Physiology Chapter 4 Exam
37) ATP synthase transfers the ________ energy of the H+ ions to the high-energy phosphate bond of ________.
D) kinetic, ATP
68) ________ describes how much product is generated or substrate destroyed within a period of time.
Reaction rate
Cells normally regulate the rate of an enzymatic reaction by
B) changing the concentration of an enzyme.
67) 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
78) Amino acids are carried to the ribosomes to be incorporated into polypeptide chains by ________.
: tRNA
107) 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.
17) An allosteric modulator binds to
A) a region of the enzyme other than the active site.
20) An enzyme that adds or subtracts water molecules is a
A) hydrolase.
44) Transcription occurs in the ________ of the cell.
A) nucleus
38) An example of transamination is
A) removing an amine group from one molecule and binding it to a different molecule.
41) The TAC sequence of DNA is the ________ of a coding sequence that is preceded by the ________ that regulates transcription.
A) start, promoter region
10) When a chemical reaction is in equilibrium,
A) there is no net change in the amount of substrates or products.
59) carbonic anhydrase
A. enzyme
Match the specific enzyme to its class. 52) dehydrogenase
A. oxidoreductase
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.
71) The activity of metabolic pathways is influenced by the ratio of ________.
ATP to ADP
65) Metabolic intermediates use ________ bonds to transfer energy to the high-energy bonds of ATP, NADH, FADH2 or NADPH.
Answer: covalent
63) Chemical reactions that require an input of energy are said to be ________.
Answer: endergonic
66) The rates of chemical reactions that occur in the human body are controlled by a particular type of proteins called ________.
Answer: enzymes
64) Chemical reactions that release energy are said to be ________.
Answer: exergonic
61) A molecule positioned on the high-concentration side of a concentration gradient stores ________ energy.
Answer: potential
62) A chemical reaction that can proceed in both directions is called a ________.
Answer: reversible reaction
34) What is the potential yield of ATP molecules for each FADH2 molecule entering the electron transport system?
B) 1.5
27) 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?
B) DNA
45) The enzymes that synthesize mRNA from the start codon are called
B) RNA polymerases.
35) Why is there a range of 30-32 ATP molecules produced from one glucose molecule
B) The NADH molecules produced during glycolysis are in the cytoplasm; occasionally, electrons are carried by the lower energy FADH2 instead of NADH.
101) In order to slow generation of product from a particular biochemical pathway within a cell, the intermediates formed by that pathway
B) accumulate inside the cell.
42) All of the triplet codes needed to produce exactly one functional piece of RNA are found in one
B) gene.
28) Compartmentation refers to
B) grouping related enzymes into specific organelles.
22) A molecule that loses electrons during a reaction is
B) oxidized.
31) In the aerobic metabolism of glucose, ________ acts as the final electron acceptor.
B) oxygen
Which of the following is a key intermediate of glucose catabolism to the citric acid cycle?
B) pyruvate
23) The active sites of enzymes are
B) regions of an enzyme that are involved in bringing substrates together.
16) A competitive inhibitor binds to
B) the active site.
39) The process of forming mRNA is called
B) transcription.
117) Explain how these statements differ, and identify which one(s) is/are correct. Explain what is wrong with each incorrect statement.
B. A chemical reaction is at equilibrium when the amounts of substrates and product no longer change 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.
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.
B. A chemical reaction proceeds until the substrate molecules are all consumed. C. A chemical reaction proceeds until equilibrium is established : 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.
Match the specific enzyme to its class. 53) dehydratase
B. hydrolase
Match the specific enzyme to its class. 54) lipase
B. hydrolase
58) CO2 + H2O
B. substrate(s)
103) The net energy yield for the anaerobic metabolism of one glucose molecule is
C) 2 ATP and 0 NADH.
33) For each NADH molecule that moves through the electron transport system, what is the potential yield of ATP molecules?
C) 2.5
108) What happens to the oxygen that is metabolized within the mitochondria?
C) The oxygen is combined with hydrogen to form water.
11) Organic molecules that act as receptors/carriers for the cleaved portion of the substrate are
C) coenzymes.
30) The reactions of glycolysis occur in the cell's ________; the reactions of the citric acid cycle occur in the ________.
C) cytoplasm, mitochondria
106) Oxidative phosphorylation occurs ________; the beneficial end product is ________.
C) in the mitochondria due to the electron transport system, ATP
12) The activity of an enzyme is changed by environmental factors such as temperature or pH; these factors are referred to as
C) modulators.
43) Information stored in the nucleus is translated into
C) proteins.
104) Inside the matrix of the mitochondria, pyruvate
C) requires the vitamin pantothenic acid for its conversion to acetyl CoA.
24) 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
C) saturation.
Activation energy is
C) the energy required to bring molecules into a position where they can interact.
18) An enzyme that transfers chemical groups among substrates is a
C) transferase.
60) H2CO3
C. product(s)
Match the specific enzyme to its class. 55) kinase
C. transferase
105) NADH is produced from each reaction described except one. Identify the exception.
D) during anaerobic glycolysis
25) Which of these results in a REDUCED molecule?
D) gain of electrons
26) End-product inhibition describes the process whereby
D) increasing amounts of product reduce activity of the enzyme.
19) An enzyme that joins two substrates using energy is a
D) ligase.
13) The addition of a phosphate group to a substrate is called ________. The enzyme that catalyzes this reaction is referred to as a ________.
D) phosphorylation; kinase
29) Aerobic metabolism of glucose
D) requires oxygen and produces more ATP per glucose than anaerobic pathways.
5) The ________ of glycogen from many glucose molecules is an ________ reaction.
D) synthesis, endergonic
40) After forming a complex with the ribosome, mRNA interacts with a third molecule. This molecule is called
D) tRNA.
32) The explanation for how ATP bonds are actually formed during oxidative phosphorylation is called
D) the chemiosmotic theory.
4) Chemical reactions in a living system function to
D) transfer energy from one molecule to another or use energy stored in a molecule.
Match the specific enzyme to its class. 51) synthetase
D. ligase
Enzymes are often useful as diagnostic tools. How?
Damaged cells release enzymes into the blood that can be detected.
14) Phosphate groups may be transferred from one molecule to another during
E) addition and exchange reactions.
15) When an enzyme's activity is destroyed by heat or a change in pH, the enzyme is said to be
E) denatured.
36) Which can serve as substrates for ATP production?
E) glucose, amino acids and fatty acids
21) An enzyme that transfers phosphates from ATP to a substrate molecule is a
E) kinase
56) aminase
E. lyase
57) deaminase
E. lyase
73) ________ generated in the ________ enter the electron transport system to generate 2.5 ATP
NADH, mitochondria
116) 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.
79) The enzyme ________ and ________ ions are required for the synthesis of mRNA.
RNA polymerase, magnesium or manganese
How would the lack of a required cofactor for an enzyme affect that enzyme's function?
The enzyme would not be able to function.
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.
The rate of product formation by an enzyme-catalyzed reaction would be increased by
adding more substrate molecules.
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
8) Isozymes
are enzymes with slightly different structure that catalyze the same reaction.
Changes in environmental pH or temperature will cause the reaction rate for an enzyme to
either increase or decrease depending upon enzyme properties.
70) Glucose is phosphorylated to ________ with a phosphate from ________.
glucose-6-phosphate, ATP
75) The electron transport system is located in the ________ and includes enzymes and iron-containing proteins known as ________.
inner mitochondrial membrane, cytochromes
9) Enzymes increase reaction rate by
lowering the activation energy of a reaction.
80) A molecule of ________ consists of all the codons needed to produce a specific polypeptide chain at the ribosome.
mRNA
69) The availability of ________ determines if pyruvate continues into the citric acid cycle.
oxygen
72) In the process of ________ a phosphate group is attached to a molecule.
phosphorylation
74) Energy released by electrons moving through the electron transport system is stored as ________ by H+ ions concentrated in the ________.
potential energy, intermembrane space
The general term that describes energy stored in chemical bonds is
potential energy.
81) Ribosomes are composed of protein and ________.
rRNA
An exergonic chemical reaction
releases energy as the reaction progresses
82) RNA is usually ________ -stranded.
single
83) Two types of RNA block translation of mRNA. They are ________ RNA and ________ RNA.
small interfering, micro
According to the second law of thermodynamics,
the amount of entropy in living systems increases without the input of energy.
1) Energy is defined as
the capacity to do work
7) A reversible reaction is one where
there are small changes in the net free energy from substrate to product.
77) 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
119) Consider the two chemical reactions. Identify each statement following as true or false, and clarify as needed. A + B → C C → A + B A. The enzyme catalyzing the formation of C must be different from that catalyzing the breakdown of C. B. The enzyme catalyzing the formation of C must be the same as that catalyzing the breakdown of C. C. Only one of the reactions could occur in a given cell or system. D. Both reactions must be occurring in an equilibrium situation. E. Equilibrium is always achieved in a chemical reaction. F. Equilibrium can be prevented from occurring by constantly removing the product of either reaction. G. An equilibrium, once established, cannot be disturbed. Answer: A. False. There may be more than one enzyme for the reactions listed, but a given enzyme is often capable of performing a reaction in both directions. B. False. The enzyme for both reactions could be the same, but often a particular enzyme is more likely to perform the forward reaction while a different enzyme is more likely to perform the reverse. C. False. If the reactions are at equilibrium, both are occurring at the same time. If they are not at equilibrium, it is possible that the reaction is occurring only in one direction. In addition, cells can have different enzymes for each reaction direction that can be differentially controlled (i.e., one active and the other inactive). D. True. By definition, a reaction is at equilibrium when both directions are occurring such that there is no net change in amounts of substrates and products. E. False. Equilibrium is not necessarily established, especially in a cell where a product is immediately removed from the system for use elsewhere, such as the product ATP, or if a given enzyme does not perform the reverse reaction. F. True. Any change in amounts of enzyme, substrate, or product will disturb equilibrium, and if these things constantly change, equilibrium cannot be established. G. False. Equilibrium can be disturbed by changing the amount of enzyme, substrate, or product, or by altering the enzyme's efficacy by changing temperature or pH.
true or false