Question 1

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

Accepted Answer

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. 
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 2

The four nitrogenous bases of RNA are abbreviated as

Accepted Answer

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. 
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 3

All proteins

Accepted Answer

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. 
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 4

Which statement about enzymes is false?

Accepted Answer

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. 
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 5

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

Accepted Answer

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

Question 6

RNA differs from DNA in that RNA

Accepted Answer

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 
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 7

An experiment is carried out in which a small amount of allosteric inhibitor is added to tube A and no inhibitor is added to tube B.The full reaction is completed in Tube B twice as fast as in tube A.One can conclude that the allosteric inhibitor acted by

Accepted Answer

A)  decreasing the number of enzyme molecules. 
B)  increasing the amount of the active form of the enzyme. 
C)  decreasing the amount of the inactive form of the enzyme. 
D)  decreasing the amount of the active form of the enzyme. 
E)  increasing the amount of substrate. 
A)  decreasing the number of enzyme molecules. 
B)  increasing the amount of the active form of the enzyme. 
C)  decreasing the amount of the inactive form of the enzyme. 
D)  decreasing the amount of the active form of the enzyme. 
E)  increasing the amount of substrate.

Question 8

Enzymes are highly sensitive to pH and temperature because

Accepted Answer

A)  changes in the environment raise their activation energy. 
B)  changes in temperature and pH readily break their hydrogen bonds and can alter the enzyme shape. 
C)  environmental changes affect their primary structure. 
D)  at extreme temperatures and pH levels,coenzymes add chemical groups to the substrate. 
E)  extremes of temperature and pH level change the ionization rate. 
A)  changes in the environment raise their activation energy. 
B)  changes in temperature and pH readily break their hydrogen bonds and can alter the enzyme shape. 
C)  environmental changes affect their primary structure. 
D)  at extreme temperatures and pH levels,coenzymes add chemical groups to the substrate. 
E)  extremes of temperature and pH level change the ionization rate.

Question 9

Which statement about proteins is true?

Accepted Answer

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. 
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 10

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?

Accepted Answer

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

Question 11

If the temperature of an enzyme-catalyzed reaction is increased from 40°C to 70°C,the rate of the reaction

Accepted Answer

A)  will increase indefinitely. 
B)  will decrease immediately. 
C)  will decrease to zero because the enzyme denatures. 
D)  will decrease and then increase. 
E)  cannot be determined without information regarding optimal temperature. 
A)  will increase indefinitely. 
B)  will decrease immediately. 
C)  will decrease to zero because the enzyme denatures. 
D)  will decrease and then increase. 
E)  cannot be determined without information regarding optimal temperature.

Question 12

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

Accepted Answer

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. 
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 13

An RNA molecule that has enzyme activity is called

Accepted Answer

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

Question 14

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?

Accepted Answer

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

Question 15

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

Accepted Answer

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. 
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 16

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

Accepted Answer

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

Question 17

With the addition of the enzyme alcohol dehydrogenase,the rate of reduction of acetaldehyde to ethanol increases as the concentration of acetaldehyde is increased.Eventually,the rate of the reaction reaches a maximum,at which point further increases in the concentration of acetaldehyde have no effect.Why?

Accepted Answer

A)  All the alcohol dehydrogenase molecules are bound to acetaldehyde molecules. 
B)  At high concentrations of acetaldehyde,the activation energy of the reaction increases. 
C)  At high concentrations of acetaldehyde,the activation energy of the reaction decreases. 
D)  The enzyme is no longer specific for acetaldehyde. 
E)  At high concentrations of acetaldehyde,the change in free energy of the reaction decreases. 
A)  All the alcohol dehydrogenase molecules are bound to acetaldehyde molecules. 
B)  At high concentrations of acetaldehyde,the activation energy of the reaction increases. 
C)  At high concentrations of acetaldehyde,the activation energy of the reaction decreases. 
D)  The enzyme is no longer specific for acetaldehyde. 
E)  At high concentrations of acetaldehyde,the change in free energy of the reaction decreases.

Question 18

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

Accepted Answer

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. 
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 19

Which statement about enzymes is false?

Accepted Answer

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. 
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 20

Quaternary structure is found in all proteins that

Accepted Answer

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. 
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.

Exam 3: Nucleic Acids, Proteins, and Enzymes

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

The four nitrogenous bases of RNA are abbreviated as

All proteins

Which statement about enzymes is false?

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

RNA differs from DNA in that RNA

An experiment is carried out in which a small amount of allosteric inhibitor is added to tube A and no inhibitor is added to tube B.The full reaction is completed in Tube B twice as fast as in tube A.One can conclude that the allosteric inhibitor acted by

Enzymes are highly sensitive to pH and temperature because

Which statement about proteins is true?

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?

If the temperature of an enzyme-catalyzed reaction is increased from 40°C to 70°C,the rate of the reaction

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

An RNA molecule that has enzyme activity is called

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?

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

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

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

Which statement about enzymes is false?

Quaternary structure is found in all proteins that

Introduction

The Chemistry and Energy of Life

Cells: the Working Units of Life

Cell Membranes and Signaling

Pathways That Harvest and Store Chemical Energy

The Cell Cycle and Cell Division

Inheritance, Genes, and Chromosomes

DNA and Its Role in Heredity

From Dna to Protein: Gene Expression

Regulation of Gene Expression

Genomes

Biotechnology

Genes, Development, and Evolution

Processes of Evolution

Reconstructing and Using Phylogenies

Speciation

The History of Life on Earth

Bacteria, Archaea, and Viruses

The Origin and Diversification of Eukaryotes

The Evolution of Plants

The Evolution and Diversity of Fungi

Animal Origins and Diversity

The Plant Body

Plant Nutrition and Transport

Plant Growth and Development

Reproduction of Flowering Plants

Plants in the Environment

Fundamentals of Animal Function

Nutrition and Digestion

Breathing

Circulation

Muscle and Movement

Neurons, Sense Organs, and Nervous Systems

Nervous and Endocrine Control

Water and Salts: Excretion

Animal Reproduction

Animal Development

Immunology: Animal Defense Systems

Animal Behavior

The Distribution of Earths Ecological Systems

Populations

Ecological and Evolutionary Consequences of Interactions Within and Among Species

Ecological Communities

The Global Ecosystem

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