Chapter 6 Quiz Questions

During a chemical reaction, which molecules become oxidized? A. Molecules that have an electron removed B. Molecules that have an electron added

A.

____________ energy is the energy required to destabilize existing chemical bonds and initiate a chemical reaction.

Activation

___________ energy is a form of potential energy stored within the covalent bonds of molecules. Kinetic Activation Free Chemical

Chemical energy

In the earliest cells, the first catalyzed chemical reactions were probably reactions composed of how many steps? One Three Two More than three

One

The ___________ site is a specific region of an enzyme to which non-competitive inhibitors bind in order to regulate enzyme activity.

allosteric

Increasing the temperature outside the optimal range for an enzyme can lead to of ____________ the enzyme, altering the enzyme's structure and function.

denaturation

A reaction that requires an input of energy is said to be a(n) ___________ reaction.

endergonic (non spontaneous)

During each step of the metabolic pathway that adds phosphate groups to various sugars, a separate __________ is needed to catalyze the reaction.

enzyme

____________ are proteins or RNA molecules that act as catalysts to speed up reactions in living organisms.

enzymes

Exergonic reactions have a(n) ____________ change in free energy, and endergonic reactions have a(n) ___________ change in free energy.

negative; positive

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) _____________ inhibitor.

noncompetitive

A(n) ____________ inhibitor binds to an area outside of the active site of an enzyme and impairs proper functioning of the enzyme.

noncompetitive

What is the optimal pH range for most human enzymes? 2 to 4 6 to 8 7 to 9 3 to 5

6 to 8

The optimum pH of most enzymes is 6 to ____

8

Select all that apply Select the true statements about the effect of temperature on an uncatalzyed chemical reaction. A. Increased temperature increases random molecular movements which increases stress on bonds. B. Increased temperature raises the activation energy of the reaction C. Increased temperature increases the rate of the reaction. D. Increased temperature decreases the rate of the reaction.

A and C

Select all that apply Which of the following statements about chemical reactions are true? A. A reaction that is exergonic in the forward direction will be endergonic in the reverse direction. B. A reaction that is exergonic in the forward direction will also be exergonic in the reverse direction. C. Chemical reactions are reversible.

A and C

Select the characteristics of enzymes. A. Enzymes are not changed or consumed in reactions. B. Enzymes lower the activation energy required for new bonds to form in a chemical reaction C. Enzymes may be used more than once in a cell. D. Enzymes increase the activation energy of reactions causing the reaction to proceed more slowly

A, B, C (Enzymes lower the activation energy of a reaction causing the reaction to proceed much more quickly than without an enzyme.)

Select all that apply Living organisms can convert the potential energy stored in chemical bonds into what other forms of energy? A. light energy B. kinetic energy C. potential energy in the bonds of new molecules D. electrical energy (electricity) E. sunlight

A, B, C, D

Select all of the following that exhibit potential energy only. A. A stretched rubber band B. Water at the top of a dam C. Swinging a bat D. A boulder rolling down a hill E. Bow ready to fire an arrow F. A boulder sitting at the top of a hill

A, B, E, F

During the breakdown of small organic molecules, oxidation occurs when A. electrons are removed from an atom or molecule. B. protons are removed from an atom or molecule. C. electrons are added to an atom or molecule D. protons are added to an atom or molecule

A.

In order to be initiated, all chemical reactions, even exergonic ones, need A. activation energy B. ATP C. inducers D. protein catalysts

A.

Inhibitors that bind to the active site of an enzyme preventing the binding of substrates are A. Competitive inhibitors B. Noncompetitive inhibitors

A.

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? A. Enzymes are sensitive to pH and function best across a narrow range of pH. B. All enzymes function best in acidic environments and poorly at neutral pH.

A.

Select one true statement about enzymes. A. They lower the activation energy of a reaction by binding to the substrates. B. They are altered by the chemical reaction and can only be used once. C. They raise the activation energy of a reaction by binding to the substrates. D. They are consumed in the chemical reaction and can only be used once.

A.

What are enzymes? A. Proteins or RNA molecules that act as catalysts. B. Proteins that bind to the active site of a catalyst. C. Molecules that are used by cells to supply energy cyclically. D. Molecules that are used by cells for long-term energy storage.

A.

What is a substrate? A. A reactant molecule that binds to the active site of an enzyme B. The location on the enzyme where chemical reactions take place C. The catalyst of a chemical reaction D. The products of a chemical reaction

A.

Which of the following is an accurate description of a coenzyme? A. Organic molecules that temporarily attach to an enzyme and promote a chemical reaction without being changed during the reaction B. Small inorganic ions that temporarily attach to the outside of an enzyme and promote a chemical reaction C. Small molecules permanently attached to the outside of an enzyme that aid in catalysis

A.

Which of the following is true about spontaneous energy transformations? A. They proceed to convert matter from a more ordered to a less ordered form. B. Sometimes they can proceed to convert matter from a more ordered to a less ordered state, however, sometimes the opposite can happen as well. C. They proceed to convert matter from a less ordered to a more ordered form.

A.

Which of the following is true about the regulation of enzyme activity in cells? A. Cells can regulate the activity of enzymes by inhibiting or activating them. B. Cells do not regulate the activity of enzymes. C. Cells can inhibit the activity of enzymes but not increase it. D. Cells can increase the activity of enzymes but not decrease it.

A.

Which statement about energy conversion is true? A. During any type of energy conversion, some of the energy is lost into the environment as heat. B. When potential energy stored in chemical bonds is shifted to different molecule, no energy is lost. C. During catabolic reactions, some of the energy is lost as heat. During anabolic reactions, all of the energy is used to make new bonds.

A.

All living things require which of the following, in order to carry out chemical reactions and thereby survive? A. Energy B. Oxygen (O2) in the environment C. Sunlight

A. Energy

All cells use a molecule called ________ to carry and release energy cyclically.

ATP

What molecule is a common energy source for living organisms? Inorganic phosphate DNA H2O ATP

ATP

___________ enzymes are enzymes that can exist in either an active or inactive conformation.

Allosteric

Select all that apply 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. A. The enzyme loses its side chains at an extreme pH, such as a pH of 3. B. The balance between positively and negatively charged amino acids in the enzyme is shifted. C. The enzyme is dissolved into amino acids. D. Enzymes cannot maintain their three-dimensional shape at extreme pHs, such as a pH of 3.

B and D

Select all the statements that describe the free energy (G) change of a spontaneous reaction. A. There is no change in free energy. B. The free energy of the products is less than the reactants. C. There is a positive free energy change. D. There is a negative free energy change. E. The free energy of the products is greater than the reactants.

B and D

Select all that apply Select the true statements about allosteric enzymes. A. Allosteric enzymes are enzymes that are not affected by allosteric inhibitors. B. They can exist in either active or inactive form. C. They have an allosteric site which differs from the active site. D. They can only be inhibited.

B, C

Select all that apply Select the true statements about allosteric sites on enzymes. A. This is where a competitive inhibitor would bind. B. The binding of a substance to the allosteric site can switch an enzyme between its active and inactive configurations. C. This is where a non-competitive inhibitor would bind. D. This is where a substrate would bind.

B, C

Select all that apply Select reasons why metabolic pathways are regulated. A. By regulating metabolic pathways, cells can produce compounds in excess. B. By regulating metabolic pathways, cells conserve raw materials. C. By regulating metabolic pathways, cells waste less energy. D. Regulation allows cells to operate efficiently.

B, C, D

Select all true statements about endergonic reactions. A. Endergonic reactions have a negative change in the free energy. B. Endergonic reactions have a positive change in free energy. C. The products have a higher free energy than the reactants. D. Endergonic reactions are not spontaneous.

B, C, D (product has higher free energy than reactions = positive change = not spontaneous)

How does temperature affect the functioning of an enzyme? A. Increasing the temperature is beneficial to the functioning of an enzyme and will always cause an increase in the rate of reaction. B. Increasing the temperature outside the optimal range for an enzyme can alter the enzyme's structure and impair its function.

B.

Select the true statement about enzymes. A. They raise the activation energy of a reaction by binding to the substrates. B. They lower the activation energy of a reaction by binding to the substrates. C. They are consumed in the chemical reaction and can only be used once. D. They are altered by the chemical reaction and can only be used once.

B.

What are competitive inhibitors? A. Competitive inhibitors bind to allosteric site on an enzyme and inhibit the enzyme's functioning. B. Competitive inhibitors bind to the active site of an enzyme and prevent substrates from binding. C. Competitive inhibitors bind to the substrate and prevent it from interacting with the enzyme.

B.

What are the two main states of energy? A. Kinetic energy and chemical energy B. Kinetic energy and potential energy C. Chemical energy and potential energy

B.

What is a noncompetitive inhibitor? A. A molecule that binds to the substrate and prevents it from interacting with the enzyme B. A molecule that binds to an allosteric site and prevents the proper functioning of an enzyme C. A molecule that binds to the active site and prevents the proper functioning of an enzyme

B.

What is an example of an object with high potential energy? A. Water rushing down a water fall B. Water stored in a reservoir behind a dam

B.

How does the change in free energy differ between exergonic and endergonic reactions? A. Endergonic reactions have a negative change in free energy whereas exergonic reactions have a positive change in free energy. B. Exergonic reactions have a negative change in free energy whereas endergonic reactions have a positive change in free energy.

B. Exergonic = negative Endergonic = positive

Changes in pH affect an enzyme because the interaction of charged amino acid residues in the enzyme are affected by A. cofactor ions. B. hydrogen ion concentrations. C. covalent bonding. D. allosteric inhibitors.

B. Hydrogen ion concentrations

The process of influencing chemical bonds to lower the activation energy of a reaction is called A. free energy change B. catalysis C. the equilibrium constant D. feedback

B. catalysis

Select all that apply Select the statements that accurately describe cellular enzymes. A. All cellular enzymes are located in the cytoplasm. B. All cellular enzymes are proteins. C. Different enzymes can come together to form complexes. D. Some cellular enzymes are found inside of cellular organelles. E. Not all cellular enzymes are located in the cytoplasm.

C, D, E

How can the functioning of an enzyme be affected by the external environment? A. Factors such as temperature, pH, and ionic conditions do not usually affect the functioning of enzymes. B. Of all external factors, only temperature can have a considerable effect on enzyme activity. C. Temperature and pH can greatly affect the function of some enzymes by causing denaturation.

C.

What is entropy? A. The transfer of energy from one form to another B. A measure of the heat produced by a chemical reaction C. A measure of the amount of disorder in a system

C.

What is the first law of thermodynamics? A. The first law states that some energy becomes unusable when transferred from one form to another. B. The first law states that transfer of energy increases entropy. C. The first law states that energy cannot be created or destroyed.

C.

What statement describes metabolism? A. Metabolism refers only to reactions that expend energy to build molecules. B. Metabolism refers to the effects of pH, temperature, and allosteric substances on enzymes. C. Metabolism refers to the sum of all chemical reactions that occur within an organism. D. Metabolism refers only to reactions that harvest energy by breaking down molecules.

C.

Which of the following describes the activity of a particular enzyme? A. It always increases when a substance binds the enzyme and alters its shape. B. It remains the same even when other substances bind the enzyme and alter its shape C. It can be affected by substances which bind the enzyme and alter its shape.

C.

Which of the following describes the major difference between kinetic and potential energy? A. Potential energy is the energy of motion and kinetic energy is associated with the position of an object. B. Kinetic energy is stored in chemical bonds and potential energy is associated with the position of an object. C. Kinetic energy is the energy of motion and potential energy is associated with the position of an object.

C.

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? A. Allosteric substrates B. Inhibitors C. Coenzymes D. Co-substrates

C. Coenzymes

How does feedback regulation regulate enzyme activity? A. The final product of a metabolic pathway activates the first enzyme in the pathway by binding to the allosteric site. B. The final product of a metabolic pathway inactivates the first enzyme in the pathway by binding to its active site. C. The final product of a metabolic pathway inactivates the first enzyme in the pathway by binding to its allosteric site. D. The final product of a metabolic pathway activates the first enzyme in the pathway by binding to its active site.

C. inactivates by binding to allosteric site

_____________ are small organic molecules that temporarily attach to an enzyme and promote a chemical reaction without being changed during the reaction.

Coenzymes

____________ 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

What are the small chemicals, usually inorganic ions, that temporarily attach to the surface of an enzyme and promote a chemical reaction? Coenzymes Substrates Cofactors Ribozymes

Cofactors (coenzymes are usually organic molecules)

_______________ inhibitors bind to the active site of an enzyme and prevent the substrate from binding.

Competitive

As living organisms consume other living organisms, A. energy is created when new molecules are formed. B. sunlight can boost the energy levels of the molecules that are consumed. C. all of the energy of the first organism is lost. D. potential energy is transferred from one organism to another.

D.

Certain reactions in cells are endergonic. How do cells make those reactions proceed? A. They couple them with other endergonic reactions. B. They couple them with ATP synthesis. C. They use enzymes to turn them into exergonic reactions. D. They couple them with ATP hydrolysis.

D.

What happens if a chemical substance binds to an enzyme and alters its shape? A. The enzyme's activity will always remain the same but its specificity will change. B. The enzyme's activity can only be increased. C. The enzyme's activity can only be decreased. D. The enzyme's activity can be increased or decreased.

D.

Which of the following are included in metabolism? A. Only the breakdown of organic molecules B. Only the synthesis of organic molecules C. Neither the synthesis nor the breakdown of organic molecules D. Both the synthesis and breakdown of organic molecules

D.

Which of the following is the branch of chemistry concerned with energy changes? A. Cytochemistry B. Inorganic chemistry C. Organic chemistry D. Thermodynamics

D. Thermodynamics

What is the term for the ability to do work? Kinetic energy Energy Potential energy ATP

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? Potential energy increases. Entropy increases. The total amount of energy remains constant. Entropy decreases.

Entropy increases (disorder)

True or false: When a lion eats a giraffe, it both creates and adds new potential energy to its body.

False. According to the first law of thermodynamics, energy cannot be created or destroyed. The lion uses potential energy stored in the giraffe's molecules to make its own molecules.

True or false: When an electron is added to a molecule, the molecule is oxidized.

False. Addition of an electron is called reduction.

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. Cells routinely use the energy stored in some chemical bonds to make new bonds.

True or false: All of the enzymes that a cell has are found in the cells' cytoplasm.

False. Enzymes can be located in the cytoplasm, on membranes, and inside of organelles.

True or false: Biochemical pathways evolved quickly over time.

False. They evolved slowly over time.

What is the term used to describe the energy of a system that is available to do work? Enthalpy Entropy Kinetic energy Free energy

Free energy

True or false: The energy associated with swinging a bat is a type of kinetic energy.

True

True or false: Thermodynamics is the study of energy changes in the Universe.

True

True or false: Substances can bind to an enzyme and change its shape, affecting its activity.

True. Cells use molecules called activators and inhibitors that can bind to enzymes, change, their shape, and affect their activity.

True or false: Each step of a metabolic pathway is catalyzed by a specific enzyme.

True. Enzymes are needed at each step in a metabolic pathway to catalyze the reactions.

True or false: Heat energy cannot be used by cells to do work.

True. Heat can only be used if there is a heat gradient, which cannot be done in cells due to their small size.

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. Living organisms store energy as chemical potential energy. They can convert and use energy for movement, light emission, etc.

In a chemical reaction, an electron is transferred from molecule X to molecule Y. Which of the two molecules is oxidized in this reaction? Both are oxidized X Y

X is oxidized

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. electrical chemical mechanical heat

chemical

Because cells are too small to maintain significant internal temperature differences, cells rely on ____________ reactions rather than a ________ gradient to do work.

chemical; heat

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

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

According to the second law of thermodynamics, increases _________ when energy is transferred from one form to another and some energy is lost as heat in the process..

entropy or disorder

During each energy conversion that happens in a living organism, some of the energy dissipates as _________.

heat

During each energy conversion that happens in a living organism, some of the energy dissipates as ___________.

heat

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

A substance that binds to an enzyme and decreases its activity is called a(n) anti-enzyme. substrate. inhibitor. activator.

inhibitor

A substance that binds to an enzyme in a way which results in a decrease of enzyme activity is called a(n) ____________.

inhibitor

Heat is a measure of the random motion of molecules, a form of _______ energy. chemical potential kinetic

kinetic

____________ energy is associated with movement, while _____________ energy is stored energy.

kinetic; potential

When the free energy change that occurs as a result of a chemical reaction is ________ than zero, the reaction is spontaneous.

less

Heat is a measure of the random _____________ of molecules.

movement

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

Chemical reactions are __________, which means that they can proceed in either direction (reactants to products or products to reactants).

reversible

_____________, or reactants, are molecules that bind to an enzyme at the active site and are converted to products in chemical reactions.

substrates