Deck 5: An Introduction to Carbohydrates

Question 1

Lactose, a sugar in milk, is composed of one glucose molecule joined by a glycosidic linkage to one galactose molecule. How is lactose classified?

A) as a pentose
B) as a hexose
C) as a monosaccharide
D) as a disaccharide
E) as a polysaccharide

Answer 1

D

Question 2

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

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

Answer 2

A

Question 3

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 3

B

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 molecules contains at LEAST one peptide bond?

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

Question 6

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 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

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 9

The enzyme amylase can break glycosidic linkages between glucose monomers only if the monomers are the α form. Which of the following could amylase break down?

A) starch
B) cellulose
C) chitin
D) starch and chitin only
E) starch, cellulose, and chitin

Question 10

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 11

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 12

What role, if any, did polysaccharides play in chemical evolution?

A) Polysaccharides catalyzed chemical reactions.
B) Polysaccharides used complementary pairing between monosaccharides to copy themselves.
C) Glycosidic linkages formed spontaneously between monosaccharides.
D) Polysaccharides played little, if any, role in chemical evolution.

Question 13

A molecule with the chemical formula C6H12O6 is probably a ________.

A) fatty acid
B) polysaccharide
C) phospholipid
D) nucleic acid
E) monosaccharide

Question 14

The molecule shown in the accompanying figure is ________.

A) a hexose
B) a pentose
C) a phosphate
D) fructose
E) maltose

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 are all composed of highly branched fibers.

Question 16

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 17

The molecular formula for glucose is C6H12O6. What would be the molecular formula for a molecule made by linking three glucose molecules together by dehydration reactions?

A) C18H36O18
B) C18H32O16
C) C6H10O5
D) C18H30O15
E) C3H6O3

Question 18

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) the presence of sulfur groups

Question 19

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 20

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 21

If two molecules of the general type shown in the accompanying figure were linked together, carbon-1 of one molecule to carbon-4 of the other, the single molecule that would result would be ________.

A) maltose
B) fructose
C) glucose
D) galactose
E) sucrose

Question 22

The molecular formula for glucose is C6H12O6. What would be the molecular formula for a polymer made by linking 10 glucose molecules together by dehydration reactions?

A) C60H120O60
B) C6H12O6
C) C60H102O51
D) C60H100O50
E) C60H111O51

Question 23

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 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 carbohydrates are rich in energy because they are highly oxidized.
C) Carbohydrates are reduced molecules that have high-energy electrons.
D) This is an advertising gimmick that has no scientific evidence to support it.

Question 25

All of the following are polysaccharides EXCEPT ________.

A) lactose
B) glycogen
C) chitin
D) cellulose
E) amylopectin

Question 26

Which of the following categories includes all others in the list?

A) monosaccharide
B) disaccharide
C) starch
D) carbohydrate
E) polysaccharide

Question 27

Cellulose is ________.

A) a polymer composed of fructose monomers
B) a storage polysaccharide for energy in plant cells
C) used by plants to make glycogen
D) a major structural component of plant cell walls
E) a monomer of starch.

Question 28

What does the term "insoluble fiber" refer to on food packages?

A) cellulose
B) polypeptides
C) starch
D) amylopectin
E) chitin

Question 29

Humans can digest starch but not cellulose because ________.

A) humans have enzymes that can hydrolyze the α-glycosidic linkages of starch but not the β-glycosidic linkages of cellulose
B) humans have enzymes that can hydrolyze the β-glycosidic linkages of starch but not the α-glycosidic linkages of cellulose
C) starch monomers are joined by covalent bonds and cellulose monomers are joined by ionic bonds
D) the monomer of starch is glucose, while the monomer of cellulose is galactose
E) the monomer of starch is fructose, while the monomer of cellulose is glucose

Question 30

Which of the following polymers contain nitrogen?

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

Question 31

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

A) is a disaccharide
B) could be a glycoprotein
C) is a nucleic acid
D) could be cellulose or glycogen

Question 32

Which of the following is NOT a polymer?

A) glucose
B) starch
C) cellulose
D) chitin
E) DNA

Question 33

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 34

Starch and cellulose ________.

A) are polymers of glucose
B) are cis-trans isomers of each other
C) can be digested by humans
D) are used for energy storage in plants
E) are structural components of the plant cell wall

Question 35

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 36

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 α 1,4-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)

Question 37

How 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 used by mitochondria to bond to substrates and catalyze reactions.
D) Carbohydrates have no role in containing or displaying information for cells.

Question 38

Which of the following would you expect to have the most free energy per gram? The most free energy per gram would be found in a molecule with ________.

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

Question 39

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 40

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 an organism got wet. Which of the following carbohydrates would you expect to be most soluble in water?

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

Question 41

Use the following paragraph to answer the corresponding question.
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 α-1,4-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 a glycoprotein that has its terminal NAG removed.

Question 42

A primary function of carbohydrates attached to the glycoproteins and glycolipids of animal cell membranes is to ________.

A) facilitate diffusion of molecules down their concentration gradients
B) actively transport molecules against their concentration gradients
C) maintain the integrity of a fluid mosaic membrane
D) maintain membrane fluidity at low temperatures
E) mediate cell-cell recognition

Question 43

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, α-glucose.
D) Structural carbohydrates are long strands, which are chemically linked into a network.

Question 44

Chitin is a major component of the ________.

A) cell walls of bacteria
B) hydrostatic skeletons of earthworms
C) exoskeleton of insects
D) body hairs of mammals
E) skeleton in birds