Enzyme Inhibitor & Reaction Energy
These Biochemistry chapters discuss enzyme inhibitor, reactions in a cell & reaction energy.
Which of the following refers to the term metabolism?
a.all the reactions in a cell or organism – correct
b.all the reactions in a cell that break down molecules only
c.all the reactions in a cell that build new molecules only
d.all the reactions in a cell that decompose molecules only
Which of the following best describes an endergonic reaction?
a.absorbs energy from the environment – correct
b.is coupled with another reaction
c.is involved in biosynthesis
d.releases energy into the environment
Chemotrophs obtain their energy from which of the following?
a.inorganic chemical reactions only
b.light energy
c.organic chemical reactions only
d.organic and inorganic chemical reactions – correct
Which of the following describes a molecule that had an electron removed?
a.anabolized
b.electronated
c.oxidized – correct
d.reduced
Which of the following best describes the subcomponents of pyrophosphate?
a.two inorganic phosphate molecules- correct
b.two organic phosphate molecules
c.three inorganic phosphate molecules
d.three organic phosphate molecules
Which site on an enzyme is where substrates bind?
a.the activation site
b.the active site- correct
c.the catalyst site
d.the lock and key site
Which of the following best describes catabolic pathways?
a.They always absorb energy.
b.They break down large molecules into smaller components.- correct
c.They build up large molecules from smaller components.
d.They must be coupled with the breakdown of ATP
Which group comprises all lithotrophs?
a.algae
b.autotrophs
c.microbes – correct
d.plants
Which is a common electron acceptor in catabolic reactions?
a.ATP
b.FADH2
c.NAD+ – correct
d.NADPH
The reaction that breaks down ATP to form ADP and inorganic phosphate is classified as which of the following?
a.endergonic
b.exergonic – correct
c.nonspontaneous
d.reduction
Which of the following is an inhibitor that binds to the active site of an enzyme?
a.a competitive inhibitor – correct
b.a noncompetitive inhibitor
c.an allosteric inhibitor
d.an uncompetitive inhibitor
Glycolysis produces a net gain of which of the following?
a.two ATP, two NADH, and two pyruvates – correct
b.two ATP, two NADH, and four pyruvates
c.two ATP, four NADH, and two pyruvates
d.four ATP, two NADH, and two pyruvates
Which of the following is a pathway that breaks down glucose in some microbes?
a.the Calvin cycle
b.the Entner-Doudoroff pathway – correct
c.the Krebs cycle
d.the tricarboxylic acid cycle
Which of the following best describes a transition reaction?
a.a reaction that converts pyruvate to acetyl CoA with the release of carbon dioxide – correct
b.a series of reactions that convert citric acid to oxaloacetate
c.an optional reaction that transports pyruvate into the mitochondrion
d.the reaction that converts glucose to glucose-6-phosphate in glycolysis
Which of the following is not a product of the Krebs cycle?
a.carbon dioxide
b.GTP, which is converted to ATP
c.NADH
d.pyruvate – correct
The Krebs cycle begins with the addition of acetyl CoA to which of the following?
a.citric acid
b.oxaloacetate – correct
c.ribulose bisphosphate
d.succinate dehydrogenase
Which of the following is the step in which CO2 enters the light-independent reactions (Calvin cycle)?
a.fixation – correct
b.reduction
c.regeneration
d.transition
Carotenoids are pigments that are which of the following colors?
a.blue/green
b.green/orange
c.orange/yellow/red – correct
d.purple/blue
Which of the following are enzymes that break down proteins?
a.amylases
b.oxidasesc.
c.oxygenases
d.proteases – correct
Fatty acids are often degraded using which set of reactions
a.β-oxidation – correct
b.glycolysis
c.photophosphorylation
d.the tricarboxylic acid cycle
Triglycerides are broken down by which of the following?
a.lipases – correct
b.nitrogenases
c.phospholipases
d.proteases
During the Krebs cycle, FAD is reduced to which of the following
a.FADH
b.FADH2 – correct
c.NADH
d.NADH2
Which of the following is the purpose of fermentation?
a.to produce carbon dioxide
b.to produce large quantities of additional energy
c.to regenerate NAD+ – correct
d.to regenerate oxygen
ATP is produced through oxidative phosphorylation when which of the following occurs?
a.FADH2 donates electrons to succinate dehydrogenase
b.H+ moves through ATP synthase – correct
c.NADH donates electrons to NADH dehydrogenase
d.the light-independent reactions fix CO2
Which of the following are inorganic molecules that bind to enymes?
Cofactors – correct
A general term is applied to an inactive enzyme. An inactive enzyme that requires chemical modification before it becomes active is called a(n) .
Zymogen – correct
Suppose a sequence of enzymatically catalyzed reactions converts substrate A to final product D through a sequence of reactions involving the production of intermediate products B and C as shown. Product D inhibits enzyme E1.
If the enzymes E1-E3 are all present in a test tube and substrate A is added to the reaction mixture, how will the concentration of intermediate B change?
E1 E2 E3
A B C D
first increase, then decrease
When A is added, some B will be produced, so its concentration will rise. As D is produced and begins to inhibit E1, the rate of production of B will fall. Since E2 causes C to be produced from B, the concentration of B will then fall.
What’s a term for a regulator substrate that binds to the regulatory site of an enzyme and changes the conformation of the active site?
allosteric regulator – correct
An enzyme that transfers a phosphate moiety in a reaction is called a ___________. The most common source of phosphate for biochemical reactions is ___________.
Kinase, ATP
Which of the following refers to the term metabolism?
A. all the reactions in a cell or organism
B. all the reactions in a cell that break down molecules only
C. all the reactions in a cell that build new molecules only
D. all the reactions in a cell that decompose molecules only
Which of the following best describes an endergonic reaction?
A. absorbs energy from the environment
B. is coupled with another reaction
C. is involved in biosynthesis
D. releases energy into the environment
Chemotrophs obtain their energy from which of the following?
A. inorganic chemical reactions only
B. light energy
C. organic chemical reactions only
D. organic and inorganic chemical reactions
Which of the following describes a molecule that had an electron removed?
A. anabolized
B. electronated
C. oxidized
D. reduced
Which of the following best describes the subcomponents of pyrophosphate?
A. two inorganic phosphate molecules
B. two organic phosphate molecules
C. three inorganic phosphate molecules
D. three organic phosphate molecules
Which molecule is often called the cell’s energy currency?
A. adenosine triphosphate
B. flavin adenine dinucleotide
C. nicotinamide adenine dinucleotide
D. nicotinamide adenine dinucleotide phosphate
Which site on an enzyme is where substrates bind?
A. the activation site
B. the active site
C. the catalyst site
D. the lock and key site
Which of the following are inorganic molecules that bind to enzymes?
A. apoenzymes
B. coenzymes
C. cofactors
D. holoenzymes
Which of the following best describes catabolic pathways?
A. They always absorb energy.
B. They break down large molecules into smaller components.
C. They build up large molecules from smaller components.
D. They must be coupled with the breakdown of ATP.
Which group comprises all lithotrophs?
A. algae
B. autotrophs
C. microbes
D. plants
Which is a common electron acceptor in catabolic reactions?
A. ATP
B. FADH2
C. NAD+
D. NADPH
The reaction that breaks down ATP to form ADP and inorganic phosphate is classified as which of the following?
A. endergonic
B. exergonic
C. nonspontaneous
D. reduction
Which of the following is an inhibitor that binds to the active site of an enzyme?
A. a competitive inhibitor
B. a noncompetitive inhibitor
C. an allosteric inhibitor
D. an uncompetitive inhibitor
Glycolysis produces a net gain of which of the following?
A. two ATP, two NADH, and two pyruvates
B. two ATP, two NADH, and four pyruvates
C. two ATP, four NADH, and two pyruvates
D. four ATP, two NADH, and two pyruvates
Which of the following is a pathway that breaks down glucose in some microbes?
A. the Calvin cycle
B. the Entner-Doudoroff pathway
C. the Krebs cycle
D. the tricarboxylic acid cycle
Which of the following best describes a transition reaction?
A. a reaction that converts pyruvate to acetyl CoA with the release of carbon dioxide
B. a series of reactions that convert citric acid to oxaloacetate
C. an optional reaction that transports pyruvate into the mitochondrion
D. the reaction that converts glucose to glucose-6-phosphate in glycolysis
Which of the following is nota product of the Krebs cycle?
A. carbon dioxide
B. GTP, which is converted to ATP
C. NADH
D. pyruvate
The Krebs cycle begins with the addition of acetyl CoA to which of the following?
A. citric acid
B. oxaloacetate
C. ribulose bisphosphate
D. succinate dehydrogenase
During the Krebs cycle, FAD is reduced to which of the following?
A. FADH
B. FADH2
C. NADH
D. NADH2
Which of the following is the purpose of fermentation?
A. to produce carbon dioxide
B. to produce large quantities of additional energy
C. to regenerate NAD+
D. to regenerate oxygen
ATP is produced through oxidative phosphorylation when which of the following occurs?
A. FADH2 donates electrons to succinate dehydrogenase
B. H+ moves through ATP synthase
C. NADH donates electrons to NADH dehydrogenase
D. the light-independent reactions fix CO
Each pyruvate molecule contains how many carbon atoms?
A. two
B. three
C. four
D. six
When is the pentose phosphate pathway favored over other pathways to break down glucose?
A. when biosynthesis is not needed
B. when phospholipids are needed
D. when the cell has a severe energy deficit and needs energy rapidly
C. when the synthesis of nucleic acids and proteins is needed
Which of the following best defines chemiosmosis?
A. the disruption of the inner mitochondrial membrane, which dissipates energy
B. the movement of electrons from one acceptor to another
C. the movement of hydrogen ions through ATP synthase
D. the series of reactions that regenerate oxaloacetate
Why is the actual ATP yield of aerobic respiration often less than the maximum possible yield of 38 ATP?
A. Aerobic respiration competes with anaerobic respiration for energy.
B. Aerobic respiration competes with fermentation for energy.
C. In eukaryotes, energy is used to move molecules across membranes.
D. No organisms complete all parts of aerobic respiration.
Glycolysis cannot occur in an anaerobic environment.
False
Nitrogen is fixed to ammonia by cyanobacteria and other microbes.
True
Fermentation is necessary because it provides additional energy compared with glycolysis alone.
False
chemoautotroph
uses chemical energy and an inorganic carbon source
chemoheterotroph
uses chemical energy and an organic carbon source
photoautotroph
uses light energy and an inorganic carbon source
photoheterotroph
uses light energy and an organic carbon source
chemoautotroph
iron-oxidizing bacteria
chemoheterotroph
animals
photoautotroph
purple sulfur bacteria
photoheterotroph
green nonsulfur bacteria
apoenzyme
an inactive enzyme lacking its coenzyme or cofactor
Coenzyme
an organic enzyme helper molecule
Cofactor
an inorganic enzyme helper molecule
holoenzyme
an active enzyme with its coenzyme or cofactor
electron transport chain of cellular respiration
inner mitochondrial membrane
glycolysis
cytoplasm
Kreb Cycle
mitochondrial matrix
light-independent reactions (Calvin cycle)
stroma of chloroplast
light reactions of photosynthesis
thylakoid membrane
aerobic respiration
uses an electron transport chain with O2 as the terminal electron acceptor
Anaerobic respiration
uses an electron transport chain with an inorganic molecule such as SO42- as the terminal electron acceptor
Fermentation
regenerates NAD+ for glycolysis by donating an electron to an endogenous organic molecule, often pyruvate
Which of the following is the step in which CO2 enters the light-independent reactions (Calvin cycle)?
A. fixation
B. reduction
C. regeneration
D. transition
Carotenoids are pigments that are which of the following colors?
A. blue/green
B. green/orange
C. orange/yellow/red
D. purple/blue
Which of the following are enzymes that break down proteins?
A. amylases
B. oxidases
C. oxygenases
D. proteases
Fatty acids are often degraded using which set of reactions?
A. β-oxidation
B. glycolysis
C. photophosphorylation
D. the tricarboxylic acid cycle
Triglycerides are broken down by which of the following?
A. lipases
B. nitrogenases
C. phospholipases
D. proteases
Which of the following best defines chemiosmosis?
A. the disruption of the inner mitochondrial membrane, which dissipates energy
B. the movement of electrons from one acceptor to another
C. the movement of hydrogen ions through ATP synthase
D. the series of reactions that regenerate oxaloacetate
Which of the following is the most acidic location in a mitochondrion?
A. the intermembrane space
B. the matrix
C. within the outer membrane
D. within the thylakoid
Which of the following is not a common electron acceptor in anaerobic respiration?
A. Fe3
B. H2S
C. NO3-
D. PO43-
The light reactions of photosynthesis include an electron transport chain.
True
E. coli can be distinguished from some if its close gram-negative relatives because it can ferment lactose.
True
Oxygen is necessary for an electron transport chain to function.
False
alcohol
ethanol and CO2 only
butanediol
formic acid, lactic acid, and other products
mixed acid
succinic acid and other products
propionic acid
acetic acid and other products
A bacteriophage transfers DNA of the previous host to the current host. This is an example of
a. Conjugation
b. Generalized transduction
c. Specialized transduction
d. Creation of an Hfr cell
e. None of the choices are correct
A frameshift is caused by ______ mutations?
a. Missense and insertion
b. Missense and nonsense
c. Nonsense and deletion
d. Deletion and insertion
e. Insertion and nonsense
A nucleosome is a linear chromosome wound around the
a. Nuclear membrane
b. rRNA
c. mRNA
d. Histone
e. Nucleolus
A permanent, inheritable change in the genetic information is called a(n)
a. Translation
b. Transcription
c. Mutation
d. Alteration
e. Regeneration
A primer of ____ is needed at the origin of nucleotide addition.
a. Polymerase III
b. Polymerase I
c. Helicase
d. RNA
e. DNA
A sequence of bases on a gene that does not code for protein is called a/an
a. Promoter
b. Operator
c. Operon
d. Exon
e. Intron
All of the following pertain to transcription except
a. Occurs on a ribosome in the cytoplasm
b. Occurs before translation
c. Requires RNA polymerase
d. Requires a template DNA strand
e. Is a process of protein synthesis
Among the microorganisms, various genomes can include
a. Chromosomes
b. Plasmids
c. Mitochondrial DNA
d. Chloroplast DNA
e. All of the choices are correct
Bacterial conjugation involves
a. Bacteriophage carrying donor DNA to the recipient cell
b. A donor cell with a plasmid that synthesizes a pilus
c. Naked DNA fragments from a lysed donor cell are taken up by a recipient cell
d. New progeny cells with genes from two parent bacterial cells
e. None of the choices are correct
Base pairs in DNA are held together by _____ bonds.
a. Peptide
b. Non polar covalent
c. Polar covalent
d. Hydrogen
e. Sulfhydryl
DNA Polymerase I
a. Removes primers
b. Adds bases to new DNA chain
c. Seals DNA gaps
d. Proofreads DNA chain
e. All of the choices are correct
DNA polymerase III
a. Is needed for adding nucleotides during mRNA synthesis
b. Synthesizes new DNA only in the 5′ to 3′ direction
c. Cannot add nucleotides to the lagging strand
d. Synthesizes an RNA primer
e. All of the choices are correct
Each nucleotide is composed of
a. One phosphate, one nitrogenous base, one sugar
b. One phosphate, one nitrogenous base, two sugars
c. Two phosphates, one nitrogenous base, one sugar
d. Two phosphates, one nitrogenous base, two sugars
e. One phosphate, two nitrogenous bases, one sugar
Eukaryotic chromosomes differ from prokaryotic chromosomes because only eukaryotes have
a. Histone proteins
b. Chromosomes in a nucleus
c. Several to many chromosomes
d. Elongated, not circular, chromosomes
e. All of the choices are correct
Gene regulation can involve a protein repressor that blocks _____ from initiating transcription.
a. DNA polymerase I
b. DNA polymerase III
c. RNA polymerase
d. mRNA
e. rRNA
Groups of three consecutive bases along the DNA of a gene have the code for one
a. Protein
b. Nucleotide
c. Amino acid
d. Purine
e. None of the choices are correct
Helicase
a. Unwinds DNA
b. Supercoils DNA
c. Unwinds RNA
d. Winds RNA
e. None of the choices are correct
If the wild type DNA sequence reads THE CAT ATE THE BIG RAT, what type of mutation would change the sequence to THE CAT ATA ETH EBI GRA T?
a. Missense
b. Nonsense
c. Insertion
d. Deletion
e. Silent
If the wild type DNA sequence reads THE CAT ATE THE BIG RAT, what type of mutation would change the sequence to THE CAT ATE (stop)?
a. Missense
b. Nonsense
c. Insertion
d. Deletion
e. Silent
If you have the sequence of mRNA that is AUAUGC, then the DNA antisense strand is ____.
a. AUAUGC
b. UAUACG
c. TATACG
d. CGUAUA
RNA molecules differ from DNA molecules because only RNA
a. Has ribose
b. Has uracil
c. Is typically one strand of nucleotides
d. Does not have thymine
e. All of the choices are correct
RNA polymerase binds to the
a. Start codon
b. Termination sequence
c. Regulation sequence
d. Promoter sequence
e. None of the choices are correct
Semiconservative replication refers to
a. Each base bonding at the 1′ position of the sugar
b. A purine always bonding to a pyrimidine
c. One helix strand that runs from the 5′ to 3′ direction and the other strand runs from the 3′ to 5′ direction
d. An original parent DNA strand and one newly synthesized DNA strand comprising a new DNA molecule
e. None of the choices are correct
The DNA of microorganisms is made up of subunits called
a. Histones
b. Amino acids
c. Nucleotides
d. mRNA
e. Polymerases
The RNA molecules that carry amino acids to the ribosomes during protein synthesis are called
a. Ribosomal RNA
b. Messenger RNA
c. Transfer RNA
d. Primer RNA
e. Ribozymes
The _____ is all of the genetic material of a cell.
a. Chromosome
b. Plasmid
c. Prophage
d. Genome
e. Proteome
The antiparallel arrangement within DNA molecules refers to
a. Each base bonding at the 1′ position of the sugar
b. A purine always bonding to a pyrimidine
c. One helix strand that runs from the 5′ to 3′ direction and the other strand runs from the 3′ to 5′ direction
d. An original parent DNA strand and one newly synthesized DNA strand comprising a new DNA molecule
e. None of the choices are correct
The expression of genetic traits is the
a. Genome
b. Genotype
c. Proteome
d. Phenotype
e. Proteotype
The gene of an operon that codes for a protein repressor is called the
a. Operator
b. Structural locus
c. Regulator
d. Promoter
e. None of the choices are correct
The jumping of a gene from one location to another is done by
a. Conjugation
b. Transposons
c. Transformation
d. Transduction
e. Transmission
The nontranscribed region of DNA to which RNA polymerase binds to initiate transcription is called the
a. Promoter
b. Operator
c. Operon
d. Exon
e. Intron
The site where the old DNA strands separate and new DNA strands will be synthesized is called the
a. Primer
b. Okazaki fragment
c. Template
d. Rolling circle
e. Replication fork
The transfer of DNA fragments from a dead cell to a live, competent recipient cell that results in a changed recipient cell is
a. Transduction
b. Conjugation
c. Transformation
d. Transmission
e. Mitosis
What type of mutation alters the base, but not the amino acid being coded for?
a. Silent
b. Back
c. Point
d. Nonsense
e. Missense
Which of the following is not a type of bacterial DNA recombination?
a. Transformation
b. Conjugation
c. Mitosis
d. Transduction
e. None of the above
Which of the following refers to the term metabolism?
A. all the reactions in a cell or organism
B. all the reactions in a cell that break down molecules only
C. all the reactions in a cell that build new molecules only
D. all the reactions in a cell that decompose molecules only
Which of the following best describes an endergonic reaction?
A. absorbs energy from the environment
B. is coupled with another reaction
C. is involved in biosynthesis
D. releases energy into the environment
Chemotrophs obtain their energy from which of the following?
A. inorganic chemical reactions only
B. light energy
C. organic chemical reactions only
D. organic and inorganic chemical reactions
Which of the following describes a molecule that had an electron removed?
A. anabolized
B. electronated
C. oxidized
D. reduced
Which of the following best describes the subcomponents of pyrophosphate?
A. two inorganic phosphate molecules
B. two organic phosphate molecules
C. three inorganic phosphate molecules
D. three organic phosphate molecules
Which molecule is often called the cell’s energy currency?
A. adenosine triphosphate
B. flavin adenine dinucleotide
C. nicotinamide adenine dinucleotide
D. nicotinamide adenine dinucleotide phosphate
Which site on an enzyme is where substrates bind?
A. the activation site
B. the active site
C. the catalyst site
D. the lock and key site
Which of the following are inorganic molecules that bind to enzymes?
A. apoenzymes
B. coenzymes
C. cofactors
D. holoenzymes
Which of the following best describes catabolic pathways?
A. They always absorb energy.
B. They break down large molecules into smaller components.
C. They build up large molecules from smaller components.
D. They must be coupled with the breakdown of ATP.
Which group comprises all lithotrophs?
A. algae
B. autotrophs
C. microbes
D. plants
Which is a common electron acceptor in catabolic reactions?
A. ATP
B. FADH2
C. NAD+
D. NADPH
The reaction that breaks down ATP to form ADP and inorganic phosphate is classified as which of the following?
A. endergonic
B. exergonic
C. nonspontaneous
D. reduction
Which of the following is an inhibitor that binds to the active site of an enzyme?
A. a competitive inhibitor
B. a noncompetitive inhibitor
C. an allosteric inhibitor
D. an uncompetitive inhibitor
Glycolysis produces a net gain of which of the following?
A. two ATP, two NADH, and two pyruvates
B. two ATP, two NADH, and four pyruvates
C. two ATP, four NADH, and two pyruvates
D. four ATP, two NADH, and two pyruvates
Which of the following is a pathway that breaks down glucose in some microbes?
A. the Calvin cycle
B. the Entner-Doudoroff pathway
C. the Krebs cycle
D. the tricarboxylic acid cycle
Which of the following best describes a transition reaction?
A. a reaction that converts pyruvate to acetyl CoA with the release of carbon dioxide
B. a series of reactions that convert citric acid to oxaloacetate
C. an optional reaction that transports pyruvate into the mitochondrion
D. the reaction that converts glucose to glucose-6-phosphate in glycolysis
Which of the following is not a product of the Krebs cycle?
A. carbon dioxide
B. GTP, which is converted to ATP
C. NADH
D. pyruvate
The Krebs cycle begins with the addition of acetyl CoA to which of the following?
A. citric acid
B. oxaloacetate
C. ribulose bisphosphate
D. succinate dehydrogenase
During the Krebs cycle, FAD is reduced to which of the following?
A. FADH
B. FADH2
C. NADH
D. NADH2
Which of the following is the purpose of fermentation?
A. to produce carbon dioxide
B. to produce large quantities of additional energy
C. to regenerate NAD+
D. to regenerate oxygen
ATP is produced through oxidative phosphorylation when which of the following occurs?
A. FADH2 donates electrons to succinate dehydrogenase
B. H+ moves through ATP synthase
C. NADH donates electrons to NADH dehydrogenase
D. the light-independent reactions fix CO2
Each pyruvate molecule contains how many carbon atoms?
A. two
B. three
C. four
D. six
When is the pentose phosphate pathway favored over other pathways to break down glucose?
A. when biosynthesis is not needed
B. when phospholipids are needed
C. when the cell has a severe energy deficit and needs energy rapidly
D. when the synthesis of nucleic acids and proteins is needed
Which of the following best defines chemiosmosis?
A. the disruption of the inner mitochondrial membrane, which dissipates energy
B. the movement of electrons from one acceptor to another
C. the movement of hydrogen ions through ATP synthase
D. the series of reactions that regenerate oxaloacetate
Why is the actual ATP yield of aerobic respiration often less than the maximum possible yield of 38 ATP?
A. Aerobic respiration competes with anaerobic respiration for energy.
B. Aerobic respiration competes with fermentation for energy.
C. In eukaryotes, energy is used to move molecules across membranes.
D. No organisms complete all parts of aerobic respiration.
Which of the following refers to the term metabolism?
a.all the reactions in a cell or organism
b.all the reactions in a cell that break down molecules only
c.all the reactions in a cell that build new molecules only
d.all the reactions in a cell that decompose molecules only
Which of the following best describes an endergonic reaction?
a.absorbs energy from the environment
b.is coupled with another reaction
c.is involved in biosynthesis
d.releases energy into the environment
Chemotrophs obtain their energy from which of the following?
a.inorganic chemical reactions only
b.light energy
c.organic chemical reactions only
d.organic and inorganic chemical reactions
Which of the following describes a molecule that had an electron removed?
a.anabolized
b.electronated
c.oxidized
d.reduced
Which of the following best describes the subcomponents of pyrophosphate?
a.two inorganic phosphate molecules
b.two organic phosphate molecules
c.three inorganic phosphate molecules
d.three organic phosphate molecules
Which site on an enzyme is where substrates bind?
a.the activation site
b.the active site
c.the catalyst site
d.the lock and key site
Which of the following best describes catabolic pathways?
a.They always absorb energy.
b.They break down large molecules into smaller components.
c.They build up large molecules from smaller components.
d.They must be coupled with the breakdown of ATP
Which group comprises all lithotrophs?
a.algae
b.autotrophs
c.microbes
d.plants
Which is a common electron acceptor in catabolic reactions?
a.ATP
b.FADH2
c.NAD+
d.NADPH
The reaction that breaks down ATP to form ADP and inorganic phosphate is classified as which of the following?
a.endergonic
b.exergonic
c.nonspontaneous
d.reduction
Which of the following is an inhibitor that binds to the active site of an enzyme?
a.a competitive inhibitor
b.a noncompetitive inhibitor
c.an allosteric inhibitor
d.an uncompetitive inhibitor
Glycolysis produces a net gain of which of the following?
a.two ATP, two NADH, and two pyruvates
b.two ATP, two NADH, and four pyruvates
c.two ATP, four NADH, and two pyruvates
d.four ATP, two NADH, and two pyruvates
Which of the following is a pathway that breaks down glucose in some microbes?
a.the Calvin cycle
b.the Entner-Doudoroff pathway
c.the Krebs cycle
d.the tricarboxylic acid cycle
Which of the following best describes a transition reaction?
a.a reaction that converts pyruvate to acetyl CoA with the release of carbon dioxide
b.a series of reactions that convert citric acid to oxaloacetate
c.an optional reaction that transports pyruvate into the mitochondrion
d.the reaction that converts glucose to glucose-6-phosphate in glycolysis
Which of the following is not a product of the Krebs cycle?
a.carbon dioxide
b.GTP, which is converted to ATP
c.NADH
d.pyruvate
The Krebs cycle begins with the addition of acetyl CoA to which of the following?
a.citric acid
b.oxaloacetate
c.ribulose bisphosphate
d.succinate dehydrogenase
Which of the following is the step in which CO2 enters the light-independent reactions (Calvin cycle)?
a.fixation
b.reduction
c.regeneration
d.transition
Carotenoids are pigments that are which of the following colors?
a.blue/green
b.green/orange
c.orange/yellow/red
d.purple/blue
Which of the following are enzymes that break down proteins?
a.amylases
b.oxidasesc.
oxygenases
d.proteases
Fatty acids are often degraded using which set of reactions
a.β-oxidation
b.glycolysis
c.photophosphorylation
d.the tricarboxylic acid cycle
Triglycerides are broken down by which of the following?
a.lipases
b.nitrogenases
c.phospholipases
d.proteases
During the Krebs cycle, FAD is reduced to which of the following
a.FADH
b.FADH2
c.NADH
d.NADH2
Which of the following is the purpose of fermentation?
a.to produce carbon dioxide
b.to produce large quantities of additional energy
c.to regenerate NAD+
d.to regenerate oxygen
ATP is produced through oxidative phosphorylation when which of the following occurs?
a.FADH2 donates electrons to succinate dehydrogenase
b.H+ moves through ATP synthase
c.NADH donates electrons to NADH dehydrogenase
d.the light-independent reactions fix CO2
Which of the following are inorganic molecules that bind to enymes?
Cofactors
A general term is applied to an inactive enzyme. An inactive enzyme that requires chemical modification before it becomes active is called a(n) .
Zymogen
Suppose a sequence of enzymatically catalyzed reactions converts substrate A to final product D through a sequence of reactions involving the production of intermediate products B and C as shown. Product D inhibits enzyme E1.
If the enzymes E1-E3 are all present in a test tube and substrate A is added to the reaction mixture, how will the concentration of intermediate B change?
E1 E2 E3
A B C D
First increase, then decrease
When A is added, some B will be produced, so its concentration will rise. As D is produced and begins to inhibit E1, the rate of production of B will fall. Since E2 causes C to be produced from B, the concentration of B will then fall.
What’s a term for a regulator substrate that binds to the regulatory site of an enzyme and changes the conformation of the active site?
Allosteric regulator
The regulator binds to the enzyme at a site that is not the active site and modifies the active site. We can’t tell if the regulation is positive or negative (we don’t know if the top or bottom form of the enzyme is active). We can’t say that this is a noncompetitive inhibitor because we don’t know if it inhibits or activates the enzyme.
The reaction of glucose with oxygen to produce carbon dioxide and water,
Glucose + 6O2 6CO2 + 6H2O has a ΔG° of -2880 kJ mol-1, making it a strongly exergonic reaction. However, a sample of glucose can be maintained indefinitely in an oxygen-containing atmosphere. How can these two facts be reconciled?
Although the reaction is exergonic, the activation energy barrier for the reaction is so high that the reaction occurs very slowly.
The large negative value for ΔG° indicates that this reaction is thermodyamically favorable. In order for the reaction to proceed, it must be possible for the reactants to overcome the reaction’s activation energy. If the activation energy barrier is very high, the forward rate constant for the reaction will be very slow. The forward rate constant in this case is so slow that no reaction will occur within the time of observation.
The reaction of glucose with oxygen is thermodynamically favored, as shown by the negative free-energy change. The fact that glucose can be maintained in an oxygen atmosphere is a reflection of the kinetic aspects of the reaction, requiring overcoming an activation-energy barrier.
An enzyme catalyzes the formation of ATP from ADP and phosphate ion. What is its effect on the rate of hydrolysis of ATP to ADP and phosphate ion?
Enzymes, like all catalysts, increase the rate of the forward and reverse reaction to the same extent.
The rate constant k for a reaction depends on the activation energy EA according to k = Ae-EA. Because the forward and reverse reactions must cross the same peak energy point in the reaction path, EA,f and EA,r are both equally affected by the catalyst. Thus, the forward and reverse rate constants will both increase by the same factor in the catalyzed reaction.
Which of the following are valid reasons for carrying out enzymatic reactions in buffer solutions?
A fair number of reactions produce H+ or OH – ions. It is important to buffer these ions, which could dramatically alter the reaction pH.
Solutions do not have to be buffered in order to dissolve enzymes.
The thermodynamics of most biochemical reactions are not particularly pH-dependent.
In many instances, a histidine residue in the active site participates in the catalytic mechanism, and the protonation state of the histidine’s imidazole side group is important to the mechanism. Likewise, the protonation states of a substrate or substrates in a reaction are often key to the proper interaction of the substrate with the enzyme active site.
It is quite common to find that the activity of an enzyme depends on the pH of the solution.
Other things being equal, what is a potential disadvantage of an enzyme having a very high affinity for its substrate?
The ES complex would be in an “energy trough,” with a consequentially large activation energy to the transition state.
-Tight enzyme-substrate binding will reduce the forward rate constant for the reaction.
-High affinity of the enzyme for the substrate will increase the activation energy of the forward reaction.
-The enzyme-substrate complex will be in a deep energy well, meaning that the enzyme-substrate complex will be more stable.
Tight binding of the substrate to the enzyme will change the amounts of free substrate and free enzyme as compared to the case in which the substrate-enzyme binding is weaker. The substrate concentration is usually in excess compared to the enzyme concentration, so this small change will have little effect on the reaction kinetics.
It is unlikely that distortion of the active site due to tight binding would occur. The enzyme is much larger than the substrate and thus not likely to deform.
Tight enzyme-substrate binding will reduce the forward rate constant for the reaction. One can imagine that a tightly bound substrate would not readily alter its shape as it moves through the transition state toward products.
High affinity of the enzyme for the substrate will decrease the energy of the enzyme-substrate complex, therefore, increasing the energy required to form the enzyme-transition state complex (the activation energy of the forward reaction).
Enzyme inhibition can be overcome under some, but not all, conditions. Under what conditions can inhibition be overcome?
A competitive inhibitor can always be overcome by the addition of enough substrate, while a noncompetitive inhibitor can never be overcome.
Where do lines intersect on a Lineweaver-Burk plot showing competitive inhibition?
y axis intercept
1/Vmax
A competitive inhibitor will alter the apparent KM of an enzyme-substrate combination but will not alter the apparent Vmax value bc blocks binding, not catalysis.. On a Lineweaver-Burk plot for a competitive inhibitor, the plots for separate experiments at different inhibitor concentrations will intersect on the 1/V axis.
For a competitive inhibitor, a Lineweaver-Burk plot containing data for separate experiments at different inhibitor concentrations will intersect on the 1/V axis at the point 1/[S] = 0 and 1/V = 1/Vmax.
Where do lines intersect on a Lineweaver-Burk plot showing non-competitive inhibition?
x axis intercept
-1/Km
For a noncompetitive inhibitor, a Lineweaver-Burk plot containing data collected at two different inhibitor concentrations will form plots that intersect on the 1/[S] axis at the point 1/[S] = -1/KM and 1/V = 0.
A noncompetitive inhibitor will alter the apparent Vmax of an enzyme-substrate combination but will not alter the apparent KM value. On a Lineweaver-Burk plot, data collected at two different inhibitor concentrations will form plots that intersect on the 1/[S] axis.
Pure noncompetitive inhibition
The binding of the inhibitor does not change the affinity of the enzyme for substrate at all and vice versa; thus the does not change.
Doesn’t alter observed Km bc does not change the affinity of the enzyme for its substrate.
Because the inhibitor can bind to E or to ES equally well, any time there is inhibitor present, some of the enzyme will be tied up in the EIS form, which does not lead to catalysis. For this reason it would appear that less enzyme is present.
Mixed inhibition
the substrate and inhibitor do affect each other such that the for the substrate is different in the presence of inhibitor.
Why does the apparent decrease in the presence of an uncompetitive inhibitor?
The binding of inhibitor to the ES complex to form EIS removes some of the ES. By LeChatelier’s principle, this will tend to force the reaction to the right forming more ES. By stimulating the binding of E and S in this manner, the graph will show that the is reduced.
What is a suicide substrate? Why are they important?
It is a substrate that binds irreversibly to the active site, permanently inactivating the enzyme. They are important because they can be used as potent drugs to knock out an enzyme, and they are used to study enzyme kinetics with a focus on interactions at the active site.
If we made a Lineweaver-Burk plot of an irreversible inhibitor, which type of reversible inhibition would it be most likely to resemble?
pure non-competitive
The pH dependence of the rate of the reaction catalyzed by the enzyme fumarase shows that the rate is very low at pH 5, it is maximal at pH 6.5, and it is very low at pH 9.
This pH dependence is due to ionization of important amino acid residues in fumarase or in the substrate of the reaction, fumarate.
True
Doubling the concentration of enzyme present in a reaction will double the rate of the reaction that the enzyme catalyzes.
True
The rate of an enzymatically catalyzed reaction is directly proportional to the concentration of enzyme present.
Increasing the temperature of an enzyme-catalyzed reaction will always increase the rate of the reaction.
False
Enzymes exhibit a temperature optimum, so increasing T will not necessarily increase the rate of reaction. For example, if the T optimum was 35 °C and the temperature of the reaction was also at 35 °C, increasing T would only move the enzyme away from its optimal temperature and the rate of the reaction would decrease.
Suppose that a particular enzyme and substrate combination exhibit a maximal reaction rate of 10 micromolar/min. Now suppose you add an inhibitor and the maximal rate is still 10 micromolar/min. What sort of inhibitor is this?
Competitive
Since the maximal rate of the reaction is not altered when the inhibitor is present, this must be a competitive inhibitor. The maximal rate is just the fastest rate of production of product when the substrate concentration is very large (in mathematical terms, when [S] infinity). This says that S can eventually displace all I from the enzyme, so the maximal rate of the reaction is determined by the amount of enzyme that is present.
Suppose that a particular enzyme and substrate combination exhibit a maximal reaction rate of 10 micromolar/min. Now suppose you add an inhibitor and the maximal rate is 5 micromolar/min. What sort of inhibitor is this?
Noncompetitive
Since the maximal rate of the reaction is reduced when the inhibitor is present, this must be a noncompetitive inhibitor. The maximal rate is just the fastest rate of production of product when the substrate concentration is very large (in mathematical terms, when [S] infinity).
Competitive inhibition fits both the lock-and-key model and the induced-fit model of enzyme action.
True
In terms of enzyme nomenclature, what is a K system?
An allosteric enzyme in which the binding of an effector alters the apparent affinity of the enzyme for its substrate without changing the apparent Vmax of the reaction.
In terms of enzyme nomenclature, what is a V system?
An allosteric enzyme in which the binding of an effector alters the apparent Vmax of the enzyme-substrate reaction without altering the affinity of the enzyme for its substrate. An allosteric enzyme system for which the activator will increase the apparent Vmax of the reaction converting substrate to product
How is the cooperative behavior of an allosteric enzyme uniquely reflected in a plot of the reaction rate versus the substrate concentration?
~When the cooperativity is negative, the V vs. [S] plot becomes more sharply curved than a hyperbola.
~Both positive and negative cooperativity cause the V vs. [S] plot to deviate from the hyperbolic plot of a Michaelis-Menten enzyme.
~The V vs. [S] curve is sigmoidal when the cooperativity is positive.
~The degree of cooperativity is reflected in the extent of curvature of the V vs. [S] plot.
~The V vs. [S] plot is not shaped like that of a hyperbolic function.
~When the cooperativity is negative, the V vs. [S] plot becomes more sharply curved than a hyperbola.
What property of a metal ion makes it a useful cofactor in enzyme-mediated catalysis?
Tt can act as a Lewis acid
A metal with an excess complement of electrons can readily donate a lone pair of electrons, forming a metal ion. Metal ions are electron deficient and can act as Lewis acids, accepting electrons into unoccupied d-orbitals to form metal complexes.
The donation of electrons from a Lewis base (the substrate in the case of enzyme-mediated catalysis) can cause electronic strain on other bonds in the substrate, weakening them and making them easier to break.
How are coenzymes and vitamins related?
Vitamins are often the precursor molecules that are metabolized to the active coenzymes. For example, vitamin B6 is converted to pyridoxal phosphate, niacin is the precursor of NADH, and flavin adenine dinucleotide is derived from riboflavin.
An enzyme that transfers a phosphate moiety in a reaction is called a ___________. The most common source of phosphate for biochemical reactions is ___________.
Kinase, ATP
concerted model
Proposed by Monod, Wyman, and Changeaux. It asserts that the binding of substrate to one enzyme subunit causes a conformational change in that subunit that is immediately transferred to all other subunits. This conformational change alters the affinity of all subunits for the substrate.
The binding of substrate, inhibitor, or activator to one subunit shifts the equilibrium between an active form of the enzyme, which binds substrate strongly, and an inactive form, which does not bind substrate strongly.
The conformational change takes place in all subunits at the same time. In the sequential model, the binding of substrate induces the conformational change in one subunit, and the change is subsequently passed along to other subunits.
sequential model
by Daniel Koshland, proposes that the binding of substrate to an enzyme subunit induces a conformational change in the subunit that then makes other subunits more likely to change conformation. The conformational change alters the affinity of the subunit for the substrate. Not all enzyme subunits need to be in the same conformation.
Allosteric enzymes
-usually have multiple subunits
-can involve product feedback activation
-Their V versus [S] plots yield sigmoid- or S-shaped curves
Deviations from linearity are characteristic of the kinetics of regulatory enzymes known as allosteric enzymes. Allosteric enzymes are usually multisubunit proteins in which the subunits interact with each other. The interaction alters the activity of the enzyme toward the kinetics of the S P reaction.
Inhibition of a regulatory enzyme by a feedback inhibitor does not conform to any normal inhibition pattern and the feedback inhibitor bears little structural similarity to the substrate for the regulatory enzyme. Regulatory or allosteric enzymes are, in some instances, regulated by activation. That is, whereas some effector molecules exert negative effects on enzyme activity, other effectors show stimulatory, or positive, influences on activity.
Michaelis-Menten Enzymes
-never involves product feedback activation
-Their V versus [S] plots yield rectangular hyperbolas
Nucleophilic catalysis
In the first step of the reaction, the serine hydroxyl is the nucleophile that attacks the substrate peptide bond. In the second step, water is the nucleophile that attacks the acyl-enzyme intermediate.
SN1
unimolecular nucleophilic substitution. The unimolecular part means that it obeys first-order kinetics. If the reaction is R:X +Z: –> R:Z + X , with an reaction, the rate depends on the speed with which the X breaks away from the R. The Z group comes in later and quickly, compared with the breakdown of R:X.
~leads to loss of stereospecificity as the X group leaves before the entering nucleophile. planar intermediate is formed. This means that the nucleophile can attack from above or below the plane, leading to different isomers.
SN2
bimolecular nucleophilic substitution. This happens with the same reaction scheme if the Z attacks the R:X molecule before it breaks down. Thus, the concentration of both R:X and Z: are important, and the rate displays second-order kinetics.
Oxidation-reduction
Nicotinamide adenine dinucleotide
flavin adenine dinucleotide
Acyl transfer
coenzyme A
lipoic acid
Transamination
pyridoxal phosphate
Carboxylation
biotin
Aldehyde transfer
Thiamine pyrophosphate
One carbon unit transfer
tetrahydrofolic
A bacteriophage transfers DNA of the previous host to the current host. This is an example of
a. Conjugation
b. Generalized transduction – correct
c. Specialized transduction
d. Creation of an Hfr cell
e. None of the choices are correct
A frameshift is caused by ______ mutations?
a. Missense and insertion
b. Missense and nonsense
c. Nonsense and deletion
d. Deletion and insertion – correct
e. Insertion and nonsense
A nucleosome is a linear chromosome wound around the
a. Nuclear membrane
b. rRNA
c. mRNA
d. Histone – correct
e. Nucleolus
A permanent, inheritable change in the genetic information is called a(n)
a. Translation
b. Transcription
c. Mutation – correct
d. Alteration
e. Regeneration
A primer of ____ is needed at the origin of nucleotide addition.
a. Polymerase III
b. Polymerase I
c. Helicase
d. RNA – correct
e. DNA
A sequence of bases on a gene that does not code for protein is called a/an
a. Promoter
b. Operator
c. Operon
d. Exon
e. Intron – correct
All of the following pertain to transcription except
a. Occurs on a ribosome in the cytoplasm – correct
b. Occurs before translation
c. Requires RNA polymerase
d. Requires a template DNA strand
e. Is a process of protein synthesis
Among the microorganisms, various genomes can include
a. Chromosomes
b. Plasmids
c. Mitochondrial DNA
d. Chloroplast DNA
e. All of the choices are correct – correct
Bacterial conjugation involves
a. Bacteriophage carrying donor DNA to the recipient cell
b. A donor cell with a plasmid that synthesizes a pilus – correct
c. Naked DNA fragments from a lysed donor cell are taken up by a recipient cell
d. New progeny cells with genes from two parent bacterial cells
e. None of the choices are correct
Base pairs in DNA are held together by _____ bonds.
a. Peptide
b. Non polar covalent
c. Polar covalent
d. Hydrogen – correct
e. Sulfhydryl
DNA Polymerase I
a. Removes primers – correct
b. Adds bases to new DNA chain
c. Seals DNA gaps
d. Proofreads DNA chain
e. All of the choices are correct
DNA polymerase III
a. Is needed for adding nucleotides during mRNA synthesis
b. Synthesizes new DNA only in the 5′ to 3′ direction – correct
c. Cannot add nucleotides to the lagging strand
d. Synthesizes an RNA primer
e. All of the choices are correct
Each nucleotide is composed of
a. One phosphate, one nitrogenous base, one sugar – correct
b. One phosphate, one nitrogenous base, two sugars
c. Two phosphates, one nitrogenous base, one sugar
d. Two phosphates, one nitrogenous base, two sugars
e. One phosphate, two nitrogenous bases, one sugar
Eukaryotic chromosomes differ from prokaryotic chromosomes because only eukaryotes have
a. Histone proteins
b. Chromosomes in a nucleus
c. Several to many chromosomes
d. Elongated, not circular, chromosomes
e. All of the choices are correct – correct
Gene regulation can involve a protein repressor that blocks _____ from initiating transcription.
a. DNA polymerase I
b. DNA polymerase III
c. RNA polymerase – correct
d. mRNA
e. rRNA
Groups of three consecutive bases along the DNA of a gene have the code for one
a. Protein
b. Nucleotide
c. Amino acid – correct
d. Purine
e. None of the choices are correct
Helicase
a. Unwinds DNA – correct
b. Supercoils DNA
c. Unwinds RNA
d. Winds RNA
e. None of the choices are correct
If the wild type DNA sequence reads THE CAT ATE THE BIG RAT, what type of mutation would change the sequence to THE CAT ATA ETH EBI GRA T?
a. Missense
b. Nonsense
c. Insertion – correct
d. Deletion
e. Silent
If the wild type DNA sequence reads THE CAT ATE THE BIG RAT, what type of mutation would change the sequence to THE CAT ATE (stop)?
a. Missense
b. Nonsense – correct
c. Insertion
d. Deletion
e. Silent
If you have the sequence of mRNA that is AUAUGC, then the DNA antisense strand is ____.
a. AUAUGC
b. UAUACG
c. TATACG – correct
d. CGUAUA
RNA molecules differ from DNA molecules because only RNA
a. Has ribose
b. Has uracil
c. Is typically one strand of nucleotides
d. Does not have thymine
e. All of the choices are correct – correct
RNA polymerase binds to the
a. Start codon
b. Termination sequence
c. Regulation sequence
d. Promoter sequence – correct
e. None of the choices are correct
Semiconservative replication refers to
a. Each base bonding at the 1′ position of the sugar
b. A purine always bonding to a pyrimidine
c. One helix strand that runs from the 5′ to 3′ direction and the other strand runs from the 3′ to 5′ direction
d. An original parent DNA strand and one newly synthesized DNA strand comprising a new DNA molecule – correct
e. None of the choices are correct
The DNA of microorganisms is made up of subunits called
a. Histones
b. Amino acids
c. Nucleotides – correct
d. mRNA
e. Polymerases
The RNA molecules that carry amino acids to the ribosomes during protein synthesis are called
a. Ribosomal RNA
b. Messenger RNA
c. Transfer RNA – correct
d. Primer RNA
e. Ribozymes
The _____ is all of the genetic material of a cell.
a. Chromosome
b. Plasmid
c. Prophage
d. Genome – correct
e. Proteome
The antiparallel arrangement within DNA molecules refers to
a. Each base bonding at the 1′ position of the sugar
b. A purine always bonding to a pyrimidine
c. One helix strand that runs from the 5′ to 3′ direction and the other strand runs from the 3′ to 5′ direction – correct
d. An original parent DNA strand and one newly synthesized DNA strand comprising a new DNA molecule
e. None of the choices are correct
The expression of genetic traits is the
a. Genome
b. Genotype
c. Proteome
d. Phenotype – correct
e. Proteotype
The gene of an operon that codes for a protein repressor is called the
a. Operator
b. Structural locus
c. Regulator – correct
d. Promoter
e. None of the choices are correct
The jumping of a gene from one location to another is done by
a. Conjugation
b. Transposons – correct
c. Transformation
d. Transduction
e. Transmission
The nontranscribed region of DNA to which RNA polymerase binds to initiate transcription is called the
a. Promoter – correct
b. Operator
c. Operon
d. Exon
e. Intron
The site where the old DNA strands separate and new DNA strands will be synthesized is called the
a. Primer
b. Okazaki fragment
c. Template
d. Rolling circle
e. Replication fork – correct
The transfer of DNA fragments from a dead cell to a live, competent recipient cell that results in a changed recipient cell is
a. Transduction
b. Conjugation
c. Transformation
d. Transmission – correct
e. Mitosis
What type of mutation alters the base, but not the amino acid being coded for?
a. Silent – correct
b. Back
c. Point
d. Nonsense
e. Missense
Which of the following is not a type of bacterial DNA recombination?
a. Transformation
b. Conjugation
c. Mitosis – correct
d. Transduction
e. None of the above