Chapter 3 Carbohydrates

Question 1

Major Polysaccharides

Answer 1

glycogen, starch, cellulose (all repeating units of glucose)

Question 2

Disaccharides

Answer 2

Two sugars; sucrose the most significant

Question 3

Which polysaccharide is the most important nutritionally?

Answer 3

Sucrose; 1 glucose, 1 fructose; furnishes 1/3 of total dietary carbohydrate in an average diet.

Question 4

D. vs L.

Answer 4

D (OH group on right); L (OH group on left) @ highest numbered chiral carbon: Enzymes specifically work for the D form of carbohydrates

Question 5

In Solution, what form do monosaccharides exist in?

Answer 5

not in an open-chair form; they exist in a cyclic ring structure.

Question 6

alpha v. beta conformations

Answer 6

a if OH to the right in fisher projections; if faces right, OH group faces down; a/b go to equilibrium w/ b form roughly twice that of a form.

Question 7

HFCS

Answer 7

55% fructose and 45% glucose

Question 8

glycosidic bond

Answer 8

OH group of one monosaccharide joins OH of another through the elimination of H2O

Question 9

Most Common Disaccharides

Answer 9

maltose, lactose, and sucrose

Question 10

Lactose

Answer 10

galactose linked by B 1,4 glycosidic bond to glucose

Question 11

maltose

Answer 11

Two glucose molecules joined by a (1,4) bond

Question 12

Sucrose

Answer 12

most abundant sweetener, non-reducing, glycosidic bond includes anomeric hydroxyl of both residues.

Question 13

What is the most common digestible polysaccharide in plants?

Answer 13

Starch; two forms (amylose and amylopectin)

Question 14

Amylose

Answer 14

type of starch; linear a (1,4) bonds contributes to 15-20% of starch

Question 15

Amylopectin

Answer 15

type of starch; branched w/branching points having a (1,6) bonds contributes to 80-85% of starch

Question 16

Glycogen

Answer 16

The main storage form of carbohydrate in animal tissues, Localized primarily in the liver and muscle tissues.

Question 17

Cellulose

Answer 17

b (1,4) bonds. repeating units of glucose, undigestible

Question 18

Salivary Amylase

Answer 18

Active in the Saliva/inactive in the stomach. hydrolyzes a (1,4) linkages

Question 19

Pancreatic a-amylase

Answer 19

hydrolyzes a (1,4) linkages in amylose and amylopectin produces dextrins.

Question 20

a-dextrinase

Answer 20

also called sucrase-isomaltase, acts on limit dextrins (can work on a(1,6) linkages. has two active sites. 1) a(1-4) linkages/Sucrase 2) a(1-4) and a(1-6)/isomaltase attached to brush border membrane. Only intestinal enzyme that hydrolyzes a(1-6) glycosidic bonds.

Question 21

Digestion of Disaccharides

Answer 21

Only occurs in the upper intestine via disaccharidase activity at the brush border. a

Question 22

Lactase

Answer 22

digests lactose to galactose and glucose; hydrolyzes b(1-4) linkages.

Question 23

Trehalase

Answer 23

enzyme that hydrolyzes trehalose a(1-1) bond into glucose and glucose.