20. Carbohydrates

Which plant-based polysaccharide possesses only a-1,4 glycosidic linkages?

Hydrolysis of both glycosidic bonds in the following trisaccharide A, B, C yields three monosaccharides. 

c. Draw the Fischer projections for the three monosaccharides.

Are one or more of the disaccharides maltose, lactose, cellobiose, and sucrose part of the trisaccharide in Problem 20.23? If so, identify which disaccharide and its location. (Hint: Look for an α-1,4 link, ß-1,4 link, or 1,2 link, and then determine if the correct monosaccharides are present.)

Amylose (a form of starch) and cellulose are both polymers of glucose. What is the main structural difference between them? What roles do these two polymers have in nature?

How are amylose and amylopectin similar to each other, and how are they different from each other?

Give the name of one or more polysaccharides that matches each of the following descriptions:

c. contains only α(1→4)-glycosidic bonds

Give the name of one or more polysaccharides that matches each of the following descriptions:

b. contains only ß(1→4)-glycosidic bonds

Give the name of one or more polysaccharides that matches each of the following descriptions:

d. produces maltose during digestion

Melezitose, a carbohydrate secreted by insects, has the following Haworth structure: (13.4, 13.5, 13.6) <IMAGE>

a. Is melezitose a mono-, di-, or trisaccharide?

Melezitose, a carbohydrate secreted by insects, has the following Haworth structure: (13.4, 13.5, 13.6) <IMAGE>

b. What monosaccharides are present in melezitose?

Melezitose, a carbohydrate secreted by insects, has the following Haworth structure: (13.4, 13.5, 13.6) <IMAGE>

c. Is raffinose a reducing sugar?

Give the name of one or more polysaccharides that matches each of the following descriptions:

a. not digestible by humans

Describe the similarities and differences in the following:

a. amylose and amylopectin

Describe the similarities and differences in the following:

a. amylose and cellulose

Give the name of one or more polysaccharides that matches each of the following descriptions:

b. the storage form of carbohydrates in plants

What are the disaccharides and polysaccharides present in each of the following?

a. <IMAGE>

ALLIED Health Our bodies cannot digest cellulose because we lack the enzyme cellulase. Why is cellulose an important part of a healthy diet if we cannot digest it?

Describe the properties of soluble fiber.

ALLIED Health Based on the sweetness index in Table 6.2, if you tasted a drop of each of the syrups below, which would taste the sweetest?

(a) light corn syrup (100% glucose)

ALLIED Health If one sweetener packet of Splenda, Sweet’N Low, or Equal has the same sweetness as two tablespoons of sugar, according to Table 6.2, which of the packets contains the smallest amount of the sweetener?

Describe the similarities and differences of the following polysaccharides:

(a) amylose and amylopectin

Give the name of one or more polysaccharides that matches each of the following descriptions:

(a) not digestible by humans

ALLIED Health How is the polysaccharide heparin different from the glucose polysaccharides?

Give the name of one or more polysaccharides that matches each of the following descriptions:

(d) produces maltose during digestion

The shell of a shrimp is composed of chitin. If you eat a boiled shrimp without removing the shell, will your body break the shell down into its component sugars? Explain. (Hint: Compare chitin’s structure to that of amylose and cellulose.)

Glycogen and amylopectin are both branched polymers of glucose. Read the descriptions of each in Section 6.6. Which molecule has a more compact structure? Explain.

ALLIED Health Which of the components in starch is more likely to be broken down more quickly in plants, amylose or amylopectin? Why?

How much energy is produced if a person eats 50 g of digestible carbohydrate (not fiber) in a day? In this case, what percent of a 2200 Calorie diet would be digestible carbohydrate? Recall that carbohydrates provide four Calories of energy per gram consumed.