Question 1

Which of the following sugars is NOT a homodisaccharide?

Accepted Answer

Lactose is not a homodisaccharide because it is composed of two different monosaccharide units, glucose and galactose, whereas homodisaccharides are composed of two identical monosaccharide units. Maltose, isomaltose, and cellobiose are all homodisaccharides, each composed of two glucose units.

Question 2

Cellulose is extremely resistant to hydrolysis,but cellulase can catalyze its hydrolysis.Which of the following is the source of cellulase?

Accepted Answer

Cellulase is primarily produced by bacteria that live in the rumen, which is a specialized stomach compartment found in ruminant animals such as cows and sheep. These bacteria are able to break down cellulose and extract nutrients from plant material, which is a key part of the digestive process for these animals. While other organisms such as fungi and some insects are also capable of producing cellulase, bacteria are the primary source in the rumen.

Question 3

Which of the following terms classifies the enzyme cellulase?

Accepted Answer

Cellulase is an enzyme that breaks down cellulose, a polymer of glucose linked by beta(1→4) glycosidic bonds. Therefore, cellulase must be a beta(1→4)glucosidase, and the correct option is B. Alpha(1→4)glucosidase and alpha(1→6)glucosidase break down alpha-linked glucose polymers, while beta(1→6)glucosidase breaks down a different type of beta-linked glucose polymer.

Question 4

Which of the following substances is a mucopolysaccharide that forms protective coats on animal cells?

Accepted Answer

Hyaluronic acid is a mucopolysaccharide that forms a protective coat on animal cells. Chitin is a structural polysaccharide found in the exoskeleton of arthropods and in the cell walls of fungi. Glycogen is a storage polysaccharide found in animals while glucuronic acid is a sugar acid derived from glucose.

Question 5

Which of the following dissaccharides represents trehalose,blood sugar in hemolymph of insects?

Accepted Answer

Trehalose is a disaccharide composed of two glucose units linked by an α,α-1,1-glycosidic bond, which is correctly represented by GlcααGlc.

Question 6

Which of the following is correct regarding the nature of glycogen?

Accepted Answer

Glycogen is a highly branched polymer of linked glucose residues, used for energy storage in animals. It is not a trisaccharide and does not have all non-reducing ends. It is primarily found in liver and skeletal muscles, not in the brain.

Question 7

Which of the following is a feature of dextrans?

Accepted Answer

The answer of Which of the following is a feature...

Question 8

Osmotic pressure is greatly reduced by formation of polysaccharide molecules from monosaccharide molecules.Which of the following does osmotic pressure depend on to accomplish this?

Accepted Answer

Osmotic pressure depends on the number of particles (molecules or ions) in solution. When monosaccharides combine to form polysaccharides, the number of molecules decreases, thus reducing the osmotic pressure.

Question 9

Which of the following compounds is typical of the oligosaccharide components found in beans,etc.,that are not digested in the stomach,but are digested by bacteria in the intestines,causing flatulence?

Accepted Answer

Stachyose is a common oligosaccharide found in beans, peas, and other legumes that humans cannot digest but are broken down by bacteria in the large intestine, causing gas and bloating. Dextrantriose and melezitose are not typically found in beans and are not known for causing flatulence. Maltose is a disaccharide commonly found in grains and is digested by humans without involvement of intestinal bacteria.

Question 10

Which of the following carbons of glucose is oxidized upon formation of glucuronic acid?

Accepted Answer

Glucuronic acid is formed by the oxidation of the sixth carbon of glucose.

Question 11

Which of the following enzymes is found in liver and muscle tissue and is used to catalyze the hydrolysis of glycogen to glucose-1-phosphate?

Accepted Answer

Glycogen phosphorylase is the enzyme found in liver and muscle tissue that catalyzes the hydrolysis of glycogen to glucose-1-phosphate. Beta (1→6)-glucosidase is involved in the breakdown of cellulose, alpha-amylase breaks down starch, and glycogen maltase breaks down glycogen during the final stages of glycolysis.

Question 12

Which of the following sugars is commonly referred to as cellulose?

Accepted Answer

Cellulose is a linear polymer consisting of repeating units of (1→4)-β-D-glucopyranan, making B the correct choice. A is a type of mannose sugar, but not cellulose. C and D are both types of branched mannose and glucose sugars, respectively, but not cellulose.

Question 13

Which of the following characteristics is common to both cellulose and a-amylose?

Accepted Answer

The answer of Which of the following characteristics is common...

Question 14

Which of the following statements explains why cooked starch is more digestible than uncooked starch?

Accepted Answer

Cooking causes the starch granules to take up water, swell, and become more accessible to the enzymes that hydrolyze the starch. This makes the starch more digestible.

Question 15

In plant cells,starch is hydrolyzed by starch phosphorylase.Which of the following is released upon hydrolysis?

Accepted Answer

Starch phosphorylase hydrolyzes starch by cleaving off glucose molecules one at a time from the non-reducing ends of the polymer. This reaction yields glucose-1-phosphate and a smaller starch molecule with one less glucose unit. Therefore, option A is the best choice as it correctly describes the products of the hydrolysis reaction.

Question 16

Neither α-amylase nor β-amylase can cleave the α(1→6)glycosidic bonds of amylopectin.Which of the following enzymes is required to completely hydrolyze starch?

Accepted Answer

α-amylase and β-amylase can only cleave α(1→4) glycosidic bonds in starch, which generates maltose and other small oligosaccharides. However, the α(1→6) glycosidic bonds in amylopectin require the action of an additional enzyme, α(1→6)-glucosidase, to completely break down the starch into glucose. Glycogen phosphorylase and maltase are not involved in the breakdown of starch, and sucrase specifically cleaves sucrose, not starch. Therefore, A) α(1→6)-glucosidase is the best choice to completely hydrolyze starch.

Question 17

Which of the following disaccharides is NOT a reducing sugar?

Accepted Answer

Sucrose is not a reducing sugar because it does not have a free anomeric carbon that can participate in a reducing reaction. Lactose and maltose are reducing sugars because they have a free anomeric carbon on the glucose monomers. Cellulose is not a sugar, it is a polysaccharide made up of repeating glucose units linked together by β 1-4 glycosidic bonds.

Question 18

Which of the following statements explains why the disaccharide sucrose is a reducing sugar?

Accepted Answer

The answer of Which of the following statements explains why...

Question 19

Which of the following does NOT apply to both cellulose and chitin?

Accepted Answer

Cellulose is a polymer of glucose, whereas chitin is a polymer of N-acetylglucosamine, not glucose.

Question 20

Which of the following is a characteristicof cellulose fibre?

Accepted Answer

Intermolecular hydrogen bonds are a major contributor to the stability of cellulose microfibrils. Choice A is incorrect because cellulose is composed of linear chains of β(1→4)glycosidic-linked glucose residues only. Choice B is incorrect because cellulose is not easily hydrolyzed. Choice C is incorrect because cellulose microfibrils are actually very strong.

Quiz 7: Carbohydrates and the Glycoconjugates of Cell Surfaces