Biol Ch7

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

When the outermost phosphate bond in ATP is hydrolyzed, ATP becomes

ADP and Pi.

Select the true statements about the ATP cycle in cells.

ATP synthesis is an endergonic reaction. ATP hydrolysis is an exergonic reaction.

Cell activities, such as biosynthesis, movement, and membrane transport, are powered by short-term supplies of

ATP.

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

Active site

What is the function of anabolic reactions?

Anabolic reactions are involved in the synthesis of larger molecules from smaller precursor molecules.

Which of the following is the best description of the fit between an enzyme and its substrate?

As the substrate binds to the enzyme, the shape of the active site changes to accommodate the reaction.

Select the true statements about allosteric activators.

Binding of an allosteric activator increases enzyme activity. The binding of an allosteric activator keeps an enzyme in its active configuration.

Select the reasons why competitive and noncompetitive inhibition of an enzyme are similar.

Both competitive and noncompetitive inhibitors can cause the rate of an enzyme-catalyzed reaction to decrease. Both competitive and noncompetitive inhibitors can impair the functioning of an enzyme.

Select reasons why metabolic pathways are regulated.

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

How is the course of metabolism determined in cells?

By the specificity of particular enzymes to only one or a few reactions

Metabolic reactions are broken down into two main categories. Of those two main categories, what type of reactions are involved in the harvest of energy by breaking down larger molecules into smaller molecules?

Catabolic

What is the function of catabolic reactions?

Catabolic pathways are involved in the breakdown of larger molecules into smaller ones.

Select the ways that catalysis affects chemical reactions.

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

The activation energy is a barrier to the formation of products. How can this be overcome?

Catalysts can be used to lower the activation energy.

What statement best describes the first biochemical processes in early cells?

Energy-rich molecules from the environment were taken into cells and used in simple reactions.

What is produced by the binding of enzyme and substrate?

Enzyme-substrate complex

Why do most enzymes function maximally in a narrow range of temperature?

Enzymes are not flexible enough at low temperatures, while higher temperatures can denature the enzyme.

True or false: All cells have the same set of enzymes.

F

On the following figure of a metabolic pathway, the blue arrow points to which of the following?

Final product

Select the statements that correctly describe differences between anabolic and catabolic reactions.

In catabolic reactions large molecules are broken down, while in anabolic reactions large molecules are made from smaller ones. Catabolic reactions release energy, while anabolic reactions need energy input.

What do cells do when the products synthesized by a biochemical pathway are not needed?

Temporarily shut down the pathway

What speeds the formation of carbonic acid in vertebrate red blood cells?

The enzyme carbonic anhydrase

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.

Most enzymes function best at

an optimum temperature.

In biochemical pathways, the product of one reaction

becomes the substrate for the next reaction

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

catalysis.

Substances that lower the activation energy needed to initiate a reaction are called

catalysts

In biochemical pathways, inhibitors that act on early reactions are often the

end product.

The enzyme carbonic anhydrase can speed up the reaction between carbon dioxide and water by more than a __________ times.

million

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

noncompetitive

Even though exergonic reactions proceed spontaneously, cells often need to find ways to make these reactions do which of the following?

proceed faster

Select things that cells must do to support their living metabolism.

supply energy to drive endergonic reactions increase the rate of reactions

Early cells likely obtained molecules for the first biochemical processes from

the environment

The enzymes of a biochemical pathway called the citric acid cycle occur in

the matrix of mitochondria.

Which of the following describes the active site of an enzyme?

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

What causes the rate of some chemical reactions to be very slow?

Large activation energy

Which of the following best describes enzymes?

Proteins or RNA molecules that act as catalysts.

Select the true statements about the enzymes of prokaryotes that live in hot springs.

The optimum temperature of their enzymes corresponds to the normal temperature encountered by the prokaryotes. They have more stable enzymes.

What contributes to the variation in structures and functions among different types of cells?

The particular set of enzymes active in a cell

How do catalysts affect the forward and reverse chemical reaction?

They accelerate both the forwards and the reverse reactions by the same amount.

Select the true statement about enzymes and how they catalyze reactions in a cell.

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

True or False: Catalysts can make an exergonic reaction proceed much faster.

True

An allosteric _________________ increases enzyme activity by binding to an allosteric site, thereby keeping the enzyme in its active configuration.

activator

In a biochemical pathway, each ______ in a sequence acts on the product of the previous stage

enzyme

In a biochemical pathway, each ______ in a sequence acts on the product of the previous stage.

enzyme

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

feedback

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

increases

In general, if a chemical reaction has a higher activation energy,

it will proceed at a slower rate.

The sequential enzymes in biochemical pathways are often

located in specific organelles of the cell.