Chapter 6 smartbook
Select the true statements about the ATP cycle in cells.
ATP hydrolysis is an exergonic reaction. ATP synthesis is an endergonic reaction.
all cells use a molecule called ___ to carry and release energy cyclically.
ATP or adenosine triphosphate
_____________ energy is the energy required to destabilize existing chemical bonds and initiate a chemical reaction.
Activation
Where does a substrate bind on an enzyme in order for a chemical reaction to take place?
Active site
Which nitrogenous base is a component of ATP?
Adenine
From the list below, select the three components of ATP.
Adenine Ribose A chain of three phosphates
The activation energy is a barrier to the formation of products. How can this be overcome?
Catalysts can be used to lower the activation energy.
Why do catalysts increase the rate of a chemical reaction?
Catalysts stabilize the transition state in a reaction.
energy is a form of potential energy stored within the covalent bonds of molecules.
Chemical
Which of the following statements about the size and turnover rate of the ATP pool in a typical cell are true?
Most cells have a few seconds' supply of ATP. Most cells have to produce more ATP constantly.
Select the statements that accurately describe multienzyme complexes.
Multienzyme complexes improve catalytic efficiency. Enzymes in multienzyme complexes catalyze a sequence of reactions. Within the multienzyme complex, products of one reaction can be delivered to the next reaction
A(n)____________inhibitor binds to an area outside of the active site of an enzyme and impairs proper functioning of the enzyme.
Noncompetitive
In the earliest cells, the first catalyzed chemical reactions were probably reactions composed of how many steps?
One
Select all of the following that can occur during the reduction of an atom or molecule.
One or more electrons are added to the atom or molecule.The net charge of the atom or molecule decreases due to addition of negatively charged electron(s).
Which of the following is true about the regulation of enzyme activity in cells?
Cells can regulate the activity of enzymes by inhibiting or activating them.
Which of the following equations represents the correct relationship between free energy (G), entropy (S), temperature (T), and enthalpy (H)?
G = H - TS
Energy is usually measured as which of the following?
Heat
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
Which of the following statements about oxidized molecules is true?
They have fewer electrons and less energy than reduced molecules.
Select the true statement about enzymes.
They lower the activation energy of a reaction by binding to the substrates.
The rate of an exergonic reaction can be increased by lowering the_____ energy required to destabilize chemical bonds in the reactants.
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
An allosteric _________________ binds to a site in the enzyme other than the active site and by doing so it keeps the enzyme in its active configuration
activator
One __ is equal to the heat required to raise the temperature of one gram of water by one degree celsius.
calorie
In photosynthesis, energy absorbed from sunlight is used to
combine small inorganic molecules into larger organic molecules
Increasing the temperature outside the optimal range for an enzyme can lead to___________ of the enzyme, altering the enzyme's structure and function.
denaturation
During the breakdown of small organic molecules, oxidation occurs when
electrons are removed from an atom or molecule.
A reaction that requires an input of energy is said to be a(n)__________ reaction.
endergonic, non-spontaneous, or not spontaneous
During each step of the metabolic pathway that adds phosphate groups to various sugars, a separate____________is needed to catalyze the reaction.
enzyme
Each_____________ in a biochemical pathway acts on the products of the previous reaction.
enzyme
When a reactant binds to the active site of an enzyme, a(n)____________ complex forms.
enzyme substrate
_______ are proteins or RNA molecules that act as catalysts to speed up reactions in living organisms.
enzymes
A molecule that binds to a site on the enzyme other than the active site and inhibits the enzyme's activity is called a(n)_______________.
noncompetitive
Most human enzymes function best between 35 and 40οC, while the enzymes of bacteria that inhabit hot, sulfur springs have a higher________ temperature.
optimum
A fraction of the energy from the Sun is captured by plants, algae, and some bacteria through the process of
photosynthesis
Green plants, certain bacteria, and algae can all perform the process of ___________________ during which the energy of light is used to synthesize molecules.
photosynthesis
During photosynthesis, small inorganic molecules are combined into organic molecules using energy from
sunlight
ATP hydrolysis has a ______ ΔG
negative or -
Select the true statements about endergonic reactions.
-Endergonic reactions are not spontaneous. -The products have a higher free energy than the reactants. -Endergonic reactions have a positive change in free energy.
Select the true statements about the effect of temperature on an uncatalzyed chemical reaction.
-Increased temperature increases random molecular movements which increases stress on bonds. -Increased temperature increases the rate of the reaction.
Select the statements that accurately describe cellular enzymes.
-Some cellular enzymes are found inside of cellular organelles .-Different enzymes can come together to form complexes .-Not all cellular enzymes are located in the cytoplasm.
Select all of the following that exhibit potential energy only.
-a stretched rubber band-bow ready to fire an arrow-a boulder sitting at the top of a hill-water at the top a dam
Order the steps in enzyme catalysis starting at the top.
1. Substrate binds to enzyme 2. amino acids from enzyme interact with substrate 3. bonds in substrate are broken and or created products form 4. products dissociate from the enzyme
What is the optimal pH range for most human enzymes?
6 to 8
How much energy is released when the outermost phosphate bond of ATP is hydrolyzed under standard conditions?
7.3 kcal/mol
The optimum pH of most enzymes is 6 to
8
An organic molecule has 10 C-H bonds. The full oxidation of all the C-H bonds in this molecule would yield _____ kcal per mole.
988
Is any energy released during ATP hydrolysis and if so, how much?
A considerable amount of energy is released
What is entropy?
A measure of the amount of disorder in a system
Which of the following statements best describes an allosteric inhibitor?
A molecule that binds to a site other than the active site of an enzyme and inhibits the enzyme's function.
What is a noncompetitive inhibitor?
A molecule that binds to an allosteric site and prevents the proper functioning of an enzyme
What is a substrate?
A reactant molecule that binds to the active site of an enzyme
The two main steps in the ATP cycle are the synthesis of ATP from ____ and Pi and the subsequent hydrolysis of ATP, which relates ____ that drives endergonic reactions.
ADP energy
Cells use ____ hydrolysis to drive endergonic reactions
ATP
What molecule is a common energy source for living organisms?
ATP
Select the ways in which multienzyme complexes improve catalytic efficiency.
All of the reactions inside the complex can be controlled as one unit. Because products do not leave the complex, there are no unwanted side reactions. The product of one reaction can be delivered to the next enzyme more easily.
enzymes are enzymes that can exist in either an active or inactive conformation.
Allosteric
site is a specific region of an enzyme to which non-competitive inhibitors bind in order to regulate enzyme activity.
Allosteric
Select the events that must occur before bonds in the substrate are broken during an enzyme catalyzed reaction.
Amino acids in the enzyme must interact with the substrate.The substrate must bind the enzyme.A substrate-enzyme complex must form.
What type of reactions are involved in the synthesis of larger molecules from smaller precursor molecules?
Anabolic
What is the function of anabolic reactions?
Anabolic reactions are involved in the synthesis of larger molecules from smaller precursor molecules.
As living organisms consume other living organisms,
As living organisms consume other living organisms,
Which of the following is the best description of the fit between an enzyme and its substrate?
As the substrate binds to the enzyme, the shape of the active site changes to accommodate the reaction.
In the following chemical reaction, which molecule(s) is(are) reduced? Ae- + B --> A + Be-
B
What is(are) the effect(s) of a molecule binding to an allosteric site on an enzyme?
Binding of a molecule to an allosteric site can inhibit the proper functioning of an enzyme. Binding of a molecule to an allosteric site can enhance the proper functioning of an enzyme.
Enzyme-mediated chemical reactions take place when the substrate molecules bind to the___________ ___________ of an enzyme.
Blank 1: active or activation Blank 2: site
(catabolic or anabolic?) Cells harvest energy during___________ reactions and expend energy during ______________ reactions.
Blank 1: catabolic Blank 2: anabolic
Because cells are too small to maintain significant internal temperature differences, cells rely on___________ reactions rather than a____________ gradient to do work.
Blank 1: chemical Blank 2: temperature, heat, or thermal
redox reaction is a term used to describe an _____-_____ reaction
Blank 1: oxidation Blank 2: reduction
Which of the following are included in metabolism?
Both the synthesis and breakdown of organic molecules
Metabolic reactions are broken down into two main categories. Of those two main categories, what type of reactions are involved in the harvest of energy by breaking down larger molecules into smaller molecules?
Catabolic
What is the function of catabolic reactions?
Catabolic pathways are involved in the breakdown of larger molecules into smaller ones.
Select the ways that catalysis affects chemical reactions.
Catalysts accelerate both the forward and reverse reactions by the same amount. Catalysts reduce activation energy.
Which of the following statements about chemical reactions are true?
Chemical reactions are reversible. A reaction that is exergonic in the forward direction will be endergonic in the reverse direction.
What organic molecules can accept electrons from the active site of one enzyme and then transfer them to another enzyme where the electrons are released to a substrate in a different reaction?
Coenzymes
_____________ are small organic molecules that temporarily attach to an enzyme and promote a chemical reaction without being changed during the reaction.
Coenzymes
What are the small chemicals, usually inorganic ions, that temporarily attach to the surface of an enzyme and promote a chemical reaction?
Cofactors
are small chemical components, usually inorganic ions, such as Zn2+, Cu2+, and Mn2+, that are often found in the active site participating directly in catalysis.
Cofactors
____________ inhibitors bind to the active site of an enzyme and prevent the substrate from binding. Listen to the complete question
Competitive
What are competitive inhibitors?
Competitive inhibitors bind to the active site of an enzyme and prevent substrates from binding.
Which statement about energy conversion is true?
During any type of energy conversion, some of the energy is lost into the environment as heat.
Select the true statements about cellular enzymes.
Each enzyme in a cell catalyzes one or a few specific reactions. Each cell has thousands of enzymes.
On the following figure of a metabolic pathway, the red arrow points to which of the following? P.123
End product
With very few exceptions, all energy that enters biological systems ultimately comes from the
sun
All living things require which of the following, in order to carry out chemical reactions and thereby survive?
Energy
What is the term for the ability to do work?
Energy
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
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
Pepsin is an enzyme found in the stomach that functions best at an acidic pH. Why does pepsin not function well at a pH of 7?
Enzymes are sensitive to pH and function best across a narrow range of pH.
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.
Select the characteristics of enzymes.
Enzymes may be used more than once in a cell. Enzymes lower the activation energy required for new bonds to form in a chemical reaction Enzymes are not changed or consumed in reactions.
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.
True or false: ATP hydrolysis has a positive ΔG.
False
True or false: ATP synthesis is an exergonic reaction.
False
True or false: All cells have the same set of enzymes.
False
True or false: Biochemical pathways evolved quickly over time.
False
True or false: Energy stored in the chemical bonds of a molecule cannot be harvested and used to make new bonds in a different molecule.
False
True or false: The bonds between phosphates in ATP are very difficult to hydrolyze.
False
True or false: When a lion eats a giraffe, it both creates and adds new potential energy to its body.
False
True or false: When an electron is added to a molecule, the molecule is oxidized.
False
rue or false: All of the enzymes that a cell has are found in the cells' cytoplasm.
False
What is the term used to describe the energy of a system that is available to do work?
Free energy
When you consider the second law of thermodynamics, which of the following is more likely to occur?
Ice melts Soda fizzes A column of bricks tumbles over
Select the statements that correctly describe differences between anabolic and catabolic reactions.
In catabolic reactions large molecules are broken down, while in anabolic reactions large molecules are made from smaller ones.Catabolic reactions release energy, while anabolic reaction need energy input.
Select two ways to increase the rate of reactions.
Increase energy of reactants Lower the activation energy
How does temperature affect the functioning of an enzyme?
Increasing the temperature outside the optimal range for an enzyme can alter the enzyme's structure and impair its function.
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.
What are the two main states of energy?
Kinetic energy and potential energy
Which of the following describes the major difference between kinetic and potential energy?
Kinetic energy is the energy of motion and potential energy is associated with the position of an object.
What causes the rate of some chemical reactions to be very slow?
Large activation energy
Why do most enzymes function maximally in a narrow range of temperature?
Lower temperatures prevent the formation of the substrate-enzyme complex while higher temperatures can denature the enzyme.
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
In broad terms, energy can exist in two states:___________ energy and ______________ energy.
Potential Kinetic
What are enzymes?
Proteins or RNA molecules that act as catalysts.
Which line indicates that a catalyst is lowering the activation energy of the reaction?
Red line
Select reasons why metabolic pathways are regulated.
Regulation allows cells to operate efficiently. By regulating metabolic pathways, cells waste less energy. By regulating metabolic pathways, cells conserve raw materials.
What is the first law of thermodynamics?
The first law states that energy cannot be created or destroyed.
Select the true statements about ribozymes.
Some ribozymes catalyze reactions on themselves.-Ribozymes show high substrate specificity.-Ribozymes can greatly accelerate the rate of the reaction
Select the steps in the ATP cycle.
Synthesis of ATP using energy released from exergonic reactions Hydrolysis of ATP to release energy that can be used to drive endergonic reactions
How can the functioning of an enzyme be affected by the external environment?
Temperature and pH can greatly affect the function of some enzymes by causing denaturation.
The energy that flows through biological systems on Earth ultimately comes from which source?
The Sun
Select the true statements about allosteric sites on enzymes.
The binding of a substance to the allosteric site can switch an enzyme between its active and inactive configurations. This is where a non-competitive inhibitor would bind.
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 following acts as an inhibitor of the first enzyme reaction in a metabolic pathway during feedback inhibition?
The final product
How does feedback regulation regulate enzyme activity?
The final product of a metabolic pathway inactivates the first enzyme in the pathway by binding to its allosteric site.
Select the statements that describe the free energy (G) change of a spontaneous reaction.
The free energy of the products is less than the reactants. There is a negative free energy change.
Which of the following statements about ATP is true?
The high energy phosphate bonds in ATP are unstable and, therefore, not used by cells for long-term energy storage.
Which of the ATP's phosphate bonds is hydrolyzed in most cellular reactions?
The outermost
What contributes to the variation in structures and functions among different types of cells?
The particular set of enzymes active in a cell
Why can cells use ATP or ADP hydrolysis to release energy but not AMP?
The phosphate in AMP is not attached by a high energy bond.
Which characteristic of ATP is responsible for its high energy?
The repulsion of the negative phosphate groups
On the following figure representing how temperature affects the activity of two different enzymes, which of the two curves (left or right) could represent an enzyme isolated from a microorganism that inhabits a hot spring?
The right curve
Which of the following is the branch of chemistry concerned with energy changes?
Thermodynamics
Which of the following statements are correct about noncompetitive inhibitors?
They bind to a site other than the active site of the enzyme They prevent the substrate from binding to the enzyme They cause the enzyme to change shape
Select the true statements about allosteric enzymes.
They can exist in either active or inactive form. They have an allosteric site which differs from the active site.
Certain reactions in cells are endergonic. How do cells make those reactions proceed?
They couple them with ATP hydrolysis.
How can some enzymes function well at a very low pH?
They maintain their three dimensional shape even at a very low pH.
Which of the following is true about spontaneous energy transformations?
They proceed to convert matter from a more ordered to a less ordered form.
How many different kinds of enzymes are known in total?
Thousands
True or false: Chemical potential energy stored in the molecules of living organisms can be converted into other forms, such as kinetic energy, light or electricity.
True
True or false: Each step of a metabolic pathway is catalyzed by a specific enzyme.
True
True or false: Heat energy cannot be used by cells to do work.
True
True or false: Substances can bind to an enzyme and change its shape, affecting its activity.
True
True or false: The energy associated with swinging a bat is a type of kinetic energy.
True
True or false: The oxidized form of a molecule has less energy than its reduced form.
True
True or false: Thermodynamics is the study of energy changes in the Universe.
True
What is an example of an object with high potential energy?
Water stored in a reservoir behind a dam
What occurs during a redox reaction?
When an atom or molecule is oxidized, the electron that is removed is transferred to another atom or molecule, which is thereby reduced.
In a chemical reaction, an electron is transferred from molecule X to molecule Y. Which of the two molecules is oxidized in this reaction?
X
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
Name the type of energy that is a form of potential energy stored in chemical bonds.
chemical
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
During the ATP cycle, energy is consumed as well as released. ATP synthesis is a(n) ______ step, while ATP hydrolysis is a(n) ______ step.
endergonic; exergonic
All activities of living organisms involve changes in__________ which is the ability to do work.
energy
The first law of thermodynamics states that the total amount of__________ in the universe remains constant.
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
In _______ inhibition, the end product of a pathway affects the first enzyme in the series to shut down the pathway. Listen to the complete question
feedback
The energy available to do work in a system is called_________ energy
free
The energy available to do work in a system is called___________ energy.
free
During each energy conversion that happens in a living organism, some of the energy dissipates as____________.
heat
Changes in pH affect an enzyme because the interaction of charged amino acid residues in the enzyme are affected by
hydrogen ion concentrations.
In general, energy transformations can proceed spontaneously when disorder
increases
Temperature affects chemical reactions in the following way: increasing the temperature of an uncatalyzed reaction___________ the rate of that reaction.
increases
When a physical system becomes more disordered, the entropy____________
increases
The binding of a substrate usually produces a slight change in the enzyme's shape resulting in a better enzyme-substrate fit; this is called
induced
The binding of a substrate usually produces a slight change in the enzyme's shape resulting in a better enzyme-substrate fit; this is called___________.
induced
A substance that binds to an enzyme and decreases its activity is an
inhibitor
A substance that binds to an enzyme in a way which results in a decrease of enzyme activity is called a(n)
inhibitor
A substance that binds to an enzyme and decreases its activity is called a(n)
inhibitor.
Heat is a measure of the random motion of molecules, a form of _______ energy.
kinetic
Heat is a measure of the random motion of molecules, a form of___________ energy.
kinetic
Living organisms can convert the potential energy stored in chemical bonds into what other forms of energy?
kinetic energypotential energy in the bonds of new moleculeslight energyelectrical energy (electricity)
__ energy is associated with movement, while ___ energy is stored
kinetic, potential
When the free energy change that occurs as a result of a chemical reaction is___________ than zero, the reaction is spontaneous.
less, lower, or smaller
The stomach enzyme pepsin functions well at very___________ PH.
low
Fats are useful as energy storage molecules because they contain
many C-H bonds.
Heat is a measure of the random____________ of molecules
motion or movement
Heat is a measure of the random________________ of molecules.
motion or movement
A more efficient way to catalyze a sequence of related biochemical reactions is to combine several proteins into a_____________ complex; in this way, the product of each reaction can be delivered to the next enzyme, without being released to diffuse away.
multienzyme
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 or multi-enzyme
Exergonic reactions have a negative change in free energy whereas endergonic reactions have a positive change in free energy.
negative positive
If you stretch a rubber band, you will give it ______ energy; and when the rubber band is released, it has _______ energy when it flies through the air
potential; kinetic
In chemical reactions, ___________refers to the process when one or more electrons are added to a molecule or atom. Listen to the complete question
reduction
Chemical reactions are________________which means that they can proceed in either direction
reversible
RNA molecules that have catalytic properties are called___________
ribozymes
______________or reactants, are molecules that bind to an enzyme at the active site and are converted to products in chemical reactions.
substrates
Phosphate bonds in ATP are high energy bonds, because they are
unstable.
According to the equation ΔG = ΔH - T ΔS, which factor determines whether a reaction is spontaneous?
ΔG
What equation is used to evaluate whether a chemical reaction is spontaneous?
ΔG = ΔH - TΔS
