Deck 3: Nucleic Acids, Proteins, and Enzymes

Question 1

According to the principle of complementary base pairing,purines always pair with

A) deoxyribose sugars.
B) uracil.
C) pyrimidines.
D) adenine.
E) guanine.

Answer 1

C

Question 2

The 5'-carbon of deoxyribose in DNA is attached to

A) adenine.
B) a phosphate group.
C) guanine.
D) a pyrimidine.
E) hydrogen.

Answer 2

a phosphate group.

Question 3

The phenomenon of complementary base pairing is based on

A) the alternation of sugar-phosphate groups.
B) the relative sizes of purines and pyrimidines.
C) evolutionary relationships.
D) the differences found in RNA and DNA.
E) All of the above

Answer 3

B

Question 4

The four nitrogenous bases of RNA are abbreviated as

A) A,G,C,and T.
B) A,G,T,and N.
C) G,C,U,and N.
D) A,G,U,and T.
E) A,G,C,and U.

Question 5

A nucleotide consists of a pentose sugar,a phosphate group,and a(n)

A) lipid.
B) acid.
C) nitrogen-containing base.
D) amino acid.
E) glycerol.

Question 6

What is the difference between nucleosides and nucleotides?

A) Only nucleotides have nitrogenous bases.
B) Only nucleotides contain a phosphate group.
C) Nucleotides have the pentose sugar ribose,whereas nucleosides have the pentose sugar deoxyribose.
D) In nucleosides the monomers are joined by phosphodiester bonds;in nucleotides the monomers are joined by hydrogen bonds.
E) Nucleosides are the monomers of DNA,whereas nucleotides are the monomers of RNA.

Question 7

Which statement about purines and pyrimidines is true?

A) Purines include the bases of cytosine and thymine;pyrimidines include the bases of adenine and guanine.
B) Pyrimidines are found in RNA,whereas purines are found in DNA.
C) Purines consist of hydrogen,carbon,oxygen,and nitrogen,whereas pyrimidines have phosphorus,hydrogen,carbon,oxygen,and nitrogen.
D) Purines have only single bonds in their structure,whereas pyrimidines have both single and double bonds.
E) Purines are double-ring structures,whereas pyrimidines are single-ring structures.

Question 8

A nucleotide in DNA is made up of

A) four bases.
B) a base plus a ribose sugar.
C) a base plus a deoxyribose sugar plus phosphate.
D) a sugar plus a phosphate.
E) a sugar and a base.

Question 9

Nucleotides in RNA are connected to one another in the polynucleotide chain by

A) covalent bonds between bases.
B) covalent bonds between sugars.
C) covalent bonds between sugar and phosphate.
D) hydrogen bonds between purines.
E) hydrogen bonds between any bases.

Question 10

Which base is not found in DNA?

A) Thymine
B) Adenine
C) Uracil
D) Guanine
E) Cytosine

Question 11

The sides of the "ladder" that makes up a nucleic acid molecule are made of

A) nitrogenous bases.
B) pentose sugars and phosphate groups.
C) purines.
D) pyrimidines.
E) nucleosides.

Question 12

The nucleotide sequence of DNA

A) is the same in all organisms of a species.
B) contains only information for translation.
C) evolved before RNA.
D) contains the four bases A,T,G,and C.
E) All of the above

Question 13

Which statement about the differences between DNA and RNA is false?

A) DNA has thymine,whereas RNA has uracil.
B) DNA usually has two polynucleotide strands,whereas RNA usually has one strand.
C) DNA has deoxyribose sugar,whereas RNA has ribose sugar.
D) DNA is a polymer,whereas RNA is a monomer.
E) In DNA,A pairs with T,whereas in RNA,A pairs with U.

Question 14

Ribose and deoxyribose are both found in nucleic acids.One difference between ribose and deoxyribose is that

A) deoxyribose has one less oxygen molecule than ribose.
B) ribose has one less oxygen molecule than deoxyribose.
C) ribose is a pentose sugar,whereas deoxyribose is a hexose sugar.
D) deoxyribose is found in RNA,whereas ribose is found in DNA.
E) ribose binds a phosphate at the 3' position,whereas deoxyribose binds a phosphate at the 2'position.

Question 15

RNA differs from DNA in that RNA

A) contains uracil instead of thymine.
B) is single-stranded,whereas DNA is double-stranded.
C) is an intermediate in information transfer,whereas DNA encodes hereditary information.
D) contains ribose,whereas DNA contains deoxyribose.
E) All of the above

Question 16

Two complementary nucleotides are connected by _______ bonds.

A) hydrogen
B) ionic
C) peptide
D) phosphodiester
E) covalent

Question 17

In DNA,A pairs with T,and C pairs with G;these are examples of a specific type of reaction called

A) complementary base pairing.
B) a dehydration reaction.
C) a reduction reaction.
D) a hydrophobic reaction.
E) a purine-purine reaction.

Question 18

Single-stranded RNA can fold in on itself,creating three-dimensional structures for the bonding and recognition of other molecules.The folds are stabilized by _______ bonds.

A) hydrogen
B) ionic
C) phosphodiester
D) peptide
E) glycosidic

Question 19

Which statement about DNA and RNA is true?

A) DNA is single-stranded and RNA is double-stranded.
B) DNA is only informational and RNA is only catalytic.
C) DNA contains deoxyribose and RNA contains ribose.
D) DNA is transcribed and RNA is replicated.
E) DNA contains uracil (U)and RNA contains thymine (T).

Question 20

Both DNA and RNA include

A) pentoses.
B) hexoses.
C) fructoses.
D) maltoses.
E) amyloses.

Question 21

A macromolecule isolated from the bone of dinosaurs is found to have primary chains of nitrogen-carbon-carbon repeats.It would be classified as what type of molecule?

A) Polysaccharide
B) Oligosaccharide
C) Polypeptide
D) Triglyceride
E) Lipid

Question 22

A protein can best be defined as a polymer

A) of amino acids.
B) containing one or more polypeptide chains.
C) containing 20 amino acids.
D) containing 20 peptide linkages.
E) containing double helices.

Question 23

What is the nucleotide sequence of the complementary strand of the DNA molecule 5'-AATGCGA-3'?

A) 3'-CCGTTAT-5'
B) 3'-AATGCGA-5'
C) 3'-GGCATAG-5'
D) 3'-TTACGCT-5'
E) 5F'-AGCGTAA-3'

Question 24

Cytosine is a pyrimidine that forms three hydrogen bonds.Uracil is also a pyrimidine.Based on this information,one can conclude that uracil forms _______ hydrogen bonds and pairs with _______.

A) three;guanine (a two-bond pyrimidine)
B) three;adenine (a three-bond purine)
C) three;guanine (a three-bond purine)
D) two;adenine (a two-bond purine)
E) two;thymine (a two-bond pyrimidine)

Question 25

When an egg is exposed to extreme heat it turns from a liquid substance into a solid substance.Even when the egg is allowed to cool,these changes are not reversible for a number of reasons.Which is not one of those reasons?

A) Water has been removed from the egg proteins.
B) Rapidly moving molecules have broken apart hydrogen bonds and hydrophobic interactions in the egg's proteins.
C) Proteins in the egg have become denatured and lost secondary and tertiary structure.
D) The denatured proteins have aggregated.
E) Fats in the egg have become saturated and less fluid.

Question 26

Consider the following double-stranded DNA region: 5'-TGCCAT-3'
3'-ACGGTA-5'
If the lower strand is transcribed,which strand will result?

A) 3'-TGCCAT-5'
B) 5'-TCGGTA-3'
C) 5'-UGCCAU-3'
D) 3'-UGCCUA-5'
E) 5'-TCGGUT-3'

Question 27

If pyrimidines could bind to other pyrimidines,and purines could bind to other purines,what would be the impact on the DNA double helix?

A) The width of the double helix would vary rather than having a fixed width.
B) The phosphodiester bonds would be unable to form.
C) There would be a reduced requirement for phosphates in nucleotides.
D) The DNA backbone would be made of nucleosides.
E) The sugar would need to be ribose instead of deoxyribose.

Question 28

DNA molecules can differ from one another in their

A) physical shape.
B) function.
C) base sequences.
D) hydrogen bonds.
E) complementary base pairing.

Question 29

Amino acids can be classified by the

A) number of monosaccharides they contain.
B) number of carbon-carbon double bonds in their fatty acids.
C) number of peptide bonds they can form.
D) number of disulfide bridges they can form.
E) characteristics of their side chains.

Question 30

The magnesium chelatase protein has quaternary structure.This means that magnesium chelatase

A) is composed of multiple subunits.
B) binds to the surface of membranes.
C) forms part of a quadruple complex.
D) changes over time.
E) has four-fold symmetry.

Question 31

Which statement about proteins is true?

A) They are insoluble in water.
B) They are the structural units of glycogen.
C) They possess glycosidic linkages between amino acids.
D) Many function as enzymes.
E) They are involved in information storage.

Question 32

Almost all enzymes are

A) DNA.
B) lipids.
C) carbohydrates.
D) proteins.
E) amino acids.

Question 33

Which of the following depend(s)on complementary base pairing?

A) DNA replication
B) Transcription
C) Translation
D) Folding of an RNA molecule back on itself
E) All of the above

Question 34

What accounts for the stability of the double-stranded DNA molecule?

A) The hydrogen bonds between purines and pyrimidines
B) Phosphodiester bonds between the nitrogenous bases
C) Strong hydrogen bonds between the sugar and phosphate groups
D) Its double-helix shape
E) The direct bonding of the base to the phosphate molecule

Question 35

Which solution is least likely to denature an enzyme?

A) Urea
B) Acetic acid
C) Distilled water
D) Boiling water
E) Mercaptoethanol

Question 36

All of the following contribute to the overall structure of proteins except

A) charge differences between R groups.
B) disulfide bond formation between glycines.
C) interactions between R groups and the environment.
D) the N-H from the peptide backbone.
E) the C=O groups from the peptide backbone.

Question 37

If all of the cysteine residues of a protein were changed to threonines,what would happen to the protein structure?

A) Nothing would change because both residues have hydrophobic properties.
B) The structure would remain the same but the protein would lose activity.
C) The primary structure would be compromised because the protein would lose peptide bond formation.
D) The tertiary structure of the protein would be affected because it would lose disulfide bond formation.
E) The hydrogen bonds would be lost,affecting alpha and beta sheet formation.

Question 38

The double-helix structure of DNA is the overall result of

A) covalent base pairings.
B) the covalent bonding of purines and pyrimidines.
C) the phosphodiester bonds between deoxyribose and phosphate.
D) hydrogen bonding of the two complementary polynucleotide strands.
E) ionic bonding of base pairs.

Question 39

DNA carries genetic information in its

A) helical form.
B) sequence of bases.
C) tertiary sequence.
D) sequence of amino acids.
E) phosphate groups.

Question 40

If there is an exposed purine during DNA replication,what will be joined to it?

A) Any purine
B) One specific purine
C) One specific pyrimidine
D) Any pyramidine
E) A phosphate group

Question 41

Leucine and valine have side chains consisting entirely of C and H;therefore,the side chains

A) are hydrophilic.
B) are nonpolar.
C) contain sulfur atoms.
D) are electrically charged.
E) form only left-hand isomers.

Question 42

How many different types of tetrapeptides (molecules with four linked amino acids)can be made from the 20 common amino acids?

A) 4
B) 80
C) 256
D) 8,000
E) 160,000

Question 43

Which protein structure is not destroyed by denaturation?

A) Primary
B) Secondary
C) Tertiary
D) Quaternary
E) Both a and b

Question 44

The tertiary structure of a protein is determined by its

A) interactions among R groups.
B) right-handed coil.
C) hydrogen bonding.
D) branching.
E) glycosidic linkages.

Question 45

Peptide chains have a(n)_______ and a(n)_______.

A) start end;stop end
B) positive end;negative end
C) N terminus;C terminus
D) 5ʹ end;3ʹ end
E) A end;Z end

Question 46

What type of amino acid side chains would you expect to find on the surface of a protein embedded in the lipid-rich environment of a cell membrane?

A) Acidic
B) Hydrophobic
C) Hydrophilic
D) Charged
E) Polar,but not charged

Question 47

Which amino acid is small enough to fit into the tight corners of a protein molecule?

A) Proline
B) Glycine
C) Cysteine
D) Asparagine
E) Glutamine

Question 48

The amino acids of the protein keratin are arranged in an $\alpha$ helix.This secondary structure is stabilized by

A) covalent bonds.
B) peptide bonds.
C) glycosidic linkages.
D) polar bonds.
E) hydrogen bonds.

Question 49

Which interaction does not determine tertiary structure?

A) Hydrogen bond
B) Disulfide bridge
C) Glycosidic linkage
D) van der Waals interaction
E) Ionic bond

Question 50

The shape of a folded protein is determined by

A) its tertiary structure.
B) the sequence of its amino acids.
C) whether the peptide bonds have $\alpha$ or $\beta$ linkages.
D) the number of peptide bonds.
E) the base-pairing rules.

Question 51

The side chain of leucine is a hydrocarbon.In a folded protein,leucine would likely not be found

A) in the interior of a cytoplasmic enzyme.
B) on the exterior of a protein embedded in a membrane.
C) on the exterior of a cytoplasmic enzyme.
D) in the interior of a protein embedded in a membrane.
E) Both a and c

Question 52

Theoretically,the number of different proteins that can be made from 50 amino acids is

A) 50²⁰.
B) 20 × 50.
C) 20⁵⁰.
D) 10⁵⁰.
E) 2⁵⁰.

Question 53

Which amino acid has a sulfur atom?

A) Proline
B) Arginine
C) Methionine
D) Alanine
E) Glutamine

Question 54

The amino acid lysine

A) is found in all proteins.
B) has a negatively charged side chain.
C) has a hydrophobic side chain.
D) has a hydrophilic side chain.
E) is identical to the amino acid leucine.

Question 55

All proteins

A) are enzymes.
B) consist of one or more polypeptide chains.
C) consist of three amino acids.
D) have quaternary structures.
E) are more soluble in nonpolar solvents than in water.

Question 56

Which statement about the primary structure of a protein is false?

A) It may be branched.
B) It is held together by covalent bonds.
C) It is unique to that protein.
D) It determines the tertiary structure of the protein.
E) It is the sequence of amino acids in the protein.

Question 57

Aspartate and glutamate have side chains terminating in carboxyl groups;therefore,they

A) are hydrophobic.
B) have sulfur atoms in their side chains.
C) have electrically charged side chains.
D) are nonpolar.
E) form only left-hand isomers.

Question 58

A $\beta$ pleated sheet organization in a polypeptide chain is an example of _______ structure.

A) primary
B) secondary
C) tertiary
D) quaternary
E) coiled

Question 59

Amino acids can be grouped according to the properties of their

A) amino groups.
B) hydrogen.
C) carboxyl groups.
D) R groups.
E) $\alpha$ carbon.

Question 60

A(n)_______ protein is a protein that has become nonfunctional due to the loss of its three-dimensional structure.

A) permanent
B) reversible
C) denatured
D) hydrolyzed
E) environmentalized

Question 61

Quaternary structure is found in all proteins that

A) are composed of multiple subunits.
B) insert themselves into membranes.
C) are members of the quadruple complex.
D) change over time.
E) are enzymes.

Question 62

The rate of a chemical reaction in a cell is the measure of how

A) often the reaction occurs.
B) quickly the substrates are converted to product.
C) much energy must be added for the reaction to occur.
D) much activation energy is required for the reaction to occur.
E) easily the reaction is inhibited.

Question 63

Which statement about enzymes is false?

A) An enzyme changes shape when it binds to a substrate.
B) Enzymes lower the activation energy.
C) Enzymes are highly specific.
D) An enzyme may orient substrates,induce strain,or temporarily add chemical groups.
E) Most enzymes are much smaller than their substrates.

Question 64

The hydrolysis of sucrose to glucose and fructose is exergonic.However,if sucrose is dissolved in water and the solution is kept overnight at room temperature,there is no detectable conversion to glucose and fructose.Why?

A) The change in free energy of the reaction is positive.
B) The activation energy of the reaction is high.
C) The change in free energy of the reaction is negative.
D) This is a condensation reaction.
E) The free energy of the products is higher than the free energy of the reactants.

Question 65

The active site of an enzyme

A) never changes shape.
B) forms no chemical bonds with substrates.
C) determines,by its structure,the specificity of the enzyme.
D) looks like a lump projecting from the surface of the enzyme.
E) changes the $\Delta$ G of the reaction.

Question 66

In a chemical reaction,transition-state species have free energies that are

A) lower than either the reactants or the products.
B) higher than either the reactants or the products.
C) lower than the reactants,but higher than the products.
D) higher than the reactants,but lower than the products.
E) lower than the reactants,but the same as the products.

Question 67

The quaternary structure of a protein

A) consists of exactly four subunits-hence the name quaternary.
B) is unrelated to the function of the protein.
C) cannot change.
D) is determined mostly by covalent bonds.
E) depends on the primary structures of the subunits.

Question 68

Which statement about enzymes is true?

A) Enzymes are proteins.
B) Enzymes have a specific amino acid sequence.
C) Enzymes are highly specific.
D) Enzymes lower the energy barrier of a reaction.
E) All of the above

Question 69

An RNA molecule that has enzyme activity is called

A) RNAse.
B) ribonuclease.
C) an allosteric enzyme.
D) a regulatory enzyme.
E) a ribozyme.

Question 70

The molecules that are acted on by an enzyme are called

A) products.
B) substrates.
C) carriers.
D) prosthetics.
E) effectors.

Question 71

In some cases,a substrate-enzyme complex is stabilized by

A) hydrogen bonds.
B) covalent bonds.
C) ionic attractions.
D) hydrophobic interactions.
E) All of the above

Question 72

Trypsin and elastase are both enzymes that catalyze hydrolysis of peptide bonds.But trypsin only cuts next to lysine and elastase only cuts next to alanine.Why?

A) Trypsin is a protein,and elastase is not.
B) $\Delta$ G for the two reactions is different.
C) The shape of the active site for the two enzymes is different.
D) One of the reactions is endergonic and the other is exergonic.
E) Hydrolysis of lysine bonds requires water,whereas hydrolysis of alanine bonds does not.

Question 73

A reactant reaches the transition state

A) right before the energy barrier is overcome.
B) when it is ready to receive energy.
C) after releasing free energy.
D) when there is an input of energy to initiate the reaction.
E) only when enzymes are used.

Question 74

An active site is

A) the part of the substrate that binds with an enzyme.
B) the part of the enzyme that binds with a substrate.
C) the site where energy is added to an enzyme catalyst.
D) the site where enzymes are found in cells.
E) important in determining secondary structure.

Question 75

Which statement about enzymes is false?

A) They usually consist of proteins.
B) They change the rate of the catalyzed reaction.
C) They change the $\Delta$ G of the reaction.
D) They are sensitive to heat.
E) They are sensitive to pH.

Question 76

The enzyme sucrase increases the rate at which sucrose is broken down into glucose and fructose.Sucrase works by

A) increasing the amount of free energy of the reaction.
B) lowering the activation energy of the reaction.
C) decreasing the equilibrium constant of the reaction.
D) supplying energy to speed up the reaction.
E) changing the shape of the active site.

Question 77

Knowing the change in free energy ( $\Delta$ G)of a reaction tells us

A) the energy yield of the reaction.
B) the rate of the reaction.
C) the end concentration of products.
D) the optimum temperature for the reaction.
E) the activation energy.

Question 78

The binding of substrate to enzyme creates a(n)

A) transition state.
B) activation groove.
C) catalyst.
D) enzyme-substrate complex.
E) energy barrier.

Question 79

Ribozymes are

A) enzymes that are made up of ribose sugar.
B) ancient catalysts that no longer exist.
C) RNA catalysts.
D) present in bacterial cells only.
E) less active than protein enzymes.

Question 80

Which factor determines the rate of a reaction?

A) Entropy
B) $\Delta$ G
C) The laws of thermodynamics
D) The activation energy
E) The overall change in free energy