1.4 — carbohydrate: polysaccharide Flashcards
what are 4 examples of polysaccharides?
starch (unbranded), starch (branched), glycogen, cellulose
how is starch used?
by plants to store excess glucose — being hydrolysed back into glucose when plants require energy
what is starch made up of?
many alpha glucose monomers joined by both 1,4 and 1,6 glycosidic bonds to form chains
what are the two forms of starch chain?
unbranched and branched
what features of starch allow it to work well as a store of energy? (5)
- insoluble — does not affect water potential of the cell, so water is not drawn to it by osmosis
- large — cannot diffuse out of cells
- many side branches — allows enzymes to hydrolyse the glycosidic bonds easily to rapidly release glucose
- coiled — makes it compact do that a lot of glucose can be stored in a small space
- hydrolysis releases alpha glucose monomers — these are readily used in respiration
what is glycogen used for and by whom?
glycogen is used by animals to store excess glucose
what is glycogen made up of?
glycogen is made up of many alpha glucose monomers which are joined via both 1,4 and 1,6 glycosidic bonds
what features of glycogen allow it to work well as a store of energy? (5)
- insoluble — it does not affect the water potential of cells, and therefore does not cause water to enter cells via osmosis
- compact — a lot of glucose can be stored in a small place
- more highly branched than starch — enzymes can easily hydrolyse the glycosidic bonds to rapidly release glucose
- large — cannot diffuse out of cells
- releases alpha glucose molecules — (via hydrolysis) they can be used in respiration
what is cellulose made from?
cellulose is a polysaccharide formed from beta glucose.
what is cellulose’s primary use?
to provide structural support for plant cell walls
what must beta glucose monomers do to be able to bond to each other and why?
one monomer must invert 180˚(flip upside down) as when unflipped beta glucose line up next to each other, the hydroxyl groups (OH) on carbons 1 and 4 are too far to form a 1,4 glycosidic bonds. by one beta glucose being flipped, the hydroxyl groups are close enough to react
what type of chains do beta glucose monomers form? (3)
long, straight, unbranched chains
what does the alternating inversion of the beta glucose molecules allow?
it hydrogen bonds to form between individual chains, which in huge numbers provides strength to cellulose.
what do multiple cellulose chains linked via hydrogen bonds form (2)?
bundles called microfibrils which join together to make macrofibrils, which then combine to make strong cellulose fibres in the plant cell wall.
how has cellulose adapted to its role? (3)
- long, straight and unbranched chains — provide rigidity to the cell wall
- hydrogen bonds — these cross link the chains to add collective tensile strength
- microfibrils - these provide additional strength
