Chapter 6

Chemical energy is a form of ______ energy stored in chemical bonds.

potential

If you stretch a rubber band, you will give it_________energy and when the rubber band is release it has _______ energy when it flies through the air.

potential energy kinetic energy

Almost all enzymes bind their substrates with a high degree of

specificity

When a reactant binds to the active site of an enzyme, this produces the enzyme-

substrate complex

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

substrates

Energy that can be used to promote change or do work is called________ energy

usable

What form of energy can be used to drive cellular processes such as muscle contraction and cellular movements?

useable energy

example of an object with high potential energy

water stored behind a dam

Name the type of energy that is a form of potential energy stored in chemical bonds

chemical

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

coenzymes

________inhibitors increase the KM of a reaction but do not change the Vmax.

competitive

when an electon is added to a moecule, the moecule is oxidized

flase

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

free energy

When a physical system becomes more disordered, the entropy

increases

The rate of a chemical reaction that is catalyzed by an enzyme will speed up as substrate concentration________ , but eventually reaches An.

increases, plateau

Two forms of energy

kinetic and potential

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

less

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

less

Enzymes increase the rate of a chemical reaction by________ the activation energy

lower

The sum total of all chemical reactions that occur within an organism is referred to as

metabolism

ATP hydrolysis can be used to drive chemical reactions because the hydrolysis of ATP has a ΔG that is:

negative

Many human enzymes funtion best at 37 *C which is:

Normal body temperture

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

A reaction is said to be ______ when the addition of free energy from the environment is required for the reaction to proceed.

endergonic

Which inhibitors bind to enzymes covalently?

irreversible

In general, enzymes are composed of

proteins

an _____ CHemical reaction will proceed without the input of energy

spontaneous

Which of the following happens during phosphorylation involving glucose?

A phosphate group is transferred from ATP to glucose.

What is a substrate?

A reactant molecule that binds to the active site of an enzyme

What must happen immediately before a reaction occurs with or without a catalyst?

A transition state must be reached.

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.

Common energy source in living organisms

ATP

all cell use a molecule called_______ to carry and release energy cyclically

ATP

___________,energy is the initial input of energy needed to overcome repulsion between molecules in a chemical reaction.

Activation

How can the functioning of an enzyme be affected by the external environment?

Altering the pH can be harmful to an enzyme when the pH is outside the normal or optimal range for that enzyme. Increasing the temperature can greatly affect the functioning of some enzymes by causing denaturation.

correctly describe endergonic reactions.

An input of energy is required. The products have higher free energy than the reactants.

Seond law of thermodynamics

As disorder increases, entropy increases. The transformation of energy from one form to another increases the entropy of a system.

Cells commonly use the hydrolysis of ______ to drive chemical reactions.

Atp

The forward direction of the equation A+B → C+D shows that __________ are the products

C+D

Why do catalysts increase the rate of a chemical reaction?

Catalysts lower the activation energy.

Select all of the cellular processes that require a net input of energy.

Cellular movements Endergonic reactions ATP synthesis

During_______ reactions one or more substances are changed or converted into other substances.

Chemical

How do competitive inhibitors affect the velocity and Km of an enzyme-catalyzed reaction?

Competitive inhibitors raise the substrate concentration at which the velocity is half the maximal velocity. Competitive inhibitors do not change the maximal velocity.

Which of the following are types of energy important to biological processes?

Electrical gradients Mechanical Heat Chemical Light

following that can take place during a chemical reaction.

Electrons are transferred between atoms. Molecules are broken apart. Rearrangements of atoms within molecules occur. Molecules attach to each other to form larger molecules.

Endergonic reactions

Endergonic reactions have a positive change in free energy. Endergonic reactions require the addition of free energy. The products have a higher free energy than the reactants. Endergonic reactions are not spontaneous

the first law of thermodynamics?

Energy can be transferred or transformed from one form to another. Energy is conserved when transferred from one form to another.

Pepsin is an enzyme found in the stomach that functions best at an acidic pH. Why?

Enzymes are sensitive to pH and function best across a narrow range of pH.

How do enzymes lower the activation energy of a chemical reaction?

Enzymes can bring reactants closer together. When reactants are bound to enzymes, they can be strained, making it easier to achieve the transition state.

Select the reasons why changes in the pH of the fluid in which an enzyme is dissolved affect the enzyme's ability to function.

Enzymes have particular pH values at which they function best.

true of exergonic reactions.

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

kinetic energy and Potential energy

In broad terms, energy can exist in two states

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.

describe metabolism

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

What are some examples of cellular processes that require energy?

Muscle contraction, cellular movements, chemical reactions

Which of the following is an accrate description of a coenzyme?

Organic molecules that temporarily attach to an enzyme and promote a chemical reaction without being changed during the reaction

difference of irrversible and reversible inhibitors differ

Reversible inhibitors bind to enzymes noncovalently Irreversible inhibitors bind to enzymes covalently

Name environmental factors that affect proper enzyme function.

Temperature , Ph and inonic conditions

What factors determine the direction and rate of a chemical reaction?

The change in free energy will determine the direction of the reaction. Catalysts influence the rate of a chemical reaction. Thermodynamics governs the direction of a reaction but not the rate of a reaction.

The hydrolysis of ATP can be used to drive a chemical reaction that cannot occur spontaneously because:

The hydrolysis of ATP is exergonic. The hydrolysis of ATP has a negative ΔG.

elect all of the following that can occur during the reduction of an atom or molecule

The net charge of the atom or molecule decreases due to addition of negatively charged electron(s). One or more electrons are added to the atom or molecule.

What is phosphorylation?

The transfer of phosphate group from one molecule to another

Which of the following describes the relationship between substrate concentration and the rate of a chemical reaction?

The velocity increases as substrate concentration increases until it reaches a plateau.

describe the free energy (G) change of a spontaneous reaction.

There is a negative free energy change. Free energy is released during product formation. The free energy of the products is less than the reactants.

What are the two general functions of catabolic pathways?

To obtain energy for use in endergonic processes To recycle the components of organic molecules for use in the synthesis of new molecules

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

True or false: Enzymes are sensitive to environmental conditions and, as a result, many enzymes function best only across a narrow range of temperature and pH.

True

True or false: Straining reactants and bringing them closer together are two common ways enzymes can lower the activation energy required for a chemical reaction.

True

Select the best description of product formation in enzyme-catalyzed reactions:

Two steps: binding or release of substrate and product formation

Why is some energy unusable by living organisms?

When energy transformations occur, the entropy of the system increases, which cannot be harnessed in a useful way.

why do organisms couple exergonic and endergonic reactions?

When exergonic and endergonic reactions are coupled, the endergonic reaction will proceed if the net free energy change is negative.

When will an endergonic and exergonic reaction that are coupled proceed spontaneously?

When the net free energy change for both reactions combined is negative (exergonic)

What is entropy

a measure of the amount of disorder in a system

In order for molecules to achieve the transition state,________ energy is necessary

activation

Enzyme-mediated chemical reactions take place when the substrate molecules bind to the________ _________ of an enzyme

active site

Cells commonly use the hydrolysis of ______ to drive chemical reactions.

adenosine triphosphate

What is the main factor that can affect the rate of a reaction?

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

The agent that speeds up the rate of a chemical reaction without being changed permanently is called

catalyst

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 temporarily attach to the surface of an enzyme and promote a chemical reaction.

cofactors

the ablity to promote change or do work

energy

For living organisms, the total energy (H) is called_______, While the free energy (G) is the amount available to do work .

enthalpy

The enzyme hexokinase recognizes and binds to glucose but does not bind to other similar sugars such as fructose. This is an example of what property?

enzyme specificity

A reaction is said to be ______ when the addition of free engery from the environment is required for the reactions to proceed.

exergonic

What type of reaction results in products that contain less free energy than the reactants do?

exergonic reaction spontaneous exergonic spontaneous reaction

organisms couple ______ and _______ reactions because many vital cellular processes would not porceed without energy input

exergonic reaction and the endergonic reaction

Some energy is unusable by living organisms. This is because energy transformations result in an increase in:

heat entropy and disorder

When a water molecule is used to remove a phosphate group from ATP, this is called the

hydrolysis

Altering the pH outside the optimal range for a protein can cause denaturation and can ______ the function of an enzyme.

impair

The five types of energy that are important in biology are electrical/ion gradient, heat, _____,______ , and mechanical

light , chemical

Enzymes are typically composed of which type of macromolecule?

protein

direction and_________are the two main factors that determine the fate of a chemical reaction.

rate

Consider the reversible reaction: A + B ↔ C + D. Whether C + D are favored over A + B will depend upon:

the energy input required the concentrations of reactants and products

Many of the chemical reactions that occur in cells are endergonic. These reactions are possible because they are coupled to:

the hydrolysis of ATP

What is enthalpy?

the total energy of a system