Connected by 1-4 glycosidic bonds
- chain coils up on itself into a spiral shape, compact helix, held together by hydrogen bonds
- OH group is arranged on the inside of the coil, meaning its less soluble.
Amylopectin structure and where found
- makes up 70% of starch , stored as starch grains
- found in plants
- chains of glucose connected by 1-4 glycosidic bonds, forming a helical shape
- Around every 25 glucose units, a 1-6 glycosidic bond is formed by condensation, creating a branch
- highly branched structure means multiple sites fro hydrolysis, allowing glucose to be removed quickly.
- this makes it denser in energy availability
Glycogen structure and where its found and function
- Found in animals and fungi
- stored in the muscle and liver cells.
- an energy storage molecule
- made up of glucose
- Branched around every 10th molecule with a 1-6 glycosidic bond.
Key properties of amylopectin and glycogen
insoluble, branched and compact
extensive branching is a benefit because
more free ends are available for hydrolysis and condensation reactions.
Compaction is a benefit because
so that many glucose units as possible can be stored for future use
cellulose structure
- long, unbranched chains of β glucose
- Alternate beta glucose molecules flip forwards 180
- Form a 1-4 glycosidic bond
- No branches or coils, a straight chain bond
Why do cellulose chains not coil into the helical shape?
- due to bonding
- hydrogen bonds stop it from spiralling
- hydrogen bonds form in between the chains
what are microfibrils
Hydrogen bonds that have formed between the chains create microfibrils - many chains bonded together
what are macrofibrilis
many microfibrils joined together
What are fibres
Many macrofibrils joined together
They have high tensile strength
insoluble
pectin supports the cellulose fibres
functions of cellulose
- cell wall, provides high tensile strength
- prevents cell bursting when turgid
- fully permeable, due to space between macrofibers
- insoluble
- inert
Why is cellulose important to humans
Hard to break down, forms fibre which is necessary for a healthy digestive system
