test bank 4
The protein in the mitochondria that captures the kinetic energy of moving H+ ions and converts it to the stored energy of ATP is called A) ATP synthase. B) lactate dehydrogenase. C) oxidative phosphorylase. D) glucokinase.
A) ATP synthase.
Transcription of the DNA triplet sequence ATC yields A) UAG. B) TAG. C) UTC. D) ATC.
A) UAG.
An allosteric modulator binds to A) a region of the enzyme other than the active site. B) the active site. C) the substrate. D) the product. E) the surrounding tissue.
A) a region of the enzyme other than the active site.
The rate of product formation by an enzyme-catalyzed reaction would be increased by A) adding more substrate molecules. B) adding more product molecules. C) reducing the number of enzymes. D) reducing the number of substrate molecules.
A) adding more substrate molecules.
Isozymes A) are enzymes with a slightly different structure that catalyze the same reaction. B) are enzymes with the same structure that catalyze different reactions. C) are inorganic molecules that bind to and thereby activate enzymes. D) are the inactive form of an enzyme.
A) are enzymes with a slightly different structure that catalyze the same reaction.
If the enzyme RNA polymerase was completely inhibited within a cell, it could not A) form proteins. B) form complementary sequences of DNA. C) link pieces of DNA together. D) form spindle fibers. E) form a new nuclear membrane during cell division.
A) form proteins.
An enzyme that adds or subtracts water molecules is a A) hydrolase. B) lipase. C) transferase. D) ligase. E) kinase.
A) hydrolase.
Enzymes increase reaction rate by A) lowering the activation energy of a reaction. B) increasing the free energy in the products. C) raising the activation energy of a reaction. D) converting an endergonic reaction to an exergonic reaction.
A) lowering the activation energy of a reaction.
Transcription occurs in the ________ of the cell. A) nucleus B) cytoplasm C) Golgi apparatus D) smooth endoplasmic reticulum E) plasma membrane
A) nucleus
An example of transamination is A) removing an amine group from one molecule and binding it to a different molecule. B) removing an amino group and putting it into the bloodstream for the kidneys to discard. C) removing a phosphate group from a molecule. D) finding a brand new sports car in your driveway with your name on it.
A) removing an amine group from one molecule and binding it to a different molecule.
The TAC sequence of DNA is the ________ of a coding sequence that is preceded by the ________ that regulates transcription. A) start, promoter region B) start, intron C) stop, promoter region D) stop, intron
A) start, promoter region
According to the second law of thermodynamics, A) the amount of entropy in living systems increases without the input of energy. B) entropy decreases in living systems that are not receiving energy. C) energy can be converted, but not be created nor destroyed. D) the total amount of energy in the universe never changes.
A) the amount of entropy in living systems increases without the input of energy.
When a chemical reaction is in equilibrium, A) there is no net change in the amount of substrates or products. B) the reaction is proceeding at its maximum rate. C) the reaction has stopped. D) there are equivalent amounts of substrates and products.
A) there is no net change in the amount of substrates or products.
Following post-translational modification, any misfolded protein will be destroyed by A) ubiquitin. B) chaperones. C) methylation. D) ribonucleases.
A) ubiquitin.
What are the advantages of using ATP as the energy-transferring molecule in a cell?
ATP easily acquires the energy stored in complex biomolecules such as carbohydrates and its phosphate bonds are readily broken to release energy.
The activity of metabolic pathways is influenced by the ratio of ________.
ATP to ADP
Cells normally regulate the rate of an enzymatic reaction by A) raising their temperature to 110° F. B) changing the concentration of an enzyme. C) increasing reaction rate as the concentration of product increases. D) allowing all metabolic enzymes to be found throughout the cytoplasm.
B) changing the concentration of an enzyme.
Explain how these statements differ, and identify which one(s) is/are correct. Explain what is wrong with each incorrect statement. Explain when chemical reactions continue and when they stop. A. A chemical reaction proceeds until the enzyme molecules are all consumed. B. A chemical reaction proceeds until the substrate molecules are all consumed. C. A chemical reaction proceeds until equilibrium is established. D. A chemical reaction proceeds until all the product molecules are removed.
B and C are correct as written, but B requires some clarification. A is incorrect because enzyme molecules are not consumed in chemical reactions and will continue to be active until acted upon by environmental conditions (temperature, pH, or modifiers). B is correct only when the product is removed from the system. If the product remains, the enzyme will reach equilibrium where the ratio of substrate to product is constant (Correct Answer C). In D, if the product of the reaction is removed, the reaction would continue to proceed to form new product (assuming enzymes and substrates are available). Chemical reactions continue if conditions are favorable, including presence of substrate and enzyme and fairly constant temperature and pH. In living systems, most chemical reactions do not have a steady supply of substrate; for example, the chemical reactions of digestion will stop when the small intestine is empty.
What is the potential yield of ATP molecules for each FADH2 molecule entering the electron transport system? A) 1 B) 1.5 C) 2 D) 2.5 E) 3
B) 1.5
When energy is released during catabolism, it is temporarily trapped in high energy bonds or electrons of certain compounds. Which of the following is NOT associated with carrying energy? A) ATP B) DNA C) NADH D) FADH2 E) NADPH
B) DNA
The enzymes that synthesize mRNA from the start codon are called A) ribonucleases. B) RNA polymerases. C) DNA polymerases. D) ATP synthases. E) lactate dehydrogenases.
B) RNA polymerases.
Why is there a range of 30-32 ATP molecules produced from one glucose molecule? A) Sometimes the electron transport system is more efficient than other times. B) The NADH molecules produced during glycolysis are in the cytoplasm; occasionally, electrons are carried by the lower energy FADH2 instead of NADH. C) Individual variation is normal among cells. D) Any of these answers may work under different cellular conditions.
B) The NADH molecules produced during glycolysis are in the cytoplasm; occasionally, electrons are carried by the lower energy FADH2 instead of NADH.
In order to slow generation of product from a particular biochemical pathway within a cell, the intermediates formed by that pathway A) are removed from the cell more quickly. B) accumulate inside the cell. C) are rapidly converted into. D) become toxic to the cell.
B) accumulate inside the cell.
The tRNA molecule contains the three-base sequence called the A) codon. B) anticodon. C) semicodon. D) aminocodon.
B) anticodon.
In the absence of a signal sequence, a newly synthesized protein localizes to the A) mitochondria. B) cytoplasm. C) peroxisome. D) nucleus. E) plasma membrane.
B) cytoplasm.
All of the triplet codes needed to produce exactly one functional piece of RNA are found in one A) chromosome. B) gene. C) codon. D) anticodon. E) None of the answers are correct.
B) gene.
Compartmentation refers to A) pairing together isozymes that perform similar reactions. B) grouping related enzymes into specific organelles. C) separating substrates into chemical classes. D) dividing metabolic reactions into groups for better understanding.
B) grouping related enzymes into specific organelles.
A molecule that loses electrons during a reaction is A) reduced. B) oxidized. C) dehydrated. D) hydrated.
B) oxidized.
In the aerobic metabolism of glucose, ________ acts as the final electron acceptor. A) water B) oxygen C) carbon dioxide D) lactate E) ATP
B) oxygen
Which of the following is a key intermediate of glucose catabolism to the citric acid cycle? A) ATP B) pyruvate C) oxygen D) lactate E) glucokinase
B) pyruvate
The binding sites of enzymes are A) products of an enzymatic reaction. B) regions of an enzyme that are involved in bringing substrates together. C) bonds between the substrate and certain amino acids. D) not necessarily involved in a reaction.
B) regions of an enzyme that are involved in bringing substrates together.
An exergonic chemical reaction A) converts substrates into products that have more free energy. B) releases energy as the reaction progresses. C) requires the input of energy. D) requires an enzyme in order to overcome the activation energy.
B) releases energy as the reaction progresses.
The template strand of DNA A) is not involved in mRNA synthesis. B) serves as a guide for mRNA synthesis. C) includes the base uracil. D) is alternatively spliced to generate the exon.
B) serves as a guide for mRNA synthesis.
A competitive inhibitor binds to A) a region of the enzyme other than the active site. B) the active site. C) the substrate. D) the product. E) the surrounding tissue.
B) the active site.
Energy is defined as A) doing tasks that make you tired. B) the capacity to do work. C) the light and heat from the sun. D) using glucose to synthesize ATP.
B) the capacity to do work.
A reversible reaction is one where A) there are large changes in the net free energy from substrate to product. B) there are small changes in the net free energy from substrate to product. C) there is no change in the net free energy from substrate to product. D) a reaction between products is unlikely due to the high activation energy.
B) there are small changes in the net free energy from substrate to product.
The process of forming mRNA is called A) replication. B) transcription. C) translation. D) ribolation. E) protein synthesis.
B) transcription.
The net energy yield for the anaerobic metabolism of one glucose molecule is A) 2 ATP and 2 NADH. B) 0 ATP and 2 NADH. C) 2 ATP and 0 NADH. D) 2 ATP and 2 FADH2. E) 2 ATP, 6 NADH, and 2 FADH2.
C) 2 ATP and 0 NADH.
For each NADH molecule that moves through the electron transport system, what is the potential yield of ATP molecules? A) 1 B) 2 C) 2.5 D) 3.5 E) 4
C) 2.5
Enzymes are often useful as diagnostic tools. How? A) Enzymes destroy pathogenic bacteria so blood levels of bacteria decline. B) Enzymes destroy damaged cells so X-rays reveal smaller body organs. C) Damaged cells release enzymes into the blood that can be detected. D) The liver releases enzymes that accumulate in the urine.
C) Damaged cells release enzymes into the blood that can be detected.
Transcription of the DNA triplet sequence CAT will bind to the tRNA bearing A) CAT. B) GTA. C) GUA. D) ATU.
C) GUA.
What is the result of alternative splicing of mRNA? A) A new gene is produced. B) The DNA is replicated. C) Isoenzymes are produced from a single gene. D) Genes are mutated. E) Proteins isomerize.
C) Isoenzymes are produced from a single gene.
What happens to the oxygen that is metabolized within the mitochondria? A) The oxygen is converted to CO2. B) The oxygen is incorporated into organic molecules during cellular metabolism. C) The oxygen is combined with hydrogen to form water. D) The oxygen acts as a coenzyme in the production of ATP. E) The oxygen is converted to CO2 and is combined with hydrogen to form water.
C) The oxygen is combined with hydrogen to form water.
Organic molecules that act as receptors/carriers for the cleaved portion of the substrate are A) vitamins. B) isoenzymes. C) coenzymes. D) modulators.
C) coenzymes.
The reactions of glycolysis occur in the cell's ________; the reactions of the citric acid cycle occur in the ________. A) cytoplasm, cytoplasm B) mitochondria, mitochondria C) cytoplasm, mitochondria D) mitochondria, cytoplasm
C) cytoplasm, mitochondria
Changes in environmental pH or temperature will cause the reaction rate for an enzyme to A) increase. B) decrease. C) either increase or decrease depending upon enzyme properties. D) not change.
C) either increase or decrease depending upon enzyme properties.
Oxidative phosphorylation occurs ________; the beneficial end product is ________. A) in the cytoplasm just inside the plasma membrane, H2O B) in the cytoplasm just inside the plasma membrane, ATP C) in the mitochondria due to the electron transport system, ATP D) in the mitochondria due to the electron transport system, CO2 E) twice during the citric acid cycle, ATP
C) in the mitochondria due to the electron transport system, ATP
To activate a regulated gene, the formation of mRNA is ________ by the binding of ________ to the promoter. A) repressed, transcription factors B) repressed, translation factors C) induced, transcription factors D) induced, translation factors
C) induced, transcription factors
The activity of an enzyme is changed by environmental factors such as temperature or pH; these factors are referred to as A) specificity. B) common bond. C) modulators. D) isozyme. E) product.
C) modulators.
Information stored in the nucleus is translated into A) carbohydrates. B) lipids. C) proteins. D) phospholipids. E) None of the answers are correct.
C) proteins.
Inside the matrix of the mitochondria, pyruvate A) is converted to acetyl CoA which requires energy from an NADH. B) gains a carbon in its conversion to acetyl CoA. C) requires the vitamin pantothenic acid for its conversion to acetyl CoA. D) is converted to lactate under anaerobic conditions.
C) requires the vitamin pantothenic acid for its conversion to acetyl CoA.
When an enzyme is working as fast as it can because its active site is continually refilled with substrate, the condition is referred to as A) allosteric modulation. B) equilibrium. C) saturation. D) the Ricardo-Mertz phenomenon. E) specificity.
C) saturation.
Activation energy is A) the energy lost or gained in a reaction. B) the energy required for an endergonic reaction. C) the energy required to bring molecules into a position where they can interact. D) required to convert an endergonic reaction to an exergonic reaction.
C) the energy required to bring molecules into a position where they can interact.
An enzyme that transfers chemical groups among substrates is a A) hydrolase. B) lipase. C) transferase. D) ligase. E) kinase.
C) transferase.
How would the lack of a required cofactor for an enzyme affect that enzyme's function? A) The enzyme's function would not be altered. B) The enzyme would function more slowly. C) The enzyme would function more quickly. D) The enzyme would not be able to function.
D) The enzyme would not be able to function.
NADH is produced from each reaction described EXCEPT one. Identify the exception. A) during aerobic glycolysis B) during the conversion of pyruvate to acetyl CoA C) during the citric acid cycle D) during anaerobic glycolysis
D) during anaerobic glycolysis
Which of these results in a REDUCED molecule? A) loss of phosphate B) gain of phosphate C) loss of electrons D) gain of electrons
D) gain of electrons
End-product inhibition describes the process whereby A) decreasing amounts of substrate reduce activity of the enzyme. B) decreasing amounts of product reduce activity of the enzyme. C) increasing amounts of substrate reduce activity of the enzyme. D) increasing amounts of product reduce activity of the enzyme. E) increasing amounts of product reduce activity of all enzymes in the vicinity.
D) increasing amounts of product reduce activity of the enzyme.
During starvation, steroid hormones trigger the transcription of genes for lipid metabolism in their target cells. This would be an example of control by A) negative feedback. B) positive feedback. C) repressors. D) inducers. E) alternative splicing.
D) inducers.
Once synthesized, the ________ of mRNA are removed through ________, which results in the formation of the coding sequence of a protein. A) exon, RNA interference B) exon, alternative splicing C) intron, RNA interference D) intron, alternative splicing
D) intron, alternative splicing
ATP synthase transfers the ________ energy of the H+ ions to the high-energy phosphate bond of ________. A) potential, NADH B) potential, ATP C) kinetic, NADH D) kinetic, ATP E) None of the answers are correct.
D) kinetic, ATP
An enzyme that joins two substrates using energy is a A) hydrolase. B) lipase. C) transferase. D) ligase. E) kinase.
D) ligase.
The addition of a phosphate group to a substrate is called ________. The enzyme that catalyzes this reaction is referred to as a ________. A) proteolysis, phosphatase B) phosphorylation, phosphatase C) proteolysis, kinase D) phosphorylation, kinase
D) phosphorylation, kinase
Aerobic metabolism of glucose A) requires oxygen. B) produces more ATP per glucose than anaerobic pathways. C) is the fastest way to produce glucose. D) requires oxygen and produces more ATP per glucose than anaerobic pathways.
D) requires oxygen and produces more ATP per glucose than anaerobic pathways.
Increasing ________ will decrease the amount of mRNA transcript within a cell for a constitutively active gene. A) ribonuclease activity only B) RNA polymerase activity only C) siRNA concentration only D) ribonuclease activity and siRNA concentration only E) ribonuclease activity, RNA polymerase activity and siRNA concentration
D) ribonuclease activity and siRNA concentration only
The ________ of glycogen from many glucose molecules is an ________ reaction. A) decomposition, endergonic B) synthesis, exergonic C) decomposition, exergonic D) synthesis, endergonic
D) synthesis, endergonic
After forming a complex with the ribosome, mRNA interacts with a third molecule. This molecule is called A) DNA. B) an amino acid. C) rRNA. D) tRNA. E) rough ER.
D) tRNA.
The explanation for how ATP bonds are actually formed during oxidative phosphorylation is called A) the Krebs hypothesis. B) the second law of thermodynamics. C) the proton principle. D) the chemiosmotic theory. E) Murphy's law.
D) the chemiosmotic theory.
Chemical reactions in a living system function to A) only transfer energy from one molecule to another. B) create new energy. C) only use energy stored in a molecule. D) transfer energy from one molecule to another or use energy stored in a molecule.
D) transfer energy from one molecule to another or use energy stored in a molecule.
Regulatory-protein transcription factors bind to ________ and activate ________, which tells the RNA polymerase ________.
DNA, promoter, where to bind to the DNA
Phosphate groups may be transferred from one molecule to another during A) hydrolysis reactions only. B) addition reactions only. C) dehydration reactions only. D) exchange reactions only. E) addition and exchange reactions.
E) addition and exchange reactions.
When an enzyme's activity is destroyed by heat or a change in pH, the enzyme is said to be A) broken. B) toxic. C) conjugated. D) tertiary. E) denatured.
E) denatured.
Which can serve as substrates for ATP production? A) glucose only B) amino acids only C) fatty acids only D) glucose and fatty acids only E) glucose, amino acids and fatty acids
E) glucose, amino acids and fatty acids
An enzyme that transfers phosphates from ATP to a substrate molecule is a A) hydrolase. B) lipase. C) transferase. D) ligase. E) kinase.
E) kinase.
The general term that describes energy stored in chemical bonds is A) thermodynamics. B) bioenergetics. C) entropy. D) kinetic energy. E) potential energy.
E) potential energy.
________ generated in the ________ enter the electron transport system to generate 2.5 ATP molecules.
NADH, mitochondria
________ describes how much product is generated or substrate destroyed within a period of time.
Reaction rate
Explain how these statements differ, and identify which one(s) is/are correct. Explain what is wrong with each incorrect statement. A. A chemical reaction is at equilibrium when there is no further change in substrates. B. A chemical reaction is at equilibrium when the amounts of substrates and product no longer change. C. A chemical reaction stops when it reaches equilibrium. D. A chemical reaction is at equilibrium when the amount of substrate equals the amount of product.
Only B is correct as written. A could be corrected by clarifying that it is concentration or amount of substrate that ceases to change; individual molecules can form or break at any given time, but the overall amount will not change because synthesis will be balanced by degradation. C is incorrect because the reactions continue as long as conditions such as presence of catalysts, favorable temperature, and presence of substrates are maintained. As a given enzyme can both synthesize and degrade, both processes will continue even at equilibrium. D is incorrect because at equilibrium there is no net change in amounts, but it is not necessary for concentrations of substrates and products to be the same as each other.
Briefly describe oxidation-reduction reactions. What does it mean for a molecule to be reduced or oxidized? Identify and explain the mnemonic device provided in the text for oxidation and reduction reactions. See if you can make one up yourself.
Oxidation-reduction reactions occur when electrons are transferred from one molecule to another. The molecule that is oxidized in the reaction loses electrons while the reduced molecule gains electrons. OIL RIG (oxidation is loss, reduction is gain) is the mnemonic provided in the textbook.
Describe the four types of enzymatic reactions.
Oxidation-reduction reactions transfer electrons or protons between substrates. Hydrolysis-dehydration reactions form or break a chemical bond between organic substrates by removing or adding a water molecule. Transfer reactions (addition-subtraction-exchange reactions) add, remove, or exchange a functional group (phosphate or amino groups) among the substrates. Ligation reactions join molecules using the energy from an ATP molecule.
Compare and contrast potential energy with kinetic energy.
Potential energy is the energy an object has stored in its position, while kinetic energy is energy associated with a moving object/movement.
________ is the process which blocks translation.
RNA interference
The enzyme ________ and ________ ions are required for the synthesis of mRNA.
RNA polymerase, magnesium or manganese
Define the law of mass action.
When a reaction is at equilibrium, the ratio of the substrates to the products is always the same because reaction rate is constant.
During the synthesis of proteins, amino acids are assembled in the proper sequence because the tRNA molecules that bring them to the ribosome have a(n) ________ that is complementary to a specific codon in the mRNA.
anticodon
enzyme: dehydratase
class: hydrolase
enzyme: lipase
class: hydrolase
enzyme: synthetase
class: ligase
enzyme: aminase
class: lyase
enzyme: deaminase
class: lyase
enzyme: dehydrogenase
class: oxidoreductase
enzyme: kinase
class: transferase
Genes that are always being expressed in a cell involve promoters that are ________.
constitutively active
Metabolic intermediates use ________ bonds to transfer energy to the high-energy bonds of ATP, NADH, FADH2 or NADPH.
covalent
The peptide bond formed between amino acids occurs as a consequence of ________.
dehydration synthesis
Chemical reactions that require an input of energy are said to be ________.
endergonic
CARBONIC ANHYDRASE CO2 + H2O ---> H2CO3 role of: carbonic anhydrase
enzyme
The rates of chemical reactions that occur in the human body are controlled by a particular type of proteins called ________.
enzymes
Chemical reactions that release energy are said to be ________.
exergonic
The ________ contains the coding sequence of the gene.
exon
The ________ is the portion of the mRNA that contains the coding sequence of the gene.
exon
Glucose is phosphorylated to ________ with a phosphate from ________.
glucose-6-phosphate, ATP
The electron transport system is located in the ________ and includes enzymes and iron-containing proteins known as ________.
inner mitochondrial membrane, cytochromes
A certain molecule that participates in more than one biochemical pathway and acts as a branch point for channeling substrate in one direction or another is called a ________.
key intermediate
A molecule of ________ consists of all the codons needed to produce a specific polypeptide chain at the ribosome.
mRNA
Protein folding can take place spontaneously or with ________.
molecular chaperones
The availability of ________ determines if pyruvate continues into the citric acid cycle.
oxygen
In the process of ________ a phosphate group is attached to a molecule.
phosphorylation
A molecule positioned on the high-concentration side of a concentration gradient stores ________ energy.
potential
Energy released by electrons moving through the electron transport system is stored as ________ by H+ ions concentrated in the ________.
potential energy, intermembrane space
CARBONIC ANHYDRASE CO2 + H2O ---> H2CO3 role of: H2CO3
product(s)
Transcription factors are proteins whose binding to the ________ region for a gene can ________ (increase) or ________ (decrease) expression of that gene.
promoter, induce, repress
Ribosomes are composed of protein and ________.
rRNA
A chemical reaction that can proceed in both directions is called a ________ reaction.
reversible
RNA is usually ________ -stranded.
single
CARBONIC ANHYDRASE CO2 + H2O ---> H2CO3 role of: CO2 + H2O
substrate(s)
Amino acids are carried to the ribosomes to be incorporated into polypeptide chains by ________.
tRNA
mRNA is created in a process called ________. It then leaves the ________ and enters the cytosol to direct ________, the assembly of amino acids into protein.
transcription, nucleus, translation