Chapter 6 Mastering Biology
Which of these is ATP
3 Phosphate groups attached to a Ribose attached to Adenine
As a result of its involvement in a reaction, an enzyme _____. A) Is unchanged B) Permanently alters its shape. C) Loses a phosphate group D) Is used up E) Loses energy
A
Enzymes work by _____. A) Reducing EA B) Increasing the potential energy difference between reactant and product C) Adding a phosphate group to a reactant D) Decreasing the potential energy difference between reactant and product E) Adding energy to a reaction
A
Some bacteria are metabolically active in hot springs because __________. A. their enzymes have high optimal temperatures B. they use molecules other than proteins or RNAs as their main catalysts C. they are able to maintain a lower internal temperature D. high temperatures make catalysis unnecessary E. their enzymes are completely insensitive to temperature
A
Which of these are by-products of cellular respiration? A. heat, carbon dioxide, and water B. glucose, carbon dioxide, and water C. ATP and carbon dioxide D. Carbon dioxide and water E. ATP, carbon dioxide, and water
A
Which of the following statements about equilibrium of chemical reactions is correct? A.A reaction that is at equilibrium is not capable of doing any work. B.Reactions can only go in the direction toward equilibrium. C.The equilibrium point is where the system has the highest free energy D.Most reactions in a living cell are close to equilibrium. E.The equilibrium point of a reaction represents the least stable configuration for that reaction.
A. A reaction that is at equilibrium is not capable of doing any work. The ΔG for a reaction at equilibrium is zero, which means that there is no free energy available to do any work.
Which of the following statements about the combustion of glucose with oxygen to form water and carbon dioxide (C6H12O6 + 6 O2 → 6 CO2 + 6 H2O) is correct? A.The entropy of the products is greater than the entropy of the reactants. B.The entropy of the universe decreases as the result of this reaction. C.The free energy lost in this combustion is less than the energy that appears as heat. D.The reverse reaction, making glucose from water and carbon dioxide, must be an exergonic reaction. E.This is the process of cellular respiration, an anabolic pathway that releases free energy.
A. The entropy of the products is greater than the entropy of the reactants.
Choose the pair of terms that correctly completes this sentence: Catabolism is to anabolism as ______ is to _______. A. exergonic; spontaneous B. exergonic; endergonic C. free energy; entropy D. work; energy E. entropy; enthalpy
B
Select the INCORRECT association. A) exergonic ... spontaneous B) exergonic ... uphill C) kinetic energy ... motion D) enzyme ... protein E) potential energy ... positional energy
B
Select the correct statement about chemical energy, a term used by biologists to refer to potential energy available for release in a chemical reaction. A-A photosynthetic cell within a plant leaf produces chemical energy, stored within glucose molecules. B-Light energy is converted to chemical energy during photosynthesis. C-When a glucose molecule is catabolized to CO2 and H2O, chemical energy is lost
B
What is energy coupling? A) a barrier to the initiation of a reaction B) the use of energy released from an exergonic reaction to drive an endergonic reaction C) the hydrolysis of ATP to ADP + P D) the use of an enzyme to reduce EA E) a description of the energetic relationship between the reactants and products in an exergonic reaction
B
What is the correct label for "A"? A) ATP B) Energy of activation C) Substrate energy D) Uphill E) Enzyme energy
B
Which of the following is NOT a way in which an enzyme can speed up the reaction that it catalyzes? A.Binding of the substrate to the active site can stretch bonds in the substrate that need to be broken. B.The active site can provide heat from the environment that raises the energy content of the substrate. C.The binding of two substrates in the active site provides the correct orientation for them to react to form a product. D.The enzyme binds a cofactor that interacts with the substrate to facilitate the reaction. E.The active site of the enzyme can provide a microenvironment with a different pH that facilitates the reaction.
B
You have added an irreversible inhibitor to a sample of enzyme and substrate. At this point, the reaction has stopped completely.What can you do to regain the activity of the enzyme? A. Removing the irreversible inhibitor should get the reaction working again. B. The enzyme is inactive at this point. New enzyme must be added to regain enzyme activity. C. Adding more substrate will increase the rate of reaction. D. Adding more inhibitor should get the reaction up to speed again.
B
You have an enzymatic reaction proceeding at the optimum pH and optimum temperature. You add a competitive inhibitor to the reaction and notice that the reaction slows down.What can you do to speed the reaction up again? A. Add more inhibitor to speed up the reaction. B. Add more substrate; it will outcompete the inhibitor and increase the reaction rate. C. Increase the temperature. D. Increase the pH.
B
In general, enzymes are what kinds of molecules? A) Minerals B) Lipids C) Carbohydrates D) Proteins E) Nucleic acids
D
An enzyme _____. A) Is a inorganic catalyst B) Is a source of energy for endergonic reactions C) Is an organic catalyst D) Can bind to nearly any molecule E) Increases the EA of a reaction
C
"Conservation of energy" refers to the fact that _____. A.if you conserve energy you will not be as tired B.no chemical reaction is 100 percent efficient C.the net amount of disorder is always increasing D.the entropy of the universe is always increasing E.energy cannot be created or destroyed but can be converted from one form to another
E
What name is given to the reactants in an enzymatically catalyzed reaction? A) Products B) Active sites C) Substrate D) EA E) Reactors
C
Which part of the adenosine triphosphate molecule is released when it is hydrolyzed to provide energy for biological reactions? A. α -phosphate (the phosphate closest to ribose) B. β-phosphate (the middle phosphate) C.γ-phosphate (the terminal phosphate) D.adenine group E.ribose sugar
C
Which reaction would prevail if both Q and S were present in the cell in high concentrations? A.L→→M B.M→→O C.L→→N D.O→→P
C
Energy is observed in two basic forms: potential and kinetic. Which of the following correctly matches these forms with a source of energy?A. the energy related to the height of a bird above the ground: kinetic energy B.the energy associated with a gradient of ions across a membrane: kinetic energy C.the covalent bonds of a sugar molecule: potential energy D.the motion of individual molecules: potential energy E.the heat released from a living organism: potential energy
C. the covalent bonds of a sugar molecule: potential energy. Bonds are a form of potential energy because the energy arises from the relative positions of the atoms that form the bond.
In your body, what process converts the chemical energy found in glucose into the chemical energy found in ATP? anabolism cellular respiration potentiation redox digestion
Cellular respiration
Most cells cannot harness heat to perform work because a. cells do not have much heat; they are relatively cool. b. heat must remain constant during work. c. heat is not a form of energy. d. temperature is usually uniform throughout a cell. e. heat can never be used to do work.
D
The binding of a compound to an enzyme is observed to slow down or stop the rate of the reaction catalyzed by the enzyme. Increasing the substrate concentration reduces the inhibitory effects of this compound. Which of the following could account for this observation? A.The compound is an allosteric inhibitor. B.The compound forms a covalent bond with one of the amino acid residues needed for enzyme activity. C.The compound causes a cofactor to be lost from the enzyme. D.The compound is a competitive inhibitor. E.The compound reduces disulfide bonds, causing the enzyme molecules to partially unfold.
D
Which of these is exhibiting kinetic energy? A.an archer with a flexed bow B.the high-energy phosphate bonds of a molecule of ATP C.a person sitting on a couch while watching TV D.a space station orbiting Earth E.a rock on a mountain ledge
D
The process of cellular respiration, which converts simple sugars such as glucose into CO2 and water, is an example of __________ A..a pathway that converts organic matter into energy B.a pathway in which the entropy of the system decreases C.a pathway that occurs in animal cells but not plant cells D.a catabolic pathway E.an endergonic pathway
D. catabolic pathway
The Haber process is typically carried out at a temperature of approximately 500. What would happen to the rate of the forward reaction if the temperature were lowered to 100? The reaction rate would increase. The reaction rate would not change. The reaction rate would decrease.
DECREASE
What is the free energy change (ΔG) of the hydrolysis of ATP to ADP?A-The free-energy change (ΔG) of the hydrolysis of ATP to ADP and Pi is approximately B-7.3 kcal/mole, but it varies from species to species. C-In living cells, conditions always conform to standard conditions and the free-energy change (ΔG) of the hydrolysis of ATP to ADP and Pi is -7.3 kcal/mole. D-The free-energy change (ΔG) of the hydrolysis of ATP to ADP and Pi is constant at -7.3 kcal/mole. E-The free-energy change (ΔG) of the hydrolysis of ATP to ADP and Pi may vary considerably with variations in pH, temperature, atmospheric pressure, and concentrations of reactants and products.
E
Consider a situation in which the enzyme is operating at optimum temperature and pHpH, and has been saturated with substrate. What is your best option for increasing the rate of the reaction? Increase the pH. Increase the temperature. Increase the enzyme concentration. Increase the substrate concentration.
Increase the enzyme concentration ----- If an enzyme is saturated with substrate, and it is operating at optimum pH and optimum temperature, there is very little that can be done except to increase the enzyme concentration. Some enzymes can be activated further by allosteric activators, in which case one might add some activator to the reaction. But otherwise, increasing the enzyme concentration is the only option.
Which of the following statements is most likely to be true in the case of the feedback-regulated enzymatic pathway shown?
P4 binds E1 and deactivates it. > Many enzymatic pathways are regulated by the feedback inhibition model described here. In fact, it is so common that another name for it is end-product inhibition.
Refer again to the graph. In which region is the enzyme saturated with substrate?
REGION C
In general, an enzyme has one active site at which catalysis can occur. When the substrates are bound to the active site, the enzyme will catalyze the reaction. As the concentration of substrate increases, the reaction rate increases, until the point where the active site is saturated with substrate. When the enzyme is saturated, the rate of the reaction will not increase with the concentration of substrates. Look at the graph of reaction rate versus substrate concentration for an enzyme. In which region does the reaction rate remain constant? A B C
Region C
Complete a model to explain the molecular events occurring at each stage of this reaction profile.
SECTION A:The substrate moleculesare entering the cells,so no product is madeyet. SECTION B:There is sufficientsubstrate, so the reactionis proceeding at amaximum rate. SECTION C:As the substrate is usedup, the rate decreases(the slope is less steep) SECTION D:The line is flat becauseno new substrate remainsand thus no new productappears.
How does an enzyme increase the rate of the chemical reaction it catalyzes? a. An enzyme reduces the free-energy change (ΔG) of the reaction it catalyzes. b. An enzyme's active site binds only the reactants, and not the products of a reaction, pushing the equilibrium for the reaction far to the right. c.An enzyme reduces the free energy of activation (EA) of the reaction it catalyzes.
a
If an enzyme in solution is saturated with substrate, the most effective way to obtain a faster yield of products is to a. add more of the enzyme. b.add more substrate. c,add a noncompetitive inhibitor. d.add an allosteric inhibitor. e.heat the solution to 90°C.
a
The reaction ADP + P --> ATP is a(n) _____ reaction. A) endergonic B) spontaneous C) exergonic D) hydrolysis E) chemical
a
Which of the following statements about the role of ATP in cell metabolism is true? a- The energy from the hydrolysis of ATP may be directly coupled to endergonic processes by the transfer of the phosphate group to another molecule b-The free energy released by ATP hydrolysis has a much more negative ΔG value than the hydrolysis of phosphate groups from other phosphorylated molecules. c-The phosphate bonds of ATP are unusually strong bonds.
a
Which of the following would increase the rate of the reverse reaction? a.increasing the concentration of ammonia b.decreasing the temperature c.increasing the concentration of nitrogen
a
6. A substrate binds to an enzyme at the ________ _______, where the reaction occurs.
active site
The competitive inhibitor competes with the substrate for the _____ _______ on the enzyme.
active site
In this reaction a. AC is a reactant b.the products have less potential energy than the reactants c. CD is a product d.the products have been rearranged to form reactants e.entropy has decreased
b
What will happen to the rates of the forward and reverse reactions when a catalyst is added? a.Forward rate increases; reverse rate decreases. b.Both forward and reverse rates increase. c.Both forward and reverse rates decrease. d.Forward rate decreases; reverse rate increases.
b
Which of the following statements about ATP (adenosine triphosphate) is correct? a.The hydrolysis of ATP is an endergonic process. b.The cycling between ATP and ADP + Pi provides an energy coupling between catabolic and anabolic pathways. c.The energy release on hydrolysis of ATP is the result of breaking a high-energy bond. d.The hydrolysis of ATP can supply energy needed for catabolic pathways. e.eAlmost all of the free energy released on the hydrolysis of ATP is released as heat.
b
Which of the following metabolic processes can occur without a net influx of energy from some other process? a. ADP+P-->ATP+H2o b. C6H12O6+ 6O2-->6CO2+6H2O c. 6CO2+6H2O-->C6H12O6+6O2 d. amino acids--> sucrosee. glucose+fructose-->sucrose
b. C6H12O6+ 6O2-->6CO2+6H2O
What type of reaction breaks the bonds that join the phosphate groups in an ATP molecule? a.dehydration synthesis b. dehydration decomposition c.hydrolysis d. anabolism e. entropic
c
Which statement about the binding of enzymes and substrates is correct? a.Substrate molecules fit into the active site of an enzyme like a key fits into a lock. b.Substrate molecules bind to the active site of the enzyme only by weak bonds, such as hydrogen bonds or hydrophobic attraction. c.When substrate molecules bind to the active site of the enzyme, the enzyme undergoes a slight change in shape.
c
An enzyme is considered a _________-because it speeds up chemical reactions without being used up.
catalyst
A ____________-, such as a vitamin, binds to an enzyme and plays a role in catalysis.
cofactor
1. A (n)_____________inhibitor has a structure that is so similar to the substrate that it can bond to the enzyme just like the substrate.
competetive
When properly aligned, the enzyme and substrate form an enzyme-substrate (ES)________
complex
Enzymes are described as catalysts, which means that they _____. a. increase the free energy of the reactants to make the reaction go faster b. provide activation energy for the reactions they facilitate c. can alter the free energy change (ΔG) for a chemical reaction d. increase the rate of a reaction without being consumed by the reaction e. are proteins
d
If an enzyme is added to a solution where its substrate and product are in equilibrium, what will occur? a. Additional product will be formed. b. The free energy of the system will change. c. Additional substrate will be formed. d. Nothing; the reaction will stay at equilibrium. e. The reaction will change from endergonic to exergonic.
d
In this reaction a.disorder has decreased b.entropy has decreased c.the chemical energy of the products is greater than that of the reactants d.heat has been released to the environment e.the kinetic energy of the reactants is less than that of the products
d
The energy for an endergonic reaction comes from a(n) _____ reaction. A) glucose + glucose --> maltose B) ADP + P --> ATP C) anabolic D) exergonic E) synthesis
d
The graph illustrates a(n) _____ reaction (Reactants have less energy than products) A) spontaneous B) hydrolysis C) exergonic D) endergonic E) catabolic
d
The type of enzymatic regulation in which a substrate molecule binds to an enyzme thereby enhancing the catalytic activity of that enzyme is called a.cooperativity b.catalysis c.activation energy d.allosteric activation e.induced fit
d
What is the fate of the phosphate group that is removed when ATP is converted to ADP? A) It is used to convert an ATP into an AQP. B) It is acquired by a reactant in an exergonic reaction. C) It is acquired by a reactant in a spontaneous reaction. D) It is acquired by a reactant in an endergonic reaction. E) It is broken down into one phosphorus and four oxygen atoms.
d
Which of the following would be unlikely to contribute to the substrate specificity of an enzyme? a. The enzyme has the ability to change its configuration in response to the substrate binding. b. A hydrophobic group on the substrate interacts with several hydrophobic amino acids on the enzyme. c. A similar shape exists between a pocket on the surface of the enzyme and a functional group on the substrate. d. Environmental factors such as temperature and pH. e. A positive charge on the substrate is attracted to a negative charge in the active site of the enzyme.
d
An enzyme is _____________when it loses its native conformation and its biological activity.
denatured
In cells, what is usually the immediate source of energy for an endergonic reaction? a. glucose b. as spontaneous reactions, endergonic reactions do not need an addition of energy c. ADP d. sugar e. ATP
e
Which of these reactions requires a net input of energy from its surroundings? a.hydrolysis b.exergonic c.endergonic d.ATP --> ADP + P e.catabolic
endergonic
When the noncompetitive inhibitor is bonded to the enzyme, the shape of the ________ is distorted.
enzyme
A(n) _____ reaction occurs spontaneously. endergonic anabolic kinetic exergonic chemical
exergonic
T The following reactionA --> B + C + heat is a(n) _____ reaction. endergonic exchange anabolic exergonic ehydration synthesis
exergonic
Select the highest energy form of adenosine from the following images. Adenosine triphosphate (ATP) is the high-energy form of adenosine because it contains the most phosphate groups (three). This molecule fuels many different endergonic (energy-requiring) enzymatic processes in biological organisms. ATP molecules diffuse or are transported to the place where the energy is needed and deliver chemical energy from the breaking of their phosphate bonds.
http://www.easynotecards.com/uploads/256/19/1a051c84_148803f3445__8000_00000510.jpg Adenosine triphosphate (ATP) is made up of three main structural parts: the nitrogenous base adenine, the ribose sugar, and the three phosphate groups bonded together by phosphodiester bonds
Usually, a(n) ____________ inhibitor forms a covalent bond with an amino acid side group within the active site, which prevents the substrate from entering the active site or prevents catalytic activity.
irreversible
The graph presents three activation energy profiles for a chemical reaction (the hydrolysis of sucrose): an uncatalyzed reaction, and the same reaction catalyzed by two different enzymes. Rank these by reaction rate, as measured by the rate of product formation per unit time, from lowest reaction rate to highest reaction rate. To rank items as equivalent, overlap them.
lowest to highest uncatalyzed reaction reaction catalyzed by enzyme A reaction catalyzed by enzyme B
A (n)__________________ inhibitor binds to a site on the enzyme that is not the active site.
noncompetitive
Chemical energy is a form of _____ energy. kinetic potential entropic heat motion
potiental
An enzyme is considered _____________-because of its ability to recognize the shape of a particular molecule.
specific
=In a catalyzed reaction a reactant is often called a _________
substrate
Enzyme inhibitors disrupt normal interactions between an enzyme and its ______________-
substrate
What would happen to the rate of the forward reaction if the concentration of nitrogen were decreased? The reaction rate would decrease. The reaction rate would increase. The reaction rate would not change.
the reaction rate will decrease
