Deck 5: An Introduction to Carbohydrates

Question 1

How is carbohydrate use similar or different between plants and animals? Select the true statement below.

A)In animals,carbohydrates have mainly a structural role,while in plants,carbohydrates are mainly used to store energy.
B)Carbohydrates catalyze reactions in both animals and plants.
C)Carbohydrates play a structural role in some types of animals and in all plants.
D)None of answers A-C are correct.

Answer 1

C

Question 2

How do the α and β forms of glucose differ?

A)Their ring structures differ in the location of a hydroxyl group.
B)Their linear structures differ in the location of a hydroxyl group.
C)The α form can be involved in 1,4 and 1,6 glycosidic linkages;the β form can participate only in 1,4 linkages.
D)The oxygen atom inside the ring is located in a different position.

Answer 2

A

Question 3

Peptidoglycan forms sheets that stiffen the cell walls of bacteria.How is the formation of sheets possible?

A)The polysaccharides in peptidoglycan are highly branched and form a network.
B)The glycosidic linkages between monosaccharides in peptidoglycan are extraordinarily strong.
C)Individual strands are joined by peptide bonds a type of covalent bond.
D)The polysaccharides in peptidoglycan form helical structures,as in cellulose.

Answer 3

C

Question 4

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)Allergies are becoming more common in humans as more chemicals are being encountered during longer lifetimes.
B)Evolutionarily,producing an enzyme to break down a sugar that will never be encountered is wasteful.
C)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.
D)There is no good explanation for this situation in humans.

Question 5

Which of the following can vary among monosaccharides?

A)the number of carbon atoms
B)the presence of a carbonyl group
C)the presence of hydroxyl groups
D)all of the above

Question 6

Which of the following do starch and cellulose have in common?

A)the type of glycosidic linkage used
B)the size of their monosaccharide subunits
C)the amount of hydrogen bonding that occurs between parallel strands
D)their main function in plants

Question 7

Scientists believe polysaccharides played little role,if any,in chemical evolution.Which of the following is true of polysaccharides,which leads scientists to discount them as the first life-forms?

A)They catalyze chemical reactions.
B)There is complementary pairing between monosaccharides,so they can provide the information for copying themselves.
C)Glycosidic linkages form spontaneously between monosaccharides.
D)None of A,B,or C is true-they are all false.

Question 8

A glycosidic linkage is analogous to which of the following in proteins?

A)an amino group
B)a peptide bond
C)a disulfide bond
D)a β-pleated sheet

Question 9

What is the major structural difference between starch and glycogen?

A)the types of monosaccharide subunits in the molecules
B)the type of glycosidic linkages in the molecule
C)whether glucose is in the α or β form
D)the amount of branching that occurs in the molecule

Question 10

What is the difference between an aldose sugar and a ketose sugar?

A)the number of carbons
B)the position of the hydroxyl groups
C)the position of the carbonyl group
D)one is a ring form,the other is a linear chain

Question 11

Which of the following linkages would you expect to find at a branch point in glycogen or amylopectin?

A)α-1,4-glycosidic linkage
B)β-1,4-glycosidic linkage
C)α-1,6-glycosidic linkage
D)β-1,6-glycosidic linkage

Question 12

Carbohydrates have been shown to form _____.

A)only in biotic conditions (inside living cells)
B)in biotic and abiotic conditions,but only if nucleotides and RNA have already formed
C)in biotic and abiotic conditions,including outer space
D)only in biotic conditions,when enough free energy is available to allow their formation

Question 13

Which of the following structural features is common to cellulose,chitin,and peptidoglycan?

A)They are all composed of glucose in either the α or β form.
B)They all contain peptide bonds.
C)They can all form bonds between polymer chains that create parallel strands.
D)They are all composed of highly branched fibers.

Question 14

Glucose (C₆H₁₂O₆)has a single carbonyl group (-C=O)in its linear form.Based on the number of oxygen atoms in glucose,how many hydroxyl groups (-OH)would you expect glucose to have?

A)6
B)5
C)3
D)1

Question 15

Enzymes that readily break starch apart cannot hydrolyze the glycosidic linkages found in cellulose.Why is this logical?

A)The geometry of the bonds is different,and the shapes of enzyme active sites are highly specific.
B)Starch is held together by hydrogen bonding,not covalent bonding.
C)Cellulose molecules are highly branched,and enzymes are too bulky to fit.
D)Starch is held together by peptide bonds,not glycosidic linkages.

Question 16

Which of these best reflects the following relationship:
Monosaccharide versus polysaccharide?

A)glucose versus glycogen
B)glucose versus fructose
C)1,4-glycosidic linkage versus 1,6-glycosidic linkage
D)α-linkage versus β-linkage

Question 17

Which of the following carbohydrates contains a peptide bond?

A)Carbohydrates don't contain peptide bonds;only proteins do.
B)cellulose
C)chitin
D)peptidoglycan
E)glycogen

Question 18

Which polysaccharide is an important component in the structure of many animals and fungi?

A)chitin
B)cellulose
C)peptidoglycan
D)amylose

Question 19

You isolate an organic molecule that contains C,H,O,N,and S.This molecule _____.

A)is definitely a sugar
B)could be a glycoprotein
C)is definitely a nucleic acid
D)is definitely a protein that is not glycosylated

Question 20

Compare the molecular formula of a carbohydrate (CH₂O)n with that of carbon dioxide (CO₂).What does the presence of hydrogen atoms in carbohydrates indicate?

A)Carbohydrates are more reduced than carbon dioxide.
B)Carbohydrates are more oxidized than carbon dioxide.
C)Every carbon atom in a carbohydrate is bonded to four different atoms.
D)Carbohydrates contain a carbonyl functional group.

Question 21

If you were going to develop a new antibiotic against bacteria,you would probably need to become an expert on which of these carbohydrates?

A)glycogen
B)chitin
C)peptidoglycan
D)cellulose
E)starch

Question 22

Bacteria,insects,and plants use carbohydrates to build structures.Which of the following is true of structural carbohydrates?

A)Different types of pentose monomers form the basis of all carbohydrate-based structures.
B)Structural carbohydrates show a high degree of branching.
C)All structural carbohydrates are made from the same monomer,a-glucose.
D)Structural carbohydrates are long strands of monomers;the strands are chemically linked together to form a network.
E)None of A,B,C,or D is true.

Question 23

The chemical formula for fat is C₁₂H₂₄O₃.The analogous chemical formula for carbohydrates is C₁₂ H ₂₄ O₁₂.Given the differences in their chemical formulas,why do you think that plants generally store their
energy in the form of carbohydrates,but animals generally store their energy in the form of fats?

Question 24

Which of the following best explains why "carbs" (carbohydrates)are advertised by manufacturers of candy bars and sports drinks as a "quick energy boost"?

A)The energy in them can be stored as fat,which has high energy per unit weight.
B)The carbons in carbs are rich in energy because they are highly oxidized.
C)Carbs are reduced molecules that have high-energy electrons.
D)This is an advertising gimmick that has no scientific evidence to support it.

Question 25

Cell walls are used by many different organisms for protection from their environment and structural support.These cell walls must obviously be insoluble in water;otherwise,they would dissolve the first time the organism got wet.Which of the following carbohydrates would you expect to be the most soluble in water?

A)starch
B)peptidoglycan
C)cellulose
D)chitin

Question 26

Use the following paragraph to answer the corresponding question(s).
Masatomo Kawakubo et al.reported in Science in August 2004 that the human stomach contains a natural,carbohydrate-based antibiotic that probably protects a large portion of the population from various diseases caused by the bacterium Helicobacter pylori.This bacterium has been linked to peptic ulcers,gastritis,and stomach cancer.This naturally occurring antibiotic is described by Kawakubo as having a terminal α1,4-linked N-acetylglucosamine (NAG),and it acts by inhibiting the biosynthesis of a major component of the cell wall in H.pylori.[Source: M.Kawakubo et al. ,Science 305 (2004): 1003.]
Refer to the paragraph about Kawakubo's group.Kawakubo's group created a glycoprotein with a terminal NAG (i.e. ,a protein with NAG attached to its end).Their hypothesis is that the terminal NAG and not the protein component is responsible for the damage to the cell wall in H.pylori.What would be the most appropriate control for testing this hypothesis?

A)Grow H.pylori in a test tube (in vitro)with no glycoprotein.
B)Destroy the H.pylori by exposing them to a hypotonic solution.Then add the glycoprotein and observe.
C)Expose other species of bacteria to the glycoprotein.
D)Grow H.pylori in a test tube with glycoprotein that has its terminal NAG removed.

Question 27

Which of the following molecules would you expect to have the most free energy per gram?

A)one with carbon and hydrogen atoms only
B)one with carbon,hydrogen,and oxygen atoms only
C)one with a variety of atoms that are found in cells
D)one with hydrogen and oxygen atoms only

Question 28

Why do plants require sunlight?

A)Sunlight helps plants break down their food products so they can extract the energy stored in them.
B)Sunlight energy can be used by plants to reduce the carbon atoms in carbon dioxide.
C)Sunlight oxidizes carbon dioxide and water to form glucose.
D)Sunlight can be used directly by plants to perform a number of physiological processes.

Question 29

Use the following paragraph to answer the corresponding question(s).
Masatomo Kawakubo et al.reported in Science in August 2004 that the human stomach contains a natural,carbohydrate-based antibiotic that probably protects a large portion of the population from various diseases caused by the bacterium Helicobacter pylori.This bacterium has been linked to peptic ulcers,gastritis,and stomach cancer.This naturally occurring antibiotic is described by Kawakubo as having a terminal α1,4-linked N-acetylglucosamine (NAG),and it acts by inhibiting the biosynthesis of a major component of the cell wall in H.pylori.[Source: M.Kawakubo et al. ,Science 305 (2004): 1003.]
In what way do carbohydrates contain and/or display information for cells?

A)Carbohydrates store information in the nucleus.
B)Carbohydrates contain and display information at the cell surface.
C)Carbohydrates display information in order to bond to substrates and catalyze reactions.
D)Actually,carbohydrates have no role in containing or displaying information for cells.

Question 30

Use the following paragraph to answer the corresponding question(s).
Masatomo Kawakubo et al.reported in Science in August 2004 that the human stomach contains a natural,carbohydrate-based antibiotic that probably protects a large portion of the population from various diseases caused by the bacterium Helicobacter pylori.This bacterium has been linked to peptic ulcers,gastritis,and stomach cancer.This naturally occurring antibiotic is described by Kawakubo as having a terminal α1,4-linked N-acetylglucosamine (NAG),and it acts by inhibiting the biosynthesis of a major component of the cell wall in H.pylori.[Source: M.Kawakubo et al. ,Science 305 (2004): 1003.]
Which of the following structures is most consistent with Kawakubo's description of this antibiotic?

A)
B)
C)
D)