$$ \text{D-Glucose} + O_2$ \xrightarrow{\text{Glucose oxidase}} \text{D-Gluconic acid} + H_2O_2 $$

Question 1

Which of the following statements best explains why D-glucose is classified as a reducing sugar?

Accepted Answer

It contains an aldehyde group in its open-chain form that can be oxidized to a carboxylic acid.

Question 2

A clinical test for glucose in urine uses glucose oxidase and peroxidase. What is the chemical reaction catalyzed by glucose oxidase?

Accepted Answer

$$ 	ext{D-Glucose} + O_2$ \xrightarrow{	ext{Glucose oxidase}} 	ext{D-Gluconic acid} + H_2O_2 $$

Question 3

Which of the following is the product of the reduction of D-mannose?

Accepted Answer

D-mannitol

Question 4

In the reaction of D-glucose with Benedict’s solution, what is the color change observed and what does it indicate?

Accepted Answer

Blue to brick red, indicating the presence of a reducing sugar.

Question 5

Fructose is a ketohexose and cannot be oxidized directly. How does it react with Benedict’s solution?

Accepted Answer

It rearranges to form glucose, which can then be oxidized.

Question 6

Which of the following disaccharides is NOT a reducing sugar?

Accepted Answer

Sucrose

Question 7

What type of glycosidic bond is found in maltose?

Accepted Answer

$$ \alpha-1,4 $$ glycosidic bond

Question 8

Which monosaccharides make up lactose?

Accepted Answer

$$ \beta -D-$$galactose and $$ \alpha -D-$$glucose

Question 9

Which statement about sucrose is correct?

Accepted Answer

Sucrose contains an $$ \alpha \beta -1$$,2-glycosidic bond between glucose and fructose.

Question 10

Which sugar alcohol is commonly used as a sweetener in sugar-free gum and is produced from the reduction of D-glucose?

Accepted Answer

D-sorbitol

Question 11

Amylose is a polysaccharide found in starch. Which type of glycosidic bond connects its glucose units?

Accepted Answer

$$ \alpha -1$$,4-glycosidic bonds

Question 12

Which structural feature distinguishes amylopectin from amylose?

Accepted Answer

Amylopectin contains both $$ \alpha -1$$,4 and $$ \alpha -1$$,6-glycosidic bonds, while amylose contains only $$ \alpha -1$$,4-glycosidic bonds.

Question 13

Cellulose is a major structural unit in plants. Why can humans not digest cellulose?

Accepted Answer

Humans lack the enzyme to hydrolyze $$ \beta -1$$,4-glycosidic bonds.

Question 14

Which polysaccharide is stored in the liver and muscle of animals and is highly branched?

Accepted Answer

Glycogen

Question 15

A patient’s urine is tested with a glucose oxidase strip. The strip turns green-brown. What is the approximate glucose concentration in the urine?

Accepted Answer

500 mg/dL

Question 16

Which artificial sweetener is made by replacing hydroxyl groups in sucrose with chlorine atoms?

Accepted Answer

Sucralose

Question 17

Aspartame is a noncarbohydrate sweetener. Which two components make up its structure?

Accepted Answer

Aspartate and a methyl ester of phenylalanine

Question 18

Which of the following best describes the glycosidic bond in cellulose?

Accepted Answer

$$ \beta -1$$,4-glycosidic bond

Question 19

Which sugar has the highest relative sweetness compared to sucrose?

Accepted Answer

Fructose

Carbohydrates: Structure, Properties, and Biological Significance

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