Biology Chapter 6

__________ 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

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.

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

Chemical

Heat is a measure of the random _________ of molecules.

Movement

Heat is a measure of the random _________ of molecules.

Movements

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

Chemical

During a chemical reaction, which molecules become oxidized?

Molecules that have an electron removed

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

allosteric

___________ 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(n) _________ reaction.

endergonic

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

What is the optimal pH range for most human enzymes?

6 to 8

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 releases ______that drives endergonic reactions.

ADP, Energy

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

ATP

Cells use ___ hydrolysis to drive endergonic reactions.

ATP

What molecule is a common energy source for living organisms?

ATP

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

Allosteric

Which of the following are included in metabolism?

Both the synthesis and breakdown of organic molecules

The process of influencing chemical bonds to lower the activation energy of a reaction is called

Catalysis

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

Chemical reactions are reversible. A reaction that is exergonic in the forward direction will be endergonic in the reverse direction.

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. Listen to the complete question

Coenzyme

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

What are competitive inhibitors?

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

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

Denaturation

Select the statements that accurately describe cellular enzymes. Multiple select question. Different enzymes can come together to form complexes. Not all cellular enzymes are located in the cytoplasm. Some cellular enzymes are found inside of cellular organelles. All cellular enzymes are located in the cytoplasm. All cellular enzymes are proteins.

Different enzymes can come together to form complexes. Not all cellular enzymes are located in the cytoplasm. Some cellular enzymes are found inside of cellular organelles.

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

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

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

Energy

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

______ 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?

Entropy increases.

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/Disorder

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(n) ______-_________ complex form.

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. Listen to the complete question

Enzymes

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. Multiple select question. Enzymes cannot maintain their three-dimensional shape at extreme pHs, such as a pH of 3. The enzyme loses its side chains at an extreme pH, such as a pH of 3. The enzyme is dissolved into amino acids. 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. The balance between positively and negatively charged amino acids in the enzyme is shifted.

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

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

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

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

False

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

Free

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

Free energy

Select the steps in the ATP cycle. Hydrolysis of AMP to produce ADP and a considerable amount of energy Hydrolysis of ATP to release energy that can be used to drive endergonic reactions Synthesis of ATP using energy released from exergonic reactions Synthesis of NADH from ATP and Pi

Hydrolysis of ATP to release energy that can be used to drive endergonic reactions Synthesis of ATP using energy released from exergonic reactions

Select the true statements about the effect of temperature on an uncatalzyed chemical reaction. Multiple select question. Increased temperature raises the activation energy of the reaction Increased temperature decreases the rate of the reaction. Increased temperature increases random molecular movements which increases stress on bonds. Increased temperature increases the rate of the reaction.

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

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

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.

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

Kinetic

What are the two main states of energy?

Kinetic energy and potential energy

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.

Select reasons why metabolic pathways are regulated. Multiple select question. Regulation allows cells to operate efficiently. By regulating metabolic pathways, cells waste less energy. By regulating metabolic pathways, cells conserve raw materials. By regulating metabolic pathways, cells can produce compounds in excess.

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.

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

Substrates

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

Sun/Sunlight

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.

Select the true statements about allosteric sites on enzymes. Multiple select question. This is where a substrate would bind. This is where a competitive inhibitor would bind. 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.

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.

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

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

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

They couple them with ATP hydrolysis.

Select the true statements about allosteric enzymes. Multiple select question. They have an allosteric site which differs from the active site. They can exist in either active or inactive form. They can only be inhibited. Allosteric enzymes are enzymes that are not affected by allosteric inhibitors.

They have an allosteric site which differs from the active site. They can exist in either active or inactive form.

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

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

Which of the following statements are correct about noncompetitive inhibitors? Multiple select question. They prevent the substrate from binding to the enzyme They bind to a site other than the active site of the enzyme They cause the enzyme to change shape They bind to the active site of the enzyme

They prevent the substrate from binding to the enzyme They bind to a site other than the active site of the enzyme They cause the enzyme to change shape

Which of the following is true about spontaneous energy transformations?

They proceed to convert matter from a more ordered to a less ordered form.

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

True

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.

True

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

True

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

True

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

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

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

hydrogen ion concentrations.

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

inhibitor

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

reversible