A-Level Biology OCR A
Bonds Glucose Energy Glycosidic Alpha Bonding Side Hydrogen
Starch is insoluble, preventing osmotic issues. Its helical (amylose) or branched (amylopectin) structure allows for compact energy storage and quick hydrolysis due to accessible branch points.
El almidón es insoluble, lo que evita cambios en el potencial hídrico y la ósmosis. Su estructura helicoidal (amilosa) o ramificada (amilopectina) permite un almacenamiento de energía compacto y de fácil acceso para la hidrólisis.
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Relate structural properties to the functions of starch wrt solubility, size, bonding and presence of side chains. |
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Solubility & Size- Insoluble - does not affect water potential & does not cause osmotic swell
- Too large of a molecule, overcomes water's hydrogen bonds attempting to separate the molecules (amylose - 300 glucose molecules, amylopectin - 3000 glucose molecules)
- Makes it good for storage - stays inside the plant cells without dissolving into the system
- Many glucose units stored in one molecule - more energy dense than storing them separately
Bonding & Side chains - Amylose - only alpha 1,4 glycosidic bonds which have a bond angle that makes it form a helical structure further stabilised by intramolecular hydrogen bonds (between -OH groups between neighboring monomers) meaning it is more compact than if a straight chain - energy dense
- Amylopectin - alpha 1,4 glycosidic bonds, every ~20C - alpha 1,6 glycosidic bond which forms a branched structure of helical chains - even more energy stored
- 1,6 glycosidic bonds allow for more branch endings for enzyme activity - easy to hydrolyse and release the glucose for energy quickly
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A-Level Biology OCR A