Chapter 6 Cell Energy Connect

Why do catalysts increase the rate of a chemical reaction?

Catalysts stabilize the transition state in a reaction.

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.

What statement describes metabolism?

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

Which of the following statements about oxidized molecules is true?

They have fewer electrons and less energy than reduced molecules.

___ 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

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

Enzyme-mediated chemical reactions take place when the substrate molecules bind to the _____ ______of an enzyme.

active site

Which nitrogenous base is a component of ATP? Thymine Cytosine Adenine Guanine

adenine

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

A substance that binds to an enzyme in a way which results in a decrease of enzyme activity is called a _____ .

allosteric inhibitor

A molecule that binds to a site on the enzyme other than the active site and inhibits the enzyme's activity is called a ___ inhibitor.

allosteric or noncompetitive

In photosynthesis, energy absorbed from sunlight is used to

combine small inorganic molecules into larger organic molecules

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

competitive

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 ___ reaction.

endergonic

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

enzyme

When a reactant binds to the active site of an enzyme, a ___ ___ -complex forms.

enzyme- substrate

What is produced by the binding of enzyme and substrate?

enzyme-substrate complex

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

enzymes

True or false: ATP synthesis is an exergonic reaction.

false

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

false

A _____ inhibitor binds to an area outside of the active site of an enzyme and impairs proper functioning of the enzyme.

noncompetitive or allosteric

Hydrolysis of which covalent bonds in ATP releases a considerable amount of energy?

phosphate- phosphate bonds

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

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 and kinetic

In broad terms, energy can exist in two states: ___energy and ____energy.

potential and kinetic

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

sun

Which of the following acts as an inhibitor of the first enzyme reaction in a metabolic pathway during feedback inhibition?

the final product

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 enhance the proper functioning of an enzyme. -Binding of a molecule to an allosteric site can inhibit the proper functioning of an enzyme.

Select the ways that catalysis affects chemical reactions.

-Catalysts accelerate both the forward and reverse reactions by the same amount. -Catalysts reduce activation energy.

Select the true statements about endergonic reactions.

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

Select the characteristics of enzymes.

-Enzymes lower the activation energy required for new bonds to form in a chemical reaction -Enzymes may be used more than once in a cell. -Enzymes are not changed or consumed in reactions.

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

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

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.

-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.

Select 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.

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.

Select all of the following that exhibit potential energy only.

-Water at the top of a dam -Bow ready to fire an arrow -A stretched rubber band -A boulder sitting at the top of a hill

From the list below, select the three components of ATP.

-adenine -ribose -a chain of three phosphates

Living organisms can convert the potential energy stored in chemical bonds into what other forms of energy?

-potential energy in the bonds of new molecules -light energy -electrical energy (electricity) -kinetic energy

Is any energy released during ATP hydrolysis and if so, how much?

A considerable amount of energy is released

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

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

ATP

Cells use ___ hydrolysis to drive endergonic reactions.

ATP

Which of the following are included in metabolism?

Both the synthesis and breakdown of organic molecules

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.

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 active site of an enzyme?

It is the part of the enzyme where the substrate fits.

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 are enzymes?

Proteins or RNA molecules that act as catalysts.

Which characteristic of ATP is responsible for its high energy?

The repulsion of the negative phosphate groups

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

They couple them with ATP hydrolysis.

What is an example of an object with high potential energy?

Water stored in a reservoir behind a dam

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

catalyst

______ energy is a form of potential energy stored within the covalent bonds of molecules.

chemical

During the ATP cycle, energy is consumed as well as released. ATP synthesis is a ______ step, while ATP hydrolysis is a ______ step.

endergonic; exergonic

All living things require which of the following, in order to carry out chemical reactions and thereby survive?

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

Which of the following is another way to state the second law of thermodynamics?

entropy increases

In ___ inhibition, the end product of a pathway affects the first enzyme in the series to shut down the pathway.

feedback

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 called a ...

inhibitor

What are the two main states of energy?

kinetic and potential

___ energy is associated with movement, while ___ energy is stored energy.

kinetic and potential

In chemical reactions ___ refers to the process when one or more electrons are added to a molecule or atom

reduction

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

substrate

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

substrates

Select the true statement about enzymes.

they lower the activation energy of a reaction by binding to the substrates.

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: 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

Phosphate bonds in ATP are high energy bonds, because they are

unstable because they are negatively charged