Mastering Chapter 8: Intro to Metabolism
As a result of its involvement in a reaction, an enzyme...
...is unchanged.
Most cells cannot harness hear to perform work because...
...temperature is usually uniform throughout a cell.
In this reaction...
...the produces have less potential energy than the reactants. Entropy always increases.
What is the fate of the phosphate group that is removed when ATP is converted to ADP?
It is acquired by a reactant in an endergonic reaction.
An enzyme is considered a ______________ because it speeds up chemical reactions without being used up.
catalyst
Chemical energy is a form of ______________ energy.
potential
Enzyme inhibitors disrupt normal interactions between an enzyme and its ______________.
substrate
In a catalyzed reaction a reactant is often called a ________________.
substrate
Select the INCORRECT association.
Exergonic...uphill
A chemical reaction occurs between the amino acids alanine (Ala) and glycine (Gly), forming the compound alanylglycine. The simple conversion reaction of alanine and glycine into this compound is endergonic, with a ΔG of 6.9 kcal/mol. Therefore, it requires ATP hydrolysis to drive the nonspontaneous reaction. Calculate the free energy change for the whole process, applying what you know about ATP hydrolysis.
ΔG = -0.4 kcal/mol
An enzyme-catalyzed reaction has a ΔG of -20 kcal/mol under standard conditions. What will be the ΔG for the reaction if the amount of enzyme is doubled?
-20 kcal/mol
The ΔG of ATP hydrolysis in a test tube under standard conditions is -7.3 kcal/mol. The ΔG for the reaction A + B = C under the same conditions is +4.0 kcal/mol. What is the overall free-energy change for the coupled reactions under these conditions?
-3.3 kcal/mol
The process of cellular respiration, which converts simple sugars such as glucose into CO2 ad water, is an example of...
...a catabolic pathway.
If an enzyme in solution is saturated with substrate, the most effective way to obtain a faster yield of products is to...
...add more of the enzyme.
A series of enzymes catalyze the reactions in the metabolic pathway X →→ Y →→ Z →→ A. Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme. Based on its interaction with the enzyme that converts X to Y substance A is best described as...
...an allosteric inhibitor.
Conservation of energy refers to the fact that...
...energy cannot be created r destroyed but can be converted from one form to another.
In this reaction...
...heat has been released to the environment.
Enzyme are described as catalysts, which means that they...
...increase the rate of a reaction without being consumed by the reaction.
An enzyme...
...is an organic catalyst because it contains carbon.
Which of these is ATP?
3 Phosphate groups attached to a Ribose attached to Adenine
Disruption of the active site of an enzyme would most likely results in which of the following?
A decreased ability of the enzyme to bind substrates.
Which of the following statements about equilibrium of chemical reactions is correct?
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 is an example of kinetic video? a. the high energy phosphate bonds of a molecule of ATP. b. a rock on a mountain ledge. c. a person sitting on a couch while watching tv. d. an archer with a flexed bow. e. a space station orbiting Earth.
A space station orbiting Earth
In cells, what is usually the immediate source of energy for an endergonic reaction?
ATP
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?
Add more substrate; it will outcompete the inhibitor and increase the reaction rate.
Which of the following statements best describes induced fit?
Binding of substrate to the active site changes the shape of the active site of an enzyme.
N2(g)+3H2(g)⇌2NH3(g)N2(g)+3H2(g)⇌2NH3(g) What will happen to the rates of the forward and reverse reactions when a catalyst is added?
Both forwards and reverse rates increase. The Haber process can be cheaply catalyzed using porous iron. A much more effective catalyst for the Haber process is osmium; however, it is very expensive and toxic.
How does a noncompetitive inhibitor decrease the rate of an enzyme catalyzed reaction?
By binding to an allosteric site, thus changing the shape of the active site of the enzyme.
Which of these reactions requires a net input of energy from its surroundings?
Catabolic
In your body, what process converts the chemical energy found in glucose into the chemical energy found in ATP?
Cellular respiration
Which temperature and pH profile curves on the graphs are most likely associated with an enzyme isolated from a human stomach where conditions are strongly acidic?
Curves 1 and 4
Which of the following terms best describes a chemical reaction for which ΔG is positive?
Endergonic
What is the correct label for A?
Energy of activation
What are the by-products of cellular respiration?
Heat, carbon dioxide, and water.
What type of reaction breaks the bonds that join the phosphate groups in an ATP molecule?
Hydrolysis
Consider a situation in which the enzyme is operating at optimum temperature and pH, and has bee saturated with substrate. What is your best option for increasing the rate of reaction?
Increase the enzyme concentration
N2(g)+3H2(g)⇌2NH3(g)N2(g)+3H2(g)⇌2NH3(g) Which of the following would increase the rate of the reverse reaction?
Increasing the concentration of ammonia. The concentration of NH3NH3 affects how quickly N2N2 and H2H2 can be made.
When chemical, transport, or mechanical work is performed by an organism, what happens to the heat that is generated?
It is lost to the environment.
When ATP is hydrolyzed to activate a target protein, what is often the fate of the inorganic phosphate that is released?
It may be use to form phosphorylated intermediate.
Select the correct statement about chemical energy, a term used by biologists to refer to potential energy available for release in a chemical reaction.
Light energy is converted to chemical energy during photosynthesis
Which of the following statements best describes metabolism in it entirety in all organisms?
Metabolism consists of all the energy transformation reactions in an organism.
Which has the highest energy form of adenosine?
Nitrogen, sugar base, and three phosphates. Contains the most phosphate groups so it is the most energetic.
Energy is observed in two basic forms: potential and kinetic. Which of the following correctly matches these forms with a source of energy?
Potential energy with the covalent bonds of a sugar molecule.
In general, enzymes are what kinds of molecules?
Proteins
In which region does the reaction rate remain constant?
Region C
In which region is the enzyme saturated with substrate?
Region C
What name is given to the reactants in an enzymatically catalyzed reaction?
Substrates
Which part of the adenosine triphosphate molecule is released when it is hydrolyzed to provide energy for biological reactions.
Terminal phosphate
How does the phosphorylation of glutamic acid (Glu) provide energy for the rest of the reaction to occur?
The addition of phosphate to the Glu forms a phosphorylated intermediate with more free energy than Glu. The ammonia can thus displace the phosphate in an exergonic reaction. Without the input of free energy from ATP, Glu would not spontaneously react with ammonia and form glutamine. ATP hydrolysis removes the terminal phosphate of the ATP molecule. This phosphate bonds to Glu, forming what's called the phosphorylated intermediate. The phosphorylation of Glu increases the free energy of the reactant so that the rest of the reaction can proceed spontaneously in an exergonic fashion.
Which of the following is NOT a way in which an enzyme can speed up the reaction that it catalyzes?
The active site can provide heat from the environment that raises the nerf content of the substrate. An enzyme cannot extract heat from the environment to speed a reaction.; it can only lower the activation energy barrier so that more substrates have the energy to react.
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?
The enzyme is inactive at this point. New enzyme must be added to regain enzyme activity.
Which of the following statements best describes an exergonic reaction?
The reaction proceeds with a net release of free energy.
N2(g)+3H2(g)⇌2NH3(g)N2(g)+3H2(g)⇌2NH3(g) What would happen to the rate of the forward section is the concentration of nitrogen were decreased?
The reaction rate would decrease.
The Haber process is typically carried out at a temperature of approximately 500∘C∘C. What would happen to the rate of the forward reaction if the temperature were lowered to 100∘C∘C?
The reaction rate would decrease.
What is energy coupling?
The use of energy released from an exergonic reaction to drive an endergonic reaction.
Which of the following statements best describes catabolic pathways?
They are exergonic and provide energy that can be used to produce ATO from ADP and Pi.
Place the reaction rates in order of lowest reaction rate to highest reaction rate.
Uncatalyzed reaction, reaction catalyzed by enzyme A, and reaction catalyzed by enzyme B.
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
A ____________, such as a vitamin, binds to an enzyme and plays a role in catalysis.
cofactor
A (n) _____________ inhibitor has a structure that is so similar to the substrate that it can bond to the enzyme just like the substrate.
competitive
When properly aligned, the enzyme and substrate form an enzyme-substrate (ES) ______________.
complex
A decrease in entropy is associated with which of the following types of reaction? a. hydrolysis b. catabolic c. dehydration d. depolymerization
dehydration
An enzyme is ____________ when it loses its native conformation and its biological activity.
denatured
A reaction that occurs nonspontaneously - it requires an input of energy - is ______________.
endergonic
The reaction ADP + P --> ATP is a(n) __________ reaction.
endergonic
This graph illustrates a(n) ___________ reaction.
endergonic
A cell can only carry out an _______________ reaction by pairing it with an ______________ reaction, such as ATP hydrolysis.
endergonic; exergonic
When the noncompetitive inhibitor is bonded to the enzyme, the shape of the _____________ is distorted.
enzyme
A reaction that occurs spontaneously - without an input of energy - is ______________.
exergonic
A(n) ________________ reaction occurs spontaneously.
exergonic
The energy for an endergonic reaction comes from a(n) ________________ reaction.
exergonic
The following reaction A --> B + C + heat is a(n) ____________ reaction.
exergonic
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
Exergonic reactions result in products that have less free energy than the reactants, thus free energy is released and ΔG is _________________.
negative
A (n) ______________ inhibitor binds to a site on the enzyme that is not the active site.
noncompetitive
Endergonic reactions result in products that have more free energy than the reactants, thus free energy is absorbed and ΔΔG is _________________.
positive
Enzymes work by...
reducing EA (activation energy)
An enzyme is considered _____________ because of its ability to recognize the shape of a particular molecule.
specific
