Chapter 5: Carbohydrates - Homework Questions

What are the consequences? 1. α-1,4-glycosidic linkages more resist to degradation. 2. α-1,4-glycosidic linkages are much more likely to form linear fibers and sheets. 3. β-1,4-glycosidic linkages more resist to degradation. 4. β-1,4-glycosidic linkages are much more likely to form linear fibers and sheets.

3 and 4 only

Which polysaccharide contains a modified monosaccharide? a.) Starch b.) Peptidoglycan c.) Glycogen d.) Cellulose

B; The N-acetylglucosamine and N-acetylmuramic acid units that make up peptidoglycan are composed of modified glucose monomers.

Which of the following complex carbohydrates is listed with its correct function? a.) Chitin: constituent of bacterial cell walls b.) Amylose: main component of plant starch c.) Cellulose: structural component of plant cell walls d.) Starch: primary energy-storage molecule in animals

C

True or false? Peptidoglycan is a polysaccharide found only in bacteria.

True

Chapter 5: Carbohydrates - Homework Questions

Chapter 5: Carbohydrates - Homework Questions

Is the sugar in your soda affecting your mind? A 20-ounce soda typically contains 15 teaspoons of either sucrose or high-fructose corn syrup. These sugary beverages are a leading source of calories in the American diet and have been correlated with obesity and diabetes. There may be even more to this sweet dilemma, however. Could the sugars found in soda be altering your brain function?

Continue ------->

If you hold a salty cracker in your mouth long enough, it will begin to taste sweet. What is responsible for this change in taste? a.) Lysozyme breaks down the cellulose in the cracker into glucose monomers, which stimulate the sweet receptors in your tongue. b.) Amylase breaks down the glycogen in the cracker into glucose monomers, which stimulate the sweet receptors in your tongue. c.) Lysozyme breaks down the starch in the cracker into glucose monomers, which stimulate the sweet receptors in your tongue. d.) Amylase breaks down the starch in the cracker into glucose monomers, which stimulate the sweet receptors in your tongue.

D

Lysozyme, an enzyme found in human saliva, tears, and other secretions, catalyzes the hydrolysis of the β-1,4-glycosidic linkages in peptidoglycan. Predict the effect of this enzyme on bacteria. a.) Lysozyme destroys the nucleoid, preventing the reproduction of the bacteria. b.) Lysozyme destroys bacterial flagella, leading to the immobilization of the bacteria. c.) Lysozyme has no effect on bacteria. d.) Lysozyme destroys bacterial cell walls, leading to the death of the bacteria.

D

Which of these is a polysaccharide? a.) sucrose b.) galactose c.) glucose d.) cellulose e.) lactose

D

Glycogen is _____. a.) a polysaccharide found in plant cell walls b.) the form in which plants store sugars c.) a source of saturated fat d.) a polysaccharide found in animals e.) a transport protein that carries oxygen

D; Animals store energy in the form of glycogen.

A sugar that has the chemical formula C5H10O5 would be characterized as a(n) _____. a.) hexose b.) triose c.) oligosaccharide d.) pentose

D; Pentose is the general term for a five carbon sugar such as ribose.

Polymers that contain sugars....... a) may store hereditary information. b) may store energy. c) may protect cells. d)Both (b) and (c). e) (a), (b), and (c).

E

The bond that joins two monosaccharides into a disaccharide is a(n) _____.

Glycosidic bond

What is the difference between linking glucose molecules with α-1,4-glycosidic linkages versus β-1,4-glycosidic linkages? 1. n α-1,4-glycosidic linkages the glucose monomers are linked in the same orientation. 2. In α-1,4-glycosidic linkages every other glucose flipped in orientation. 3. In β-1,4-glycosidic linkages every other glucose flipped in orientation. 4. The linkages are located on opposite sides of the plane of the glucose rings. 5. In β-1,4-glycosidic linkages the glucose monomers are linked in the same orientation. 6. The linkages have different orientation of the glucose monomers.

1, 3 ,4, 6

1. Lactose, the sugar in milk, is a ____________, because it can be split into two monosaccharides. 2. A carbohydrate that yields many monosaccharides when hydrolyzed is a ________________. 3. A simple sugar is composed of equal parts carbon and water, which gave rise to the general name of any sugar as a _________________. 4. A ___________ cannot be hydrolyzed any further.

1. Disaccharide 2. Polysaccharide 3. Carbohydrate 4. monosaccharide

Cellulose, chitin, and peptidoglycan function as structural molecules and withstand pulling and pushing forces well. Which structural feature is most directly responsible? a.) Structural polysaccharides exist as sets of long, parallel strands that are linked to one another. b.) Structural polysaccharides are built with β1, 4glycosidic linkages that are very strong. c.) Structural polysaccharides are built with β-1,4-glycosidic linkages, which are very resistant to hydrolysis. d.) Structural polysaccharides exist as highly branched helices.

A

Sucrose is cleaved in your saliva by the enzyme sucrase to release glucose and fructose. Use the structural formula of sucrose to describe fructose using the terms that define its carbon number and placement of the carbonyl group. a.) Fructose is a hexose based on having six carbons, and it is a ketose because the carbonyl is within the carbon chain (C-2). b.) Fructose is a pentose based on having five carbons, and it is a ketose because the carbonyl is within the carbon chain (C-2). c.) Fructose is a hexose based on having six carbons, and it is an aldose because it has the carbonyl group is at the end of the carbon chain (C-6). d.) Fructose is a pentose based on having five carbons, and it is an aldose because it has the carbonyl group at the end of the carbon chain (C-1).

A

What holds cellulose molecules together in bundles large enough to form fibers? a.) hydrogen bonds b.) the cell wall c.) peptide bonds d.) hydrophobic interactions

A

Which molecule is not a carbohydrate? a.) Lipid b.) Glycogen c.) Starch d.) Cellulose

A

Which of the following statements about monosaccharide structure is true? a.) Monosaccharides can be classified according to the spatial arrangement of their atoms. b.) All monosaccharides contain carbon, hydrogen, oxygen, and nitrogen atoms. c.) Aldoses and ketoses differ in the position of their hydroxyl groups. d.) A six-carbon sugar is called a pentose.

A

(5.7) You believe a bacterium is attaching to animal cells by binding to the carbohydrate portion of a specific glycoprotein. To test this hypothesis you pre-incubate the bacteria with various molecules and then test for inhibition of attachment to the animal cells. Which result supports the hypothesis that the bacteria recognize the carbohydrate component of the animal glycoprotein? a.) Pretreatment with the protein component alone prevents bacteria attachment to the animal cells. b.) Pretreatment with the carbohydrate component alone prevents bacteria attachment to the animal cells. c.) Pretreatment with the entire glycoprotein allows bacteria attachment to the animal cells. d.) Pretreatment with the entire glycoprotein prevents bacteria attachment to the animal cells.

B

Both carbohydrates and fats are used as fuel in cells, but fats store twice as much energy per gram as carbohydrates. Which statement best explains why? a.) Fats have more C-O bonds with high potential energy, and fewer C-C and C-H bonds with low potential energy. b.) Fats have more C-C and C-H bonds with high potential energy, and fewer C-O bonds with low potential energy. c.) Fats have more C-O bonds with low potential energy, and fewer C-C and C-H bonds with high potential energy. d.) Fats have more C-C and C-H bonds with low potential energy, and fewer C-O bonds with high potential energy.

B

How do the structures of glucose and galactose differ? a.) Glucose has more hydrogen and fewer oxygen atoms than galactose. b.) The spatial arrangement of the hydroxyl group on the fourth carbon is different. c.) Glucose is a hexose; galactose is a pentose. d.) Glucose is an aldose; galactose is a ketose.

B

Predict how this enzyme may be involved in human health. a.) Lysozyme helps to digest peptidoglycan in digestive tract. b.) Lysozyme helps to protect humans against bacterial infections. c.) Lysozyme helps to protect humans against viral infections. d.) Lysozyme makes human's saliva, tears and other excretions sterile.

B

Which complex carbohydrate contains only a-1,4-glycosidic linkages? a.) Amylopectin b.) Amylose c.) Glycogen d.) Cellulose

B

Which of these is a source of lactose? a.) sugar beets b.) milk c.) potatoes d.) sugar cane e.) starch

B

_____ is the most abundant organic compound on Earth. a.) Starch b.) Cellulose c.) Glycogen d.) Glucose e.) Lactose

B

glucose + glucose —> _____ by _____. a.) sucrose + water ... dehydration synthesis b.) maltose + water ... dehydration synthesis c.) cellulose + water ... hydrolysis d.) starch + water ... dehydration synthesis e.) lactose + water ... hydrolysis

B; Maltose is the disaccharide formed when two glucose molecules are linked by dehydration synthesis.

Select the statement that is incorrect. a.) Complex sugars are carbohydrates. b.) All carbohydrates have the general formula Cn(H2O)n. c.) Simple sugars are carbohydrates. d.) Simple sugars contain only carbon, oxygen, and hydrogen atoms.

B; This formula only applies to simple sugars, which are equal parts carbon and water. Complex sugars, which do not have this general formula, are also carbohydrates.

Dairy cattle were unknown in Thai culture until recently, and 97 percent of Thai people are lactose intolerant as adults. Which explanation for such widespread lactose intolerance is most likely correct? a.) The ability to digest sugar in milk is determined by environment, and most humans are not exposed to milk as a food source beyond childhood years. b.) There is no good explanation for this situation in humans. c.) Evolutionarily, producing an enzyme to break down a sugar that will never be encountered is wasteful. d.) Allergies are becoming more common in humans as more chemicals are being encountered during longer lifetimes.

C

How could two four-sugar oligosaccharides be structurally different even if both consist of two glucose monomers and two galactose monomers? a.) Only the sequence of monomers along the chain could vary. b.) One oligosaccharide could contain aldoses while the other contains ketoses. c.) The sequence of monomers along the chain or the location and geometry of glycosidic linkages could vary (or both). d.) Only the location and geometry of glycosidic linkages could vary.

C

Review the experiment shown in Figure 5.7. How would the results change if sperm attachment required only the protein portion of egg glycoproteins? a.) Only intact glycoprotein would exhibit significant attachment inhibition compared to the untreated control. b.) Only intact glycoprotein and pure carbohydrate would exhibit significant attachment inhibition compared to the untreated control. c.) Only intact glycoprotein and pure protein would exhibit significant attachment inhibition compared to the untreated control. d.) Intact glycoprotein, pure protein, and pure carbohydrate would all exhibit significant attachment inhibition compared to untreated control.

C; Pre-binding of sperm to either intact glycoprotein or pure protein would inhibit sperm-egg attachment.