Biology chapter 6 assignment

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

Select the true statement about enzymes.

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

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.

allosteric

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

allosteric

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

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

cofactors

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

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

True or false: Biochemical pathways evolved quickly over time.

false

On the following figure representing how temperature affects the activity of two different enzymes, which of the two curves (left or right) could represent an enzyme isolated from a microorganism that inhabits a hot spring?

on the right curve

In the earliest cells, the first catalyzed chemical reactions were probably reactions composed of how many steps?

one

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.

When you consider the second law of thermodynamics, which of the following is more likely to occur?

-A column of bricks tumbles over -soda fizzes -ice melts

Which of the following statements about chemical reactions are true?

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

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.

Select the characteristics of enzymes.

-Enzymes are not changed or consumed in reactions. -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.

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.

Select the statements that accurately describe cellular enzymes.

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

Select reasons why metabolic pathways are regulated.

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

Select the steps in the ATP cycle.

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

Which of the following statements are correct about noncompetitive inhibitors?

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

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 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.

The optimum pH of most enzymes is

6 to 8

What is the optimal pH range for most human enzymes?

6 to 8

The optimum pH of most enzymes is 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

Which of the following are included in metabolism?

Both the synthesis and breakdown of organic molecules

_______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

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

Competitive

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

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

Entropy increases.

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.

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

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

When a physical system becomes more disordered, the entropy _____.

Increases

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.

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.

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

Sun

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.

The energy that flows through biological systems on Earth ultimately comes from which source?

The Sun

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.

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.

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: Thermodynamics is the study of energy changes in the Universe.

True

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

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

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

energy

All activities of living organisms involve changes in__________, which is 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

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

free energy

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 an ________.

inhibitor

A substance that binds to an enzyme and decreases its activity is called a(n)

inhibitor

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

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

substrates