S-Book Chapter 6

Select the true statements about the effect of temperature on an uncatalzyed chemical reaction.

- Increased temperature increases the rate of the reaction. - Increased temperature increases random molecular movements which increases stress on bonds.

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.

- The balance between positively and negatively charged amino acids in the enzyme is shifted. - Enzymes cannot maintain their three-dimensional shape at extreme pHs, such as a pH of 3.

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.

What molecule is a common energy source for living organisms?

ATP

The optimum pH of most enzymes is 6 to ________.

Blank 1: 8

Each _______ in a biochemical pathway acts on the products of the previous reaction.

Blank 1: enzyme

A reaction is said to be __________ when it releases excess free energy and tends to proceed spontaneously.

Blank 1: exergonic

The energy available to do work in a system is called ______ energy.

Blank 1: free

Temperature affects chemical reactions in the following way: increasing the temperature of an uncatalyzed reaction ______ the rate of that reaction.

Blank 1: increases, raises, speeds up, speeds, accelerates, or hastens

A substance that binds to an enzyme and decreases its activity is an ______.

Blank 1: inhibitor

Heat is a measure of the random ______ of molecules.

Blank 1: motion or movement

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.

Blank 1: multienzyme or multi-enzyme

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.

Blank 1: multienzyme or multi-enzyme

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

Blank 1: negative or - Blank 2: positive or +

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

Blank 1: noncompetitive, allosteric, non competitive, or non-competitive

With very few exceptions, all energy that enters biological systems ultimately comes from the ________.

Blank 1: sun or sunlight

Which of the following are included in metabolism?

Both the synthesis and breakdown of organic molecules

What term refers to small chemicals, usually inorganic ions, that temporarily attach to the surface of an enzyme and promote a chemical reaction?

Cofactors

What are competitive inhibitors?

Competitive inhibitors bind to the active site of an enzyme and prevent substrates from binding.

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

What is the first law of thermodynamics?

Energy cannot be created or destroyed.

Which of the following describe how energy is used in chemical reactions? Multiple choice question.

Energy stored in certain chemical bonds can be used to make new bonds.

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.

The energy that flows through most biological systems on Earth ultimately comes from which source? Multiple choice question.

The Sun

The bacterial enzyme pyruvate dehydrogenase contains multiple copies of each of three enzymes for a total of 60 protein subunits. This is an example of _______.

a multienzyme complex

The hydrolysis of ATP has ______.

a negative ΔG

In order to be initiated, all chemical reactions, even exergonic ones, need ______.

activation energy

Enzyme inhibitors ______.

bind to an enzyme and decrease its activity

The process of influencing chemical bonds to lower the activation energy of a reaction is called Blank______. Multiple choice question.

catalysis

Changes in pH affect an enzyme because the interaction of charged amino acid residues in the enzyme are affected by ______.

hydrogen ion concentrations

Heat is a form of ______ energy, because it reflects the random motion of molecules.

kinetic

In order to function efficiently and to conserve energy and raw materials, a cell ______

maintains biochemical pathways active only when their products are needed

An allosteric enzyme is an enzyme that ______.

can exist in either an active or an. inactive conformation

Select reasons why metabolic pathways are regulated.

- By regulating metabolic pathways, cells waste less energy. - Regulation allows cells to operate efficiently. - By regulating metabolic pathways, cells conserve raw materials.

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.

Which of the following statements regarding exergonic reactions are true?

- Exergonic reactions are spontaneous. - Exergonic reactions release energy during product formation.

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

Where does a substrate bind on an enzyme in order for a chemical reaction to take place?

Active site

The branch of chemistry that studies ________ changes is called thermodynamics.

Blank 1: energy

The optimum pH of most enzymes is

6 to 8

What is a substrate?

A reactant molecule that forms a temporary association with an enzyme before being converted to a product

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

Free energy

How does a noncompetitive 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.

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.

What statement describes metabolism?

Metabolism refers to the sum of all chemical reactions that occur within an organism.

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

What are enzymes?

Proteins or RNA molecules that act as catalysts.

What happens if a chemical substance binds to an enzyme and alters its shape?

The enzyme's activity can be increased or decreased.

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.

What is the second law of thermodynamics?

The transformation of energy from one form to another increases entropy.

Which of the following is the branch of chemistry concerned with energy changes?

Thermodynamics

Certain reactions in cells are endergonic. How do cells make those reactions proceed?

They couple them with ATP hydrolysis.

The first law of thermodynamics states that the total amount of _______ in the universe remains constant.

Blank 1: 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.

Blank 1: 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.

Blank 1: entropy or disorder

_________ are small chemical components, usually inorganic ions, such as Zn2+, Cu2+, and Mn2+, that are often found in the active site of an enzyme, participating directly in catalysis.

Blank 1: Cofactors or Enzyme cofactors

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

Blank 1: Competitive

_________ stored in the chemical bonds of a molecule can be used to make new bonds in a different molecule.

Blank 1: Energy, Potential energy, Chemical energy, or Free energy

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

Blank 1: Enzymes or Enzyme catalysts

_________, or reactants, are molecules that bind to an enzyme and are converted to products in chemical reactions.

Blank 1: Substrates

The _________ __________ for an exergonic reaction is lower in the presence of a catalyst for the reaction.

Blank 1: activation Blank 2: energy

Enzyme-mediated chemical reactions take place when the substrate molecules bind to the _______ ________ of an enzyme.

Blank 1: active Blank 2: site

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

Blank 1: allosteric

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.

Blank 1: biochemical or metabolic Blank 2: pathway

Any agent that speeds up the rate of a chemical reaction without being permanently changed or consumed by it is known as a(n) _______

Blank 1: catalyst

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

Blank 1: denaturation, unfolding, or denaturing

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

Blank 1: endergonic, non-spontaneous, or not spontaneous

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

Blank 1: endergonic, non-spontaneous, or not spontaneous

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.

Blank 1: ADP or adenosine diphosphate Blank 2: energy

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

Blank 1: ATP or adenosine triphosphate

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

Blank 1: Activation

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

Blank 1: Allosteric

________ are small organic molecules that temporarily attach to an enzyme and promote the chemical reaction catalyzed by the enzyme.

Blank 1: Coenzymes

All activities of living organisms involve changes in _______, which is the ability to do work.

Blank 1: energy