Deck 5: An Introduction to Carbohydrates

Question 1

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

Answer 1

B

Question 2

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

Answer 2

C

Question 3

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

Answer 3

A

Question 4

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 5

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 6

Which of the following sugars might have the formula C₆H₁₂O₆?

A)triose
B)pentose
C)hexose
D)heptose

Question 7

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.

Question 8

The term carbohydrate is appropriate because of which of the following characteristics of sugars?

A)They all have the general formula (CH₂O)n.
B)They all have the general formula (C₂H₂O₂)n.
C)They all have the general formula (C₂HO)n.
D)They all have the general formula (CHO₂)n.

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

Synthesis of larger sugars has allowed us to study them more in depth.Which of the following are potential benefits/reasons why we would want to study oligosaccharides in detail?

A)Oligosaccharides are present on cell surfaces and are part of cell identity mechanisms.
B)Oligosaccharides are embedded in the cell membrane and help transport molecules across the membrane.
C)Oligosacchrides are one of the information molecules of the cell.
D)Oligosaccharides form the part of the membrane bilayer that controls membrane permeability.

Question 11

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 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

You like to add sugar to your coffee.Why would you need 1 teaspoon of table sugar to make it as sweet as only 1/8 of a teaspoon of an artificial sweetener?

A)Artificial sweeteners bind to a wider variety of receptors that detect sweetness,whereas table sugar only binds to one.
B)Artificial sweeteners have a greater affinity for the receptor that detects sweetness relative to table sugar.
C)Artificial sweeteners expand in the body once they encounter certain enzymes.

Question 14

Given that individuals with phenylketonuria are unable to metabolize phenylalanine,which of the following is most likely to be true in terms of what food items they should avoid?

A)all food with phenylalanine
B)all foods containing aspartame because it is artificial
C)all foods containing any artificial sweeteners because they are not natural

Question 15

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 all form highly branched fibers.

Question 16

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.

Question 17

Why do artificial sweeterns have less calories than sucrose and fructose,but still taste sweet?

A)They bind to specific taste receptor,but are quickly metabolized by the body.
B)They do not bind to any receptors and are quickly eliminated from the body.
C)They bind to a specific taste receptor,but do not have any ATP.
D)They bind to ATP,which then binds to the taste receptor.

Question 18

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 19

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 20

Scientists believe polysaccharides played little role,if any,in chemical evolution.Which of the following is not true of polysaccharides,leading scientists to discount them as the first life-forms?

A)They are incapable of catalyzing chemical reactions.
B)Because there is no complementary pairing between monosaccharides,they cannot provide the information for copying themselves.
C)The formation of glycosidic linkages between monosaccharides has been observed only with complex enzymes that would have come after chemical evolution-during biological evolution.
D)Polysaccharides are polymers,meaning they contain many monomer subunits.Polymers have never been observed to form,in any type of molecule,under laboratory conditions.

Question 21

If you were going to develop a new antibiotic,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

Which of the following enzymes catalyzes the hydrolysis of α-glycosidic linkages in glycogen?

A)amylase
B)phosphorylase
C)glycolase

Question 23

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 24

Which of the following polysaccharides is made up of parallel strands joined together by peptide bonds?

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

Question 25

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 26

In animals,the role of carbohydrate polymers is primarily

A)body protection.
B)information storage.
C)energy storage.
D)enzymes.

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

Which of the following polysaccharides is made up of highly branched helices?

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

Question 29

When an insect is crushed,it creates a crunching sound.What carbohydrate is the most likely source of this sound?

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

Question 30

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 31

Why do endurance athletes practice "carbohydrate loading," meaning to eat massive amounts of starch in the days leading up to a long race?

A)Starch is used as a building block for the synthesis of many other molecules.
B)Starch provides dietary fiber or "roughage" that aids digestion.
C)Carbohydrates are reduced molecules that can provide the chemical energy required during exercise.
D)Starch can be used to synthesize cellulose and build up the cell walls of muscles.

Question 32

Which of the following polysaccharides is made up of parallel strands joined together by hydrogen bonds?

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

Question 33

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 34

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 35

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 36

Which of the following structures is most consistent with Kawakubo's description of this antibiotic?

A)
B)
C)
D)

Question 37

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 38

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

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

Question 39

Which of the following enzymes catalyzes the hydrolysis of α-glycosidic linkages in starch?

A)amylase
B)phosphorylase
C)glycolase

Question 40

An important step in utilizing complex carbohydrates as an energy source is to break their glycosidic linkages.This is necessary because the digestive system cannot absorb any carbohydrates larger than a monosaccharide.Using information in your textbook (Chapter 5 and the chapters on digestion),compile a list of at least five enzymes that can accomplish this.Identify each enzyme's substrate and reaction products.You may include enzymes found in any organism.