Unit 2 (Week 5 Assignment Questions) Flashcards
Reactions that release free energy are
exergonic.
spontaneous.
endergonic.
endothermic.
both a and b.
E
Enzymes speed up reactions by
providing chemical energy to fuel a reaction.
lowering the activation energy necessary to initiate a reaction.
causing an endergonic reaction to become an exergonic reaction.
substituting for one of the reactants necessary for a reaction.
none of the above.
B
For the idealized reaction aA + bB ⇌ cC + dD, suppose that the equilibrium constant, Keq, is 0.01. If the starting concentrations for A, B, C, and D are 1 M each, what would you predict based on the value of Keq?
The forward reaction is favored.
The reverse reaction is favored.
The forward reaction is fast.
The reverse reaction is fast.
both b and d.
B
IF the EC is over 1.0, the reaction is forward. Less than 1, the reaction is favored in reverse.
Researchers analyzed a cell extract—a mixture of molecules isolated from a certain type of cell—and studied a chemical reaction in which a carbohydrate was broken down into smaller molecules. When they added a protease to the cell extract, they discovered that the protease greatly inhibited the rate of the reaction. Based on this observation, you could conclude that the reaction is
exergonic.
endergonic.
catalyzed by an enzyme.
catalyzed by a ribozyme.
Both b and c are true of this reaction.
C
In biological systems, ATP functions by
providing the energy to drive endergonic reactions.
acting as an enzyme and lowering the activation energy of certain reactions.
adjusting the pH of intracellular solutions to maintain optimal conditions for enzyme activity.
regulating the speed at which endergonic reactions proceed.
interacting with enzymes as a cofactor to stimulate chemical reactions.
A
In a chemical reaction, NADH is converted to NAD+ + H+. We say that NADH has been
reduced.
phosphorylated.
oxidized.
decarboxylated.
methylated.
C
Scientists identify proteins that use ATP as an energy source by
determining whether a protein functions in anabolic or catabolic reactions.
determining if a protein has a known ATP-binding site.
predicting the free energy necessary for a protein to function.
determining if a protein has an ATP synthase subunit.
all of the above.
B
For a particular chemical reaction, an inhibitor raises the KM but does not affect the Vmax. This inhibitor
is a competitive inhibitor.
is a noncompetitive inhibitor.
binds to the active site of the enzyme.
binds to an allosteric site of the enzyme.
is a competitive inhibitor and binds to the active site of the enzyme.
E
Which of the following is (are) key benefits of catabolic reactions?
recycling of organic building blocks
breakdown of organic molecules to obtain energy
synthesis of important polymers, such as polypeptides
all of the above
a and b only
E
With regard to rate and direction, discuss the differences between endergonic and exergonic reactions.
Exergonic reactions are spontaneous. They proceed in a particular direction. An exergonic reaction could be slow or fast. By comparison, an endergonic reaction is not spontaneous. It will not proceed in a particular direction unless free energy is supplied. An endergonic reaction can be fast or slow.
Describe the mechanism and purpose of feedback inhibition in a metabolic pathway.
During feedback inhibition, the product of a metabolic pathway binds to an allosteric site on an enzyme that acts earlier in the pathway. The product inhibits this enzyme, thereby preventing the overaccumulation of the product.
A core concept of biology is that living organisms use energy. Explain why the recycling of amino acids and nucleotides is energy-efficient.
Recycling of amino acids and nucleotides conserves a great deal of energy. Cells don’t have to remake these building blocks, which would require a large amount of energy.
Which of the following can take place during a chemical reaction?
Multiple select question.
The amount of matter increases.
Molecules are broken apart.
Electrons are transferred between atoms.
Molecules attach to each other to form larger molecules.
Rearrangements of atoms within molecules occur.
B, C, D, E
What are the two main factors that determine the outcome of a chemical reaction in a living cell?
Multiple choice question.
Direction and rate
Reactants and products
Energy and reactants
Direction and rate
What is the term for the ability to do work?
Multiple choice question.
Kinetic energy
ATP
Energy
Potential energy
Energy
Energy that is associated with movement is termed ___________ energy, while _________ is stored energy.
Kinetic and potential
Which of the following statements are true according to the second law of thermodynamics?
Multiple select question.
As disorder increases, entropy increases.
Energy can be transferred or transformed from one form to another.
The transformation of energy from one form to another increases the entropy of a system.
Energy is conserved when transferred from one form to another.
As disorder increases, entropy increases.
The transformation of energy from one form to another increases the entropy of a system.
One or more substances are changed or converted into other substances during _____ reactions.
Chemical
For living organisms, the total energy (H) is called
_________, while the free energy (G) is the amount available to do work.
Enthalpy
A chemical reaction that will proceed without the input of energy is a(n) ________ reaction.
Exergonic or spontaneous
Which of the following describes the major difference between kinetic and potential energy?
Multiple choice question.
Kinetic energy is the energy of motion and potential energy is associated with the position of an object.
Potential energy is the energy of motion and kinetic energy is associated with the position of an object.
Kinetic energy is stored in chemical bonds and potential energy is associated with the position of an object.
A
What equation is used to evaluate whether a chemical reaction is spontaneous?
Multiple choice question.
ΔG = ΔH - TΔS
ΔG = ΔH + TΔS
ΔG = ΔH - TΔS
The delta indicates change, such as before and after a chemical reaction.
These statements pertain to the first law of thermodynamics. Which of them are true?
Multiple select question.
Energy is conserved when transferred from one form to another.
As disorder increases, entropy increases.
Energy can be transferred or transformed from one form to another.
The transformation of energy from one form to another increases the entropy of a system.
Energy is conserved when transferred from one form to another.
Energy can be transferred or transformed from one form to another.
What type of reaction results in products that contain less free energy than the reactants do?
Multiple select question.
exergonic reaction
spontaneous reaction
exothermic
passive
exergonic
endergonic
chemical
catabolic
anabolic
spontaneous
Exergonic reaction, spontaneous reaction, exergonic, spontaneous
When a water molecule is used to remove a phosphate group from ATP, this is called the __________ of ATP.
hydrolysis
What is enthalpy?
The total energy of a system
When does chemical equilibrium occur?
Multiple choice question.
When there is no enzyme available to catalyze a reaction
When the rate of formation of products equals the rate of formation of reactants
When no more reactants are available for the reaction
When a chemical reaction has gone to completion and the rate is zero
B
Multiple Choice Question
What type of reaction or process occurs without needing an input of energy?
Multiple choice question.
Spontaneous
Non-spontaneous
Activated
Instantaneous
A
True or false: When two reactions are coupled, the first reaction must always be exergonic for both to proceed exergonically.
False
A coupled reaction will proceed exergonically when the overall change in free energy of both reactions combined is negative.
According to the equation ΔG = ΔH - T ΔS, which factor determines whether a reaction is spontaneous?
Multiple choice question.
ΔH
ΔS
ΔG
ΔG
The agent that speeds up the rate of a chemical reaction without being changed permanently is called
Multiple choice question.
free energy change
the equilibrium constant
a catalyst
feedback
a catalyst
Which of the following describes the hydrolysis of ATP?
A water molecule is added to ATP resulting in its breakdown to ADP and inorganic phosphate.
A water molecule is removed from ATP resulting in the release of ADP and inorganic phosphate.
A molecule of ATP is formed when a water molecule adds a phosphate group to ADP.
A water molecule is added to ATP resulting in its breakdown to ADP and inorganic phosphate.
In general, enzymes are composed of ___________
proteins
What is the function of enzymes in chemical reactions?
Multiple choice question.
Enzymes control the direction of the reaction.
Enzymes are needed for all chemical reactions to take place.
Enzymes act as catalysts to speed up chemical reactions.
C
When will an endergonic and exergonic reaction that are coupled proceed spontaneously?
Multiple choice question.
When the net free energy change for both reactions combined is negative (exergonic)
When the first reaction is endergonic and the second is exergonic
When the first reaction is exergonic and the second is endergonic
A
Which of these statements describe the free energy (G) change of a spontaneous reaction?
Multiple select question.
There is a positive free energy change.
Free energy is released during product formation.
There is no change in free energy.
The free energy of the products is greater than the reactants.
There is a negative free energy change.
The free energy of the products is less than the reactants.
Free energy is released during product formation.
There is a negative free energy change.
The free energy of the products is less than the reactants.
Select all that apply
What factors determine the direction and rate of a chemical reaction?
Multiple select question.
Catalysts influence the rate of a chemical reaction.
The change in free energy will determine the direction of the reaction.
Thermodynamics governs the direction of a reaction but not the rate of a reaction.
Catalysts determine the direction and rate of a chemical reaction.
Catalysts influence the rate of a chemical reaction.
The change in free energy will determine the direction of the reaction.
Thermodynamics governs the direction of a reaction but not the rate of a reaction.
The energy required to destabilize existing chemical bonds and initiate a chemical reaction is ________ energy
Activation
What is a substrate?
Multiple choice question.
A reactant molecule that binds to the active site of an enzyme
The location on the enzyme where chemical reactions take place
The products of a chemical reaction
The catalyst of a chemical reaction
A reactant molecule that binds to the active site of an enzyme
What is Vmax?
Multiple choice question.
The maximal level of enzyme efficiency
The maximal rate of a chemical reaction
The maximum volume needed for a reaction
The maximum activation energy of a reaction
The maximal rate of a chemical reaction
Why do changes in the pH of the fluid in which an enzyme is dissolved affect the enzyme’s ability to function?
Multiple choice question.
Enzymes have particular pH values at which they function best.
The enzyme’s bonds become too weak to hold the enzyme together due to increased random movement of atoms in the enzyme.
The enzyme becomes inflexible, and induced fit is not possible.
Enzymes have particular pH values at which they function best.
What is the main factor that can affect the rate of a reaction?
Multiple choice question.
Increased activation energy
Thermodynamics
Increased entropy
Catalysis
Catalysis
The initial input of energy needed to overcome repulsion between molecules in a chemical reaction is called ________ energy.
Activation
_________, or reactants, are molecules that bind to an enzyme at the active site and are converted to products in chemical reactions.
substrates
Name environmental factors that affect proper enzyme function.
Multiple choice question.
Temperature and ionic conditions
Temperature and pH
pH and ionic conditions
Temperature, pH, and ionic conditions
Temperature, pH, and ionic conditions
Vmax is the __________ velocity or rate of a chemical reaction.
maximal
Why do most enzymes function maximally in a narrow range of temperature and pH?
Multiple choice question.
Enzymes only function at a narrow range of conditions in which their substrates are available.
Enzymes evolved to function best at body temperature, with an optimum temperature of 37 degrees C.
Exposing enzymes to temperatures and pH outside the optimal range can change the conformation of the active site or denature the protein.
Exposing enzymes to temperatures and pH outside the optimal range can change the conformation of the active site or denature the protein.
Altering the pH outside the optimal range for a protein can cause denaturation and can ______ the function of an enzyme.
not affect
enhance
impair
Impair
Pepsin is an enzyme found in the stomach that functions best at an acidic pH. Why?
Multiple choice question.
All enzymes function best in acidic environments and poorly at basic pH.
All enzymes function best in acidic environments and poorly at neutral pH.
Enzymes are sensitive to pH and function best across a narrow range of pH.
Enzymes are sensitive to pH and function best across a narrow range of pH.
True or false: Each step of a metabolic pathway is catalyzed by a specific enzyme.
True false question.
True
False
True
In order for molecules to achieve the transition state,
___________ energy is necessary.
Activation
What are the two general functions of catabolic pathways?
Multiple select question.
To synthesize new macromolecules that may be needed in cells
To obtain energy for use in endergonic processes
To recycle the components of organic molecules for use in the synthesis of new molecules
To convert matter into energy
To obtain energy for use in endergonic processes
To recycle the components of organic molecules for use in the synthesis of new molecules
During the breakdown of small organic molecules, oxidation occurs when ______.
Multiple choice question.
electrons are added to an atom or molecule
electrons are removed from an atom or molecule
protons are removed from an atom or molecule
protons are added to an atom or molecule
B
Which of these is a synonym for anabolic reactions?
Multiple choice question.
Biosynthetic reactions
Redox synthesis
Allosteric reactions
Catabolic reactions
A
The three levels at which metabolic pathways are regulated are (1)
__________ regulation, (2)
__________regulation, and (3)
__________regulation.
Genetic, cellular, and biochemical
During each step of the metabolic pathway that adds phosphate groups to various sugars, a separate __________ is needed to catalyze the reaction.
Enzyme
A macromolecule that is not recycled but is instead stably maintained is __________.
DNA
The two main functions of ______ pathways are to recycle components of macromolecules and to produce energy intermediates, such as ATP, which are directly used to drive ______ reactions in cells.
catabolic; endergonic
True or false: When an electron is added to a molecule, the molecule is oxidized.
True false question.
True
False
False
Enzymes that cleave the bonds between adjacent amino acids in a protein are called __________.
Proteases
Anabolic reactions are also called __________ reactions.
Biosynthetic
What occurs during the process of autophagy in cells?
Intracellular materials are digested by the lysosomes.
What are the two general functions of catabolic pathways?
To recycle the components of organic molecules for use in the synthesis of new molecules
To obtain energy for use in endergonic processes
What is the function of a protease?
Transport of proteins across the plasma membrane
Protein synthesis
Protein degradation
Protein degradation
Which of these is a synonym for anabolic reactions?
Multiple choice question.
Redox synthesis
Allosteric reactions
Biosynthetic reactions
Catabolic reactions
Biosynthetic reactions
The digestion of intracellular material, such as worn-out organelles, occurs by a process called
___________.
Autophagy
What occurs during the process of autophagy in cells?
Multiple choice question.
Intracellular materials are digested by proteasomes.
Intracellular materials are digested by the lysosomes.
Intracellular materials are digested by the lysosomes.
Ubiquitin ________.
Question 6 options:
is attached to improperly folded proteins and targets them for degradation.
targets proteins for post-translational processing.
is attached to improperly folded proteins.
targets proteins for degradation and post-translational processing.
targets proteins for degradation.
Not E.
