Deck 20: Biochemistry the Compounds of Life

Question 1

Which statement about chirality in amino acids is NOT correct?

A)An amino acid is chiral if it has a carbon atom bonded to four different groups.
B)An amino acid is chiral if it cannot be superimposed on its mirror image.
C)Almost all of the amino acids found in human proteins except glycine, are chiral.
D)The $\alpha$ -carbon in an amino acid is a chiral center.
E)Almost all the amino acids found in human proteins are dextrorotary enantiomers and rotate plane-polarized light to the right.

Answer 1

Almost all the amino acids found in human proteins are dextrorotary enantiomers and rotate plane-polarized light to the right.

Question 2

At a physiological pH of 7.4, amino acids exist as zwitterions because the pK_a of the -NH₃+ group is ____7.4, and the pK_a of the -COOH group is____ 7.4.

A)greater than; less than
B)less than; greater than
C)greater than; greater than
D)less than; less than
E)equal to; equal to

Answer 2

greater than; less than

Question 3

Which of the following, if any, can be classified as an amino acid?
I.
II.

III.

IV.

A)III and IV
B)I and II
C)I only
D)II only
E)III only

Answer 3

III and IV

Question 4

Which statement regarding the common amino acids found in human proteins is NOT correct?

A)The $\alpha$ -carbon is bonded to one of 20 different R groups.
B)All of the amino acids have side groups that contain only carbon and hydrogen.
C)Several of the amino acids have side groups containing the carboxylic acid functional group.
D)Several of the amino acids have weakly basic side groups that contain nitrogen.
E)All of the $\alpha$ -amino acids are have polar functional groups.

Question 5

This molecule is a(n)

A)lipid.
B)fatty acid.
C)amino acid.
D)nucleic acid.
E)saccharide.

Question 6

Aspartame exists as a zwitterion at physiological pH with a____ carboxylic group and a ____amine group.

A)deprotonated; protonated
B)protonated; deprotonated
C)protonated; protonated
D)deprotonated; deprotonated
E)functionalized; defunctionalized

Question 7

Which statement about amino acid enantiomers is NOT correct?

A)An enantiomer cannot be superimposed on its mirror image.
B)Enantiomers are examples of stereoisomers.
C)A solution of an enantiomer rotates the plane of polarized light.
D)Enantiomers are designated by the prefixes D and L.
E)All the chiral amino acids in our bodies are mixtures of enantiomers.

Question 8

Which of the following functional groups is NOT found in an amino acid?

A)an amide
B)an amine
C)a carboxylic acid
D)a carbonyl
E)All of these are found.

Question 9

Isomers that cannot be superimposed on their mirror images are called

A)geometric isomers.
B)structural isomers.
C)functional isomers.
D)enantiomers.
E)constitutional isomers.

Question 10

A peptide bond is the result of a condensation reaction between

A)two carboxylic acid groups on different amino acids.
B)an amino group on one amino acid and the carboxylic acid group on a second amino acid.
C)two amino groups on different amino acids.
D)an amino group and a carboxylic acid group on the same amino acid.
E)an amino group and a carboxylic acid group producing a zwitterion.

Question 11

In an experiment, 100 mL of a 0.1 M solution of methionine is titrated using 0.1 M NaOH.Using this information, along with the titration curve shown, which of the following statements is NOT correct?

A)At low pHs, the majority of the amino acid present is fully protonated.
B)The pK_a of the protonated amine group seems to be a little greater than 10.
C)When the pH reaches the physiological value of 7.4, the carboxylic acid group is essentially deprotonated.
D)The K_a of the -COOH group appears to be between 5 *10^-3 and 8*10^-3.
E)Methionine appears to have a neutral side group, as there seem to be two equivalence points evident on the titration curve.

Question 12

An organic molecule present naturally in a living system is called a

A)hydrocarbon.
B)ribosome.
C)hormone.
D)porphyrin.
E)biomolecule.

Question 13

Amino acids are bonded together via____ bonds.

A)glycosidic
B)peptide
C)hydrogen
D)ionic
E)van der Waals

Question 14

At a physiological pH of 7.4, amino acids exist as zwitterions.At a very low pH in an acid solution), both the amine group and the carboxylic acid group on an amino acid are protonated.Which acid group is the stronger acid?

A)(-NH₂)
B)(-NH₃+)
C)(-COOH)
D)(-COO-)
E)(-H₃O+)

Question 15

At a physiological pH of 7.4, amino acids exist as zwitterions.At a very low pH( in an acid solution), both the amine group and the carboxylic acid group on an amino acid are protonated.Therefore, the following must be true: the pK_a of the ___group is larger than the pK_a of the ____group.

A)protonated amine group; carboxylic acid group
B)carboxylic acid group; protonated amine group
C)amine group; carbonate group
D)hydronium ion group; hydroxyl ion group
E)carbonate group; amine group

Question 16

Amino acids that humans cannot synthesize are called _____amino acids.

A)animal
B)legume
C)essential
D)required
E)perfect

Question 17

Which of the following are NOT considered biopolymers?

A)proteins
B)polysaccharides
C)nucleic acids
D)lipids
E)All of these are biopolymers.

Question 18

An $\alpha$ -amino acid is one in which the amine group and the carboxylic acid group are attached to

A)different carbon atoms.
B)different nitrogen atoms.
C)the same carbon atom.
D)the terminal carbon of the molecule.
E)neighboring carbon atoms.

Question 19

Which statement is NOT correct? A chiral amino acid

A)is an enantiomer.
B)can be superimposed on its mirror image.
C)has four different groups bonded to the same carbon atom.
D)has properties different from those of its mirror image.
E)rotates the plane of polarized light.

Question 20

Which of the following are NOT amino acids?
I.
II. III.
IV.

A)III and IV
B)I and II
C)I only
D)II only
E)III only

Question 21

Which of the following statements regarding enzymes is NOT correct?

A)An enzyme is a biological catalyst that is usually a protein.
B)The active site of an enzyme can only interact with its intended substrate.
C)The ability of an enzyme to act effectively is heavily dependent on environmental factors, such as temperature and pH.
D)Most biological enzymes are highly specific, catalyzing one type of reaction only.
E)When the substrate binds to an enzyme, the enzyme's three-dimensional structure may change as the reaction proceeds.

Question 22

The three-dimensional structure of a multi-subunit protein, including how the subunits fit together, is described by the term

A)primary structure.
B)secondary structure.
C)tertiary structure.
D)long-range structure.
E)quaternary structure.

Question 23

Which functional group links amino acids together to form proteins?

A)amine
B)ester
C)ether
D)amide
E)phosphate

Question 24

A polypeptide consists of up to ____amino acids that bond together.

A)5
B)10
C)20
D)50
E)100

Question 25

When the number of amino acids linked together in a peptide reaches about 50 to 75, its classification usually transitions from ____to____ .

A)peptide; oligopeptide
B)oligopeptide; polypeptide
C)minipeptide; megapeptide
D)polypeptide; protein
E)hypoprotein; hyperprotein

Question 26

Which of the following is NOT a description of the secondary structure of a protein?

A)( $\alpha$ -helix)
B)( $\beta$ -pleated sheet)
C)random coil
D)sequence of amino acids in the protein
E)geometric patterns formed by amino acids

Question 27

The assembly and interaction of coils and sheets in a polypeptide to produce the overall three-dimensional shape are described by the term

A)primary structure.
B)secondary structure.
C)tertiary structure.
D)long-range structure.
E)quaternary structure.

Question 28

Which functional group is NOT present in this tripeptide?

A)amide
B)amine
C)carbonyl
D)ester
E)methyl

Question 29

The first stage in the folding process of proteins, which occurs as a result of a combination of intermolecular forces, is

A)the primary structure.
B)the secondary structure.
C)the tertiary structure.
D)the ordering structure.
E)the quaternary structure.

Question 30

Which of the following statements regarding the sequence of amino acids in proteins is NOT correct?

A)The solubility of proteins in water depends on their sequence of amino acids.
B)Sickle cell anemia is an example of the effect that the primary structure of a protein can have on its function.
C)The effect of substituting one amino acid for another in a protein can depend heavily on the polarity of the side groups involved.
D)Two proteins containing the same numbers and types of amino acids can have different functions.
E)Changing a single amino acid in a protein has little impact on its properties.

Question 31

Which one of the following is best associated with proteins?

A)trigylcerides
B)saccharides
C)amino acids
D)hydrocarbon chains
E)nucleotides

Question 32

The $\alpha$ -helix and $\beta$ -pleated sheet are examples of

A)primary structure.
B)secondary structure.
C)tertiary structure.
D)arrangement structure.
E)quaternary structure.

Question 33

Which of the following is characteristic of an $\alpha$ -helix?

A)Hydrogen bonds between -NH groups on one part of the chain and C=O groups on nearby amino acids cause the protein to coil with the amino acids' R groups pointing outward.
B)Dipole-dipole interactions between polar side groups in one part of the chain and C=O or -NH groups on nearby amino acids cause the protein to coil with the amino acids' R groups pointing outward.
C)London forces between hydrophobic regions in the amino acid sequence cause the protein to coil up in order to have hydrophilic regions of the chain point outward.
D)Single-strand proteins interact via hydrogen bonds, forming coils in which polar side groups point outward.
E)Side-by-side zigzag chains of amino acids held together by hydrogen bonds aggregate to form a coiled structure held together by intermolecular forces.

Question 34

Which of the following is characteristic of a $\beta$ -pleated sheet?

A)Hydrogen bonds between -NH groups on one part of the chain and C=O groups on nearby amino acids cause the protein to fold up on itself with the amino acids' R groups pointing outward.
B)Ion-ion interactions between side groups on different parts of the chain cause the protein to fold up on itself to forms sheets of amino acid chains.
C)London forces between hydrophobic regions in the amino acid sequence cause the protein to fold up on itself in order to have hydrophilic regions of the chain point outward.
D)Side-by-side zigzag chains of amino acids held together by hydrogen bonds aggregate to form a continuous sheet.
E)Single-strand proteins form peptide linkages between chains that cause the chains to fold on top of one another, forming a continuous sheet.

Question 35

The following reaction produces a peptide.Which statement about this reaction is NOT correct?

A)In this reaction, an amino group reacts with a carboxylic acid group.
B)This condensation reaction produces a peptide bond.
C)An amide group is formed in this reaction.
D)The peptide shown is the only possible product produced by this reaction.
E)Two amino acids are linked together by this reaction.

Question 36

Compounds that diminish or destroy the effectiveness of an enzyme are called

A)substrates.
B)decomposers.
C)deactivators.
D)inhibitors.
E)negators.

Question 37

The molecule drawn below is an example of an)

A)nucleic acid base.
B)peptide.
C)carbohydrate.
D)fatty acid.
E)amino acid.

Question 38

How many amino acids are contained in the following peptide?

A)2
B)3
C)4
D)5
E)6

Question 39

The primary structure of a protein is

A)the $\alpha$ -helix structure of the protein.
B)the $\beta$ -pleated sheet structure of the protein.
C)the sequence of amino acids in the protein.
D)a list of the amino acids in the protein along with the number of times each occurs.
E)the specific arrangement of $\alpha$ -helices and $\beta$ -pleated sheets in the protein.

Question 40

What is the name of the peptide shown?

A)valylseylalanine
B)alaylserylvaline
C)alasergylvaline
D)valinylglycinylserinylalanine
E)alanylserylglycylvaline

Question 41

The cyclization of fructose forms a

A)four-membered ring.
B)five-membered ring.
C)six-membered ring.
D)seven-membered ring.
E)double ring.

Question 42

Which one of the following is best associated with carbohydrates?

A)amino acids
B)phosphate linkages
C)amide bonds
D)saccharides
E)hydrocarbon rings

Question 43

Glucose is shown below.Number the carbon atoms 1-6 from top to bottom.In the cyclization reaction, a bond is formed to C1 by an oxygen lone pair on the OH bonded to

A)C2.
B)C₃.
C)C4.
D)C5.
E)C₆.

Question 44

Which of the following chemical formulas is probably that of a disaccharide?

A)CH₂O
B)C₆H₁₀O₅
C)C₁₂H₂2O11
D)C₂H₄O₂
E)C₃H₆O₃

Question 45

In its ring structure, which functional groups are present in glucose?

A)aldehyde and alcohol
B)aldehyde and carboxyl
C)alcohol and ketone
D)amino and alcohol
E)ether and alcohol

Question 46

A monosaccharide an empirical formula of

A)CH₂O.
B)C₆H₁₂O₆.
C)C₁₂H₂2O11.
D)C₂H₄O₂.
E)C₃H₆O₃.

Question 47

The molecule drawn below is an example of a a(n)

A)nucleic acid base.
B)amino acid.
C)carbohydrate.
D)fatty acid.
E)lipid.

Question 48

The molecule drawn below is an example of a

A)nucleic acid base.
B)dipeptide.
C)disaccharide.
D)fatty acid.
E)lipid.

Question 49

Which one of the following statements about biomolecules is NOT correct?

A)Table sugar (sucrose) is a disaccharide made of glucose and fructose.
B)Starch and cellulose are polysaccharides made from glucose.
C)A glycosidic linkage in polysaccharides is an ether group.
D)Cellobiose is a disaccharide composed of two glucose monomers.
E)All biomolecules containing glucose monomers can be readily digested by humans.

Question 50

Table sugar is

A)glucose.
B)lactose.
C)a disaccharide of glucose and fructose.
D)a glucose-glucose disaccharide.
E)cellobiose.

Question 51

Table sugar is

A)sucrose.
B)fructose.
C)glucose.
D)sucralose.
E)maltose.

Question 52

Sucralose, the active ingredient in an artificial sweetener, Splenda, is shown below.Sucralose is advertised as being made from table sugar.What is the main difference between sucrose table sugar) and sucralose?

A)Sucralose is a disaccharide, whereas sucrose is a monosaccharide.
B)Sucralose has a six-membered and a five-membered ring, unlike the two six-membered rings in sucrose.
C)Sucralose has a glycosidic bond between the two saccharide units, unlike the C-C bond in sucrose.
D)Sucralose contains chlorine atoms, whereas sucrose does not.
E)Sucralose has a six-membered and a five-membered ring, unlike the two five-membered rings in sucrose.

Question 53

In its linear form, which functional groups are present in glucose?

A)aldehyde and alcohol
B)aldehyde and carboxyl
C)alcohol and ketone
D)amino and alcohol
E)ether and alcohol

Question 54

Which statement is NOT correct? Sucrose is

A)used for table sugar.
B)a disaccharide.
C)consists of glucose and fructose with a glycosidic bond.
D)a synonym for glucose.
E)formed in a condensation reaction that eliminates water.

Question 55

Which of the following is a monosaccharide?

A)sucrose
B)glucose
C)starch
D)cellulose
E)cellobiose

Question 56

The cyclization of glucose forms a(n)

A)four-membered ring.
B)five-membered ring.
C)six-membered ring.
D)seven-membered ring.
E)eight-membered ring.

Question 57

Which of the following chemical formulas is probably that of a monosaccharide?

A)CH₂O
B)C₆H₁₀O₂
C)C₁₂H₂2O11
D)C₂H₄O₂
E)C₆H₁₂O₆

Question 58

Table sugar is

A)glucose.
B)fructose.
C)cellobiose.
D)a monosaccharide.
E)a disaccharide.

Question 59

A carbohydrate might have a molecular formula of

A)CH₂O.
B)C₆H₁₂O₆.
C)C₆H₁₀O₂.
D)C₂H₄O₂.
E)C₃H₆O₃.

Question 60

Which of the following statements regarding carbohydrates is NOT correct?

A)Most organisms use mono- and disaccharides for short-term energy storage.
B)Many plants use cellulose as structural support.
C)Carbohydrates and carbohydrate derivatives aid in molecular recognition, particularly at the surface of cells.
D)Starch is the most abundant energy-storage molecule in plants.
E)Humans can use starch as an energy source but not cellulose, even though both molecules contain glucose monomers.

Question 61

Estradiol, like cholesterol, is

A)a nucleic acid base.
B)an amino acid.
C)a carbohydrate.
D)a fatty acid.
E)a lipid.

Question 62

To produce ethanol from corn i.e., starch) to use as fuel or drink, the starch first must be decomposed to glucose through a process called

A)fermentation.
B)distillation.
C)hydrolysis.
D)combustion.
E)oxidation.

Question 63

The TCA cycle

A)is responsible for the production of carbohydrates via photosynthesis.
B)represents a series of chemical reactions that break down cellulose to produce glucose.
C)represents a series of chemical reactions that assist in extracting energy from glucose.
D)describes how enzymes act as catalysts.
E)describes the unfolding of proteins.

Question 64

The cyclization reaction of fructose is different from that of glucose because

A)a ketone is formed.
B)a bond is formed to a carbonyl carbon instead of to a methyl carbon.
C)the aldehyde group migrates to a new position.
D)a five-membered ring instead of a six-membered ring is formed.
E)fructose has only five carbon atoms total instead of six, as in glucose.

Question 65

Which statement is NOT correct? Starch and cellulose

A)are polysaccharides.
B)have monosaccharides joined by glycosidic bonds.
C)are a major source of biomass.
D)are stereoisomers made from glucose monomers.
E)are equally easily hydrolyzed to produce glucose.

Question 66

Lipids

A)contain a carboxyl group.
B)are typically insoluble in water.
C)are esters of glycerol and fatty acids.
D)are composed of carbon and hydrogen.
E)are solids under normal conditions.

Question 67

Which one of the following is best associated with lipids?

A)amino acids
B)saccharides
C)ribose units
D)ether linkages
E)fatty acids

Question 68

A glycosidic bond links two sugar molecules in carbohydrates.This linkage is associated with what functional group?

A)alcohol
B)amide
C)ester
D)aldehyde
E)ether

Question 69

A key step in the TCA cycle involving pyruvate ion results in the formation of______ when insufficient oxygen is present.

A)methane, carbon dioxide, and water
B)methanol and water
C)acetyl-coenzyme A
D)carbon dioxide and water
E)ethanol and carbon dioxide

Question 70

After glucose is oxidized to pyruvate ion, yeast cells growing under low-oxygen conditions convert pyruvate to

A)methane, carbon dioxide, and water.
B)methanol and water.
C)acetyl-coenzyme A.
D)carbon dioxide and water.
E)ethanol and carbon dioxide.

Question 71

Converting renewable biomass into fuel to reduce fossil fuel usage is an idea gaining support, despite the fact that energy produced through biomass conversion will always be small compared to our total needs.To be viable, the process must be cost effective, not be subsidized by taxpayer support, and not reduce the food supply.In a research lab, project A deals with $\alpha$ -glucoside hydrolysis of starches, whereas project B deals with $\beta$ -glucoside hydrolysis of cellulose.What value would you place on these projects and why?

A)Project A is more valuable because improving the efficiency of starch hydrolysis will increase the effectiveness of our edible corn for fuel programs and reduce the need for taxpayer subsidies.
B)Project B is more valuable because the hydrolysis of cellulose, which is not edible, to produce glucose and ethanol currently is not economically viable.
C)Both are valuable because any research along these lines deserves equitable support.
D)Neither is valuable because they do not address climate change.
E)The viability of both projects is questionable, so neither merits serious consideration.

Question 72

An ether linkage connects monomers in

A)carbohydrates.
B)nucleic acids.
C)proteins.
D)lipids.
E)steroids.

Question 73

Glucose and fructose undergo a(n) _____reaction in the formation of sucrose.

A)sugarization
B)precipitation
C)condensation
D)combustion
E)addition

Question 74

Glucose is to starch as

A)pure gold is to 14 karat gold.
B)a trumpet is to a tuba.
C)a leaf is to a tree.
D)a link is to a chain.
E)a tomato is to a potato.

Question 75

Hydrolysis is

A)any reaction involving water as a reactant.
B)always endothermic.
C)the process that forms a glycosidic linkage.
D)the breaking of a bond to produce hydrogen gas.
E)the breaking of a bond by the addition of water.

Question 76

Glucose is to cellulose as

A)pure gold is to 14 karat gold.
B)a peptide is to a polypeptide.
C)a leaf is to a tree.
D)a trumpet is to a tuba.
E)a tomato is to a potato.

Question 77

Glycerides are formed between

A)glycerol and inorganic acids.
B)glucose and long-chain fatty acids.
C)glycerol and long-chain fatty acids.
D)glycerol and any carboxylic acid.
E)glucose, fructose, and sucrose.

Question 78

What is the linkage that forms between two monosaccharides in a polysaccharide?

A)C - CH₂ - C
B)C - O - O - C
C)C - O - C
D)C =C
E)C - N - C

Question 79

In glycolysis, _____is converted into pyruvic acid.

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

Question 80

Which of the following is NOT categorized as a lipid?

A)fatty acid esters
B)cholesterol
C)fats
D)cellulose
E)oils