Question 1

Which of the following is a feature of allosteric regulation of enzyme activity?

Accepted Answer

A)  Ligand binding causes a conformation change in the enzyme. 
B)  Allosteric enzymes often have multiple active sites. 
C)  Cooperativity in substrate binding. 
D)  There is often a range of different effectors for a single enzyme. 
E)  All of the above 
A)  Ligand binding causes a conformation change in the enzyme. 
B)  Allosteric enzymes often have multiple active sites. 
C)  Cooperativity in substrate binding. 
D)  There is often a range of different effectors for a single enzyme. 
E)  All of the above

Question 2

A common feature of serine proteases is the catalytic triad consisting of a nucleophile, a general base and an acid. In chymotrypsin these amino acid residues are ________, ________, and ________ respectively.

Accepted Answer

serine, hi

Question 3

Almost all irreversible enzyme inhibitors bind noncovalently to the enzyme.

Accepted Answer

A) True 
 B)False

Question 4

A Lineweaver-Burk plot can be used to determine KM using initial-rate data for an enzyme-catalyzed reaction.

Accepted Answer

A) True 
 B)False

Question 5

Enzymes can accelerate reactions by:

Accepted Answer

A)  binding a substrate or substrates. 
B)  promoting the removal or addition of protons. 
C)  correctly positioning a metal ion for catalysis. 
D)  lowering the energy for activation. 
E)  all of the above. 
A)  binding a substrate or substrates. 
B)  promoting the removal or addition of protons. 
C)  correctly positioning a metal ion for catalysis. 
D)  lowering the energy for activation. 
E)  all of the above.

Question 6

Coenzymes or cofactors are irreversibly changed during catalysis.

Accepted Answer

A) True 
 B)False

Question 7

Feedback regulation of a metabolic pathway can either be activation or inhibition.

Accepted Answer

A) True 
 B)False

Question 8

Catalytically inactive enzyme precursors are called ________.

Accepted Answer

The answer of Catalytically inactive enzyme precursors are called ________....

Question 9

In a favorable reaction the free energy of the products is ________ than the free energy of the reactants.

Accepted Answer

The answer of In a favorable reaction the free energy...

Question 10

Which of the following statements applies to metalloenzymes?

Accepted Answer

A)  Some metal ions assist in ATP binding. 
B)  Amino acid residues in the enzyme are never covalently linked to the metal ion. 
C)  The metal does not bind at the catalytic site. 
D)  Many are oxido-reductases. 
E)  A and D 
A)  Some metal ions assist in ATP binding. 
B)  Amino acid residues in the enzyme are never covalently linked to the metal ion. 
C)  The metal does not bind at the catalytic site. 
D)  Many are oxido-reductases. 
E)  A and D

Question 11

A stopped-flow apparatus is used to measure rates of pre-steady state slow enzymatic reactions.

Accepted Answer

A) True 
 B)False

Question 12

The cofactor NAD+ is:

Accepted Answer

A)  a reductant. 
B)  an oxidant. 
C)  oxidized to NADH/H+ in dehydrogenase reactions. 
D)  able to accept 2 electrons and 2 protons. 
E)  covalently linked to enzymes in whose catalytic activity it assists. 
A)  a reductant. 
B)  an oxidant. 
C)  oxidized to NADH/H+ in dehydrogenase reactions. 
D)  able to accept 2 electrons and 2 protons. 
E)  covalently linked to enzymes in whose catalytic activity it assists.

Question 13

Random substrate binding, ordered substrate binding and the ping-pong mechanism are all features of ________ enzyme-catalyzed reactions.

Accepted Answer

The answer of Random substrate binding, ordered substrate binding and...

Question 14

Which of the following statement is FALSE?

Accepted Answer

A)  The free energy barrier in a chemical reaction must be overcome in order for products to form. 
B)  An increase in temperature can result in an increased reaction rate. 
C)  Lowering the free energy of the transition state can increase a reaction rate. 
D)  At a given temperature and time all molecules in a solution or a sample will have the same energy. 
E)  An enzyme can increase a reaction rate by lowering the activation energy. 
A)  The free energy barrier in a chemical reaction must be overcome in order for products to form. 
B)  An increase in temperature can result in an increased reaction rate. 
C)  Lowering the free energy of the transition state can increase a reaction rate. 
D)  At a given temperature and time all molecules in a solution or a sample will have the same energy. 
E)  An enzyme can increase a reaction rate by lowering the activation energy.

Question 15

Which of the following is NOT a feature of substrate-level enzyme regulation?

Accepted Answer

A)  A high substrate concentration will speed up the rate of reaction. 
B)  A high product concentration will slow the rate of reaction. 
C)  The product can be a competitor. 
D)  It is sufficient for regulation of most enzyme-catalyzed reactions. 
E)  Sometimes products can be competitive or uncompetitive. 
A)  A high substrate concentration will speed up the rate of reaction. 
B)  A high product concentration will slow the rate of reaction. 
C)  The product can be a competitor. 
D)  It is sufficient for regulation of most enzyme-catalyzed reactions. 
E)  Sometimes products can be competitive or uncompetitive.

Question 16

The formation of an enzyme-substrate complex tends to be thermodynamically favorable due to ________ interactions between the substrate and enzyme.

Accepted Answer

The answer of The formation of an enzyme-substrate complex tends...

Question 17

A mutation causing an amino acid change in an enzyme that affects the turnover number kcat will always affect the KM as well.

Accepted Answer

A) True 
 B)False

Question 18

A reversible ________ inhibitor is one that binds to the active site of an enzyme but cannot undergo the chemical conversion step of the reaction.

Accepted Answer

The answer of A reversible ________ inhibitor is one that...

Question 19

A ribonucleic acid that can act as a biological catalyst is called a ________.

Accepted Answer

The answer of A ribonucleic acid that can act as...

Question 20

Non-catalyzed biochemical reactions always occur at physiological useful timescales.

Accepted Answer

A) True 
 B)False

Exam 8: Enzymes: Biological Catalysts

Which of the following is a feature of allosteric regulation of enzyme activity?

A common feature of serine proteases is the catalytic triad consisting of a nucleophile, a general base and an acid. In chymotrypsin these amino acid residues are ________, ________, and ________ respectively.

Almost all irreversible enzyme inhibitors bind noncovalently to the enzyme.

A Lineweaver-Burk plot can be used to determine KM using initial-rate data for an enzyme-catalyzed reaction.

Enzymes can accelerate reactions by:

Coenzymes or cofactors are irreversibly changed during catalysis.

Feedback regulation of a metabolic pathway can either be activation or inhibition.

Catalytically inactive enzyme precursors are called ________.

In a favorable reaction the free energy of the products is ________ than the free energy of the reactants.

Which of the following statements applies to metalloenzymes?

A stopped-flow apparatus is used to measure rates of pre-steady state slow enzymatic reactions.

The cofactor NAD+ is:

Random substrate binding, ordered substrate binding and the ping-pong mechanism are all features of ________ enzyme-catalyzed reactions.

Which of the following statement is FALSE?

Which of the following is NOT a feature of substrate-level enzyme regulation?

The formation of an enzyme-substrate complex tends to be thermodynamically favorable due to ________ interactions between the substrate and enzyme.

A mutation causing an amino acid change in an enzyme that affects the turnover number kcat will always affect the KM as well.

A reversible ________ inhibitor is one that binds to the active site of an enzyme but cannot undergo the chemical conversion step of the reaction.

A ribonucleic acid that can act as a biological catalyst is called a ________.

Non-catalyzed biochemical reactions always occur at physiological useful timescales.

Biochemistry and the Language of Chemistry

The Chemical Foundation of Life: Weak Interactions in an Aqueous Environment

The Energetics of Life

Nucleic Acids

Introduction to Proteins: the Primary Level of Protein Structure

The Three-Dimensional Structure of Proteins

Protein Function and Evolution

Carbohydrates: Sugars, Saccharides, Glycans

Lipids, Membranes, and Cellular Transport

Chemical Logic of Metabolism

Carbohydrate Metabolism: Glycolysis, Gluconeogenesis, Glycogen Metabolism, and the Pentose Phosphate Pathway

The Citric Acid Cycle

Electron Transport, Oxidative Phosphorylation, and Oxygen Metabolism

Photosynthesis

Lipid Metabolism

Interorgan and Intracellular Coordination of Energy Metabolism in Vertebrates

Amino Acid and Nitrogen Metabolism

Nucleotide Metabolism

Mechanisms of Signal Transduction

Genes, Genomes, and Chromosomes

DNA Replication

DNA Repair, Recombination, and Rearrangement

Transcription and Post-Transcriptional Processing

Information Decoding: Translation and Post-Translational Protein Processing

Regulation of Gene Expression

Filters

A common feature of serine proteases is the catalytic triad consisting of a nucleophile, a general base and an acid. In chymotrypsin these amino acid residues are , , and respectively.