Chapter 6 smartbook
What type of reactions are involved in the synthesis of larger molecules from smaller precursor molecules inside of living cells?
Anabolic
enzyme inhibitors
Bind to an enzyme and decrease its activity
Which of the following are included in metabolism?
Both the synthesis and breakdown of organic molecules
What organic molecules can accept electrons from the active site of one enzyme and then transfer them to another enzyme where it the electrons are released to a substrate in a different reaction?
Coenzymes
___ are small organic molecules that temporarily attach to an enzyme and promote the chemical reaction catalyzed by the enzyme
Coenzymes
Increasing the temperature outside the optimal range for an enzyme can lead to _______ of the enzyme, altering the enzyme's structure and function.
Denaturation
What is the first law of thermodynamics?
Energy cannot be created or destroyed
_______, Or reactants, are molecules that bind to an enzyme and are converted to products in chemical reactions.
Substrates
Select the true statements about allosteric sites on enzymes.
This is where a non-competitive inhibitor would bind. The binding of a substance to the allosteric site can switch an enzyme between its active and inactive configurations.
All living things require which of the following, in order to carry out chemical reactions and thereby survive?
energy
The branch of chemistry that studies ____ changes is called thermodynamics
energy
The first law of thermodynamics states that the total amount of _____ in the universe remains constant
energy
What is the term for the ability to do work?
energy
Work in the cell or in the physical world can only be done with expenditure of ___; it is defined as the capacity to do work.
energy
_____ stored in the chemical bonds of a molecule can be used to make new bonds in a different molecule.
energy
Which of the following is another way to state the second law of thermodynamics?
entropy increases
What is produced by the binding of enzyme and substrate?
enzyme-substrate complex
when a reactant binds to the active site of an enzyme, a(n) ___________ _____________ complex forms
enzyme-susbtrate
______ are proteins or RNA molecules that act as catalysts to speed up reactions in living organisms.
enzymes
What are the two main states of energy?
kinetic energy and potential energy
The bacterial enzyme pyruvate dehydrogenase contains multiple copies of each of the three enzymes for a total of 60 protein subunits. This is an example of
multienzyme complex
Chemical reactions are _____, which means that they can proceed in either direction (reactants to products or products to reactants).
reversible
How much energy is released when the outermost phosphate bond of ATP is hydrolyzed under standard conditions?
7.3 kcal/mol
The hydrolysis of ATP has
A negative ΔG
What is a substrate?
A reactant molecule that forms a temporary association with an enzyme before being converted to a product
Which of the following statements about chemical reactions are true?
A reaction that is exergonic in the forward direction will be endergonic in the reverse direction. Chemical reactions are reversible.
What is the general role of anabolic reactions in the metabolism of a cell?
Anabolic reactions are involved in the synthesis of larger molecules from smaller precursor molecules
In the following chemical reaction, which molecule(s) is(are) reduced? Ae + B —> A + Be
B
An allosteric enzyme is an enzyme that
Can exist in either an active or an inactive conformation.
________ are small chemical components, usually inorganic ions, such as Zn, Cu, and Mn, that are often found in the active site of an enzyme, participating directly in catalysis.
Cofactors
What are competitive inhibitors?
Competitive inhibitors bind to the active site of an enzyme and prevent substrates from binding.
Which of the following describes how energy is used in chemical reactions?
Energy stored in certain chemical bonds can be used to make new bonds.
According to the equation for Gibbs free energy, the free energy (G) equals the _____ minus the product of the temperature and the ______ of the system
Enthalpy; entropy
Most enzymes in the human body work best at neutral pH. Select the reasons why changing the pH of the fluid in which a human enzyme is dissolved (for example to a pH of 3) will affect the enzyme's ability to function.
Enzymes cannot maintain their three-dimensional shape at extreme pHs, such as a pH of 3. The balance between positively and negatively charged amino acids in the enzyme is shifted.
What is the second law of thermodynamics?
Every energy transfer or transformation increases the entropy of the universe.
How does the change in free energy differ between exergonic and endergonic reactions?
Exergonic reactions have a negative change in free energy whereas endergonic reactions have a positive change in free energy.
In many oxidation-reduction reactions, electrons pass in pairs from the active site of the enzyme to a(n) _______ that serves as an electron acceptor, which can then release the electrons to the substrates of another reaction.
coenzyme
What term refers to small chemicals, usually inorganic ions, that temporarily attach to the surface of an enzyme and promote a chemical reaction?
cofactors
______ inhibitors bind to the active site of an enzyme and prevent the substrate from binding.
competitive
A reaction that requires an input of energy is said to be a(n) _____ reaction
endergonic
All activities of living organisms involve changes in _____, which is the ability to do work.
energy
_______ are proteins or RNA molecules that act as catalysts to speed up reactions in living organisms.
enzymes
A reaction is said to be ____ when it releases excess free energy and tends to proceed spontaneously
exergonic
What type of reaction or process releases free energy?
exergonic
The energy available to do work in a system is called
free energy
What is the term used to describe the energy of a system that is available to do work?
free energy
Changes in pH affect an enzyme because the interaction of charged amino acid residues in the enzyme are affected by
hydrogen ion concentrations
Temperature affects chemical reactions in the following way: increasing the temperature of an uncatalyzed reaction ______ the rate of that reaction.
increases
A substance that binds to an enzyme and decreases its activity is an
inhibitor
Heat is a form of ______ energy, because it reflects the random motion of molecules.
kinetic
In broad terms, energy can exist in two states; ___ energy and ___ energy.
kinetic and potential
living organisms can convert the potential energy stored in chemical bonds into what other forms of energy?
kinetic energy potential energy in the bonds of new molecules light energy electrical energy (electricity)
What causes the rate of some chemical reactions to be very slow?
large activation energy
Heat is a measure of the random ____ of molecules
motion
When several enzymes that catalyze different steps of a sequence of reactions are associated with one another in a noncovalently bonded assembly, they form a(n) _________ complex.
multienzyme
As living organisms consume other living organisms,
potential energy is transferred from one organism to another.
Which of the following equations represents the correct relationship between free energy (G), entropy (S), temperature (T), and enthalpy (H)?
G = H - TS
Select the steps in the ATP cycle.
Hydrolysis of ATP to release energy that can be used to drive endergonic reactions. Synthesis of ATP using energy released from exergonic reactions.
Most enzymes only function in a narrow range of temperatures and have an optimum temperature at which they work best. Why?
Lower temperatures prevent the formation of the substrate-enzyme complex while higher temperatures can denature the enzyme.
In order to function effectively and to conserve energy and raw materials, a cell
Maintains biochemical pathways active only when their products are needed
What statement describes metabolism?
Metabolism refers to the sum of all chemical reactions that occur within an organism.
During a chemical reaction, which molecules become oxidized?
Molecules that have an electron removed
During a chemical reaction which molecules become reduced?
Molecules that have one or more electrons added
exergonic reaction have a(n) _____ change in free energy, and endergonic reactions have a(n) ____ change in free energy.
Negative; positive
Which of the following is an accurate description of a coenzyme?
Organic molecules that temporarily attach to an enzyme and promote a chemical reaction without being changed during the reaction
Hydrolysis of which covalent bonds in ATP releases a considerable amount of energy?
Phosphate-phosphate bond
The rate of an exergonic reaction can be increased by lowering the _________ energy required to destabilize chemical bonds in the reactants.
activation
______ energy is the energy required to destabilize existing chemical bonds and initiate a chemical reaction
activation
In order to be initiated, all chemical reactions, even exergonic ones, need
activation energy
The _______ ______ for an exergonic reaction is lower in the presence of a catalyst for the reaction.
activation energy
Where does a substrate bind on an enzyme in order for a chemical reaction to take place?
active site
enzyme-mediated chemical reactions take place when the substrate molecules bind to the _______ ______ of an enzyme.
active site
A(n) ________ inhibitor binds to an area outside of the active site of an enzyme and impairs proper functioning of the enzyme.
allosteric
The ______ site is a specific region of an enzyme to which non-competitive inhibitors bind in order to regulate enzyme activity.
allosteric
_______ enzymes are enzymes that can exist in either an active or inactive conformation.
allosteric
The energy that flows through biological systems on Earth ultimately comes from which source?
sun
with very few exceptions, all energy that enters biological systems ultimately comes from the
sun
In a chemical reaction, an electron is transferred from molecule X to molecule Y. Which of the two molecules is oxidized in the reaction?
X
The optimum pH of most enzymes is
6 to 8
What are enzymes?
Proteins or RNA molecules that act as catalysts.
Which of the following is the branch of chemistry concerned with energy changes?
thermodynamics
Select the true statements about the effect of temperature on an uncatalyzed chemical reaction.
-Increased temperature increases the rate of the reaction. -Increased temperature increases random molecular movements which increases stress on bonds.
The following diagram shows the change in free energy for a catalyzed and uncatalyzed reaction. Match letters to the part of the graph they indicate
A- activation energy of uncatalyzed reaction B- activation energy of catalyzed reaction C- free energy change of the reaction
The two main steps in the ATP cycle are the synthesis of ATP from _____ and Pi, and the subsequent hydrolysis of ATP, which releases _____ that drives endergonic reactions.
ADP and energy
All cells use a molecule called _____ to carry and release energy cyclically
ATP
Cells use ____ hydrolysis to drive endergonic reactions
ATP
What molecule is a common energy source for living organisms?
ATP
How does a non-competitive enzyme inhibitor work?
It binds to a site other than the active site and prevents the proper functioning of the enzyme.
Which of the following describes the activity of a particular enzyme?
It can be affected by substances which bind the enzyme and alter its shape.
Which statement accurately describes the fate of chemical potential energy in living things?
It can be shifted and stored into different molecules, or it can be converted into other forms, such as kinetic energy, electricity, or light.
When a cheetah eats an antelope,
It transfers some of the potential energy stored in the tissues of the antelope to its own body.
What happens if a chemical substance binds to an enzyme and alters its shape?
The enzyme's activity can be increased or decreased.
Which of the ATP's phosphate bonds is hydrolyzed in most cellular reactions?
The outermost
Select the true statements about endergonic reactions.
The products have higher free energy than the reactants. Endergonic reactions have a positive change in free energy. Endergonic reactions are not spontaneous.
When two reactions are coupled in a cell, what determines if they will both proceed spontaneously?
The sum of ΔG of the two coupled reactions (the overall ΔG) should be negative.
A _______ __________ is a sequence of reactions occurring in an individual cell that are organized so that the product of one reaction becomes the substrate of the next.
biochemical pathway
The process of influencing chemical bonds to lower the activation energy of a reaction is called
catalysis
Any agent that speeds up the rate of a chemical reaction without being permanently changed or consumed by it is known as a(n)
catalyst
