Chapter 5: What Do Carbohydrates Do?

Question 1

What are the three functions of carbohydrates in cells?

Answer 1

1. Provide fibrous structural materials
   
   2. Mark cell identity
   3. Store chemical energy

Question 2

_____ and _____, along with the modified polysaccharide ______, are key structural compounds. They form fibers that give cells and organisms _____ and elasticity.

Answer 2

Cellulose, chitin, peptidoglycan, strength

Question 3

Only a few organisms have enzymes capable of digesting cellulose, chitin, or peptidoglycan. These fibers tend to be _____ thanks to the strong interactions between strands consisting of ____-1,_-glycosidic linkages. The exclusion of water within these fibers makes them more difficult to hydrolyze, so they are resistant to degradation and decay.

Answer 3

insoluble, beta, 4

Question 4

The _____ that you ingest when you eat plants—what biologists call _____ _____—forms a porous mass that absorbs and retains water. This sponge-like mass adds moisture and bulk that helps fecal material move through the intestinal tract more quickly, preventing constipation and other problems.

Answer 4

cellulose, dietary fiber

Question 5

What is glycosylation?

Answer 5

the covalent modification of other molecules with one or more carbohydrates

Question 6

A _____ is a lipid that has been glycosylated, meaning it has one or more _____ attached _____. A _____ is a protein that is similarly linked to carbohydrates.

Answer 6

glycolipid, covalently, carbohydrates, glycoprotein

Question 7

Glycosylation _____ differ among different _____ types. These differing patterns enable ___-___ recognition and/or signaling.

Answer 7

patterns, cell, cell-cell

Question 8

In cells today, the energy in _____ is transformed into _____ energy, and the energy is stored in _____. For example, plants harvest the energy in sunlight and store it in the bonds of _____ by the process known as _____.

Answer 8

light, chemical, sugars, carbohydrates, photosynthesis

Question 9

Starch and glycogen are efficient energy-storage molecules because they polymerize via ____-glycosidic linkages instead of the ____-glycosidic linkages in the structural polysaccharides. The α-linkages in storage polysaccharides are readily _____ to release glucose, while the structural polysaccharides resist enzymatic _____.

Answer 9

alpha, beta, hydrolyzed, degradation

Question 10

The most important enzyme involved in catalyzing the hydrolysis of α-glycosidic linkages in glycogen molecules is a protein called _____.

Answer 10

phosphorylase

Question 11

The enzymes involved in breaking the ____-glycosidic linkages in starch are called _____. Your salivary glands and pancreas produce _____ that are secreted into your mouth and small intestine, respectively.

Answer 11

alpha, amylases, amylases

Question 12

The glucose subunits that are _____ from _____ and _____ are processed in reactions that result in the production of _____ energy that can be used in the cell

Answer 12

hydrolyzed, glycogen, starch, chemical