1.4- STARCH, GLYCOGEN AND CELLULOSE Flashcards
What is starch?
a polysaccharide found in many parts of a plant in the form of small grains
Where do especially large amounts of starch occur?
in seeds and storage organs, such as potato tubers
Why is starch an important component of food?
major energy source in most diets
What is starch made up of?
chains of α-glucose monosaccharides linked by glycosidic bonds
How are glycosidic bonds formed?
by condensation reactions
How can the chains of starch be?
branched or unbranched
What happens to the unbranched chains of starch?
wound into a tight coil that makes the molecule very compact
What is the main role of starch?
energy storage
How is starch being insoluble helpful?
doesn’t affect water potential, so water is not drawn into the cells by osmosis
How is starch being large and insoluble helpful?
does not diffuse out of cells
How is starch being compact helpful?
so a lot of it can be stored in a small space
How is when starch is hyrdrolysed it forms α-glucose helpful?
easily transported and readily used in respiration
How does the starch with branched forms having many ends helpful?
the ends can be acted on by enzymes simultaneously meaning that glucose monomers are released very rapidly
Where is starch never found?
in animal cells
What similar polysaccharide similar to starch serves the same role?
glycogen
Where can glycogen be found?
in animals and bacteria but never in plant cells
Glycogen is very similar to the structure of what?
the structure of starch but glycogen has shorter chains and is more highly branched
Why is glycogen sometimes called “animal starch”?
as it is the major carbohydrate storage product of animals
How is glycogen stored in animals?
as small granules mainly in the muscles and the liver
Why is the mass of carbohydrates that is stored relatively small?
as fat is the main storage molecule in animals
How is glycogen being insoluble helpful?
does not tend to draw water into the cells by osmosis
does not diffuse out of cells
How is glycogen being compact helpful?
so a lot of it can be stored in a small space
How is glycogen being more highly branched than starch and having more ends make is helpful?
it can be acted on simultaneously by enzymes. Therefore more can be rapidly broken down to form glucose monomers, which are used in respiration
Why is glycogen being broken down into glucose important?
it’s important to animals which have a higher metabolic rate and therefore respiratory rate than plants because they are more active
