3.2 - Carbohydrates

An example of a monosaccharide is ________. a. fructose b. glucose c. galactose d. all of the above

D

Lactose is a disaccharide formed by the formation of a ________ bond between glucose and ________. a. glycosidic; lactose b. glycosidic; galactose c. hydrogen; sucrose d. hydrogen; fructose

B

Plant cell walls contain which of the following in abundance? a. starch b. cellulose c. glycogen d. lactose

B

Describe the similarities and differences between glycogen and starch.

Glycogen and starch are polysaccharides. They are the storage form of glucose. Glycogen is stored in animals in the liver and in muscle cells, whereas starch is stored in the roots, seeds, and leaves of plants. Starch has two different forms, one unbranched (amylose) and one branched (amylopectin), whereas glycogen is a single type of a highly branched molecule.

Cellulose and starch are examples of: a. monosaccharides b. disaccharides c. lipids d. polysaccharides

D

Why is it impossible for humans to digest food that contains cellulose?

The β 1-4 glycosidic linkage in cellulose cannot be broken down by human digestive enzymes. Herbivores such as cows, koalas, and buffalos are able to digest grass that is rich in cellulose and use it as a food source because bacteria and protists in their digestive systems, especially in the rumen, secrete the enzyme cellulase. Cellulases can break down cellulose into glucose monomers that can be used as an energy source by the animal.