Enzymes

Select the events that must occur before bonds in the substrate are broken during an enzyme catalyzed reaction.

-A substrate-enzyme complex must form. -The substrate must bind the enzyme. -Amino acids in the enzyme must interact with the substrate.

Select the true statements about cellular enzymes.

-Each enzyme in a cell catalyzes one or a few specific reactions. -Each cell has thousands of enzymes.

Select the characteristics of enzymes.

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

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 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.

What is a substrate?

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

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

Which of the following are included in metabolism?

Both the synthesis and breakdown of organic molecules

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

Denaturation

When a reactant binds to the active site of an enzyme, a(n) ___________-____________ 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

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

The stomach enzyme pepsin functions well at very ___ pH.

Low

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

Lower temperatures prevent the formation of the substrate-enzyme complex while higher temperatures can denature the enzyme.

What statement describes metabolism?

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

What are enzymes?

Proteins or RNA molecules that act as catalysts.

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.

What happens if a chemical substance binds to an enzyme and alters its shape?

The enzyme's activity can be increased or decreased.

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

The final product

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.

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

True

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

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

enzyme

Each ________ in a biochemical pathway acts on the products of the previous reaction.

enzyme

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.

A more efficient way to catalyze a sequence of related biochemical reactions is to combine several proteins into a ________ complex; in this way, the product of each reaction can be delivered to the next enzyme, without being released to diffuse away.

multienzyme

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

true

Select the statements that accurately describe multienzyme complexes.

-Enzymes in multienzyme complexes catalyze a sequence of reactions. -Within the multienzyme complex, products of one reaction can be delivered to the next reaction. -Multienzyme complexes improve catalytic efficiency.

Select the statements that accurately describe cellular enzymes.

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

Order the steps in enzyme catalysis starting at the top.

-Substrate binds to enzyme -Amino acids from enzyme interact with substrate -Bonds in substrate(s) are broken and/or created; product forms -Products dissociate from 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.

The optimum pH of most enzymes is

6 to 8

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.

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

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 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

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

False

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.

A substance that binds to an enzyme and decreases its activity is an

Inhinitor

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.

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 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

Select the true statement about enzymes.

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

How can some enzymes function well at a very low pH?

They maintain their three dimensional shape even at a very low pH.

How many different kinds of enzymes are known in total?

Thousands

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.

coenzyme

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

When several enzymes that catalyze different steps of a sequence of reactions are associated with one another in a noncovalently bonded assembly, they form a(n) complex.

multienzyme

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.

noncompetitive

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

one

Most human enzymes function best between 35 and 40οC, while the enzymes of bacteria that inhabit hot, sulfur springs have a higher ________ temperature.

optimum

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

Active site

Select the ways in which multienzyme complexes improve catalytic efficiency.

-All of the reactions inside the complex can be controlled as one unit. -The product of one reaction can be delivered to the next enzyme more easily. -Because products do not leave the complex, there are no unwanted side reactions.

What type of reactions are involved in the synthesis of larger molecules from smaller precursor molecules?

Anabolic

What is the function of anabolic reactions?

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

(catabolic or anabolic) ells harvest energy during _______ reactions and expand energy during _________ reactions

Catabolic, Anabolic

Select reasons why metabolic pathways are regulated.

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

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.

-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.

What is the optimal pH range for most human enzymes?

6 to 8

The optimum pH of most enzymes is 6 to ___.

8

What is a noncompetitive inhibitor?

A molecule that binds to an allosteric site and prevents the proper functioning of an enzyme

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

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

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

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 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 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

Inhibitors that bind to the active site of an enzyme preventing the binding of substrates are

Competitive inhibitors

What are competitive inhibitors?

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

True or false: Biochemical pathways evolved quickly over time.

False

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

Noncompetitive

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

substrates