Enzymes Prelab

The optimum pH of most enzymes is 6 to ____.

8

What is a substrate? Multiple choice question. The catalyst of a chemical reaction A reactant molecule that binds to the active site of an enzyme The products of a chemical reaction The location on the enzyme where chemical reactions take place

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

Where does a substrate bind on an enzyme in order for a chemical reaction to take place? Multiple choice question. Catalytic site Carbon molecules Enzyme-substrate complex Active site

Active site

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

Allosteric

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

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? Multiple choice question. The left curve The right curve

The right curve.

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

True

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

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

When a reactant binds to the active site of an enzyme, a(n) ______________-________________ complex forms.

enzyme-substrate

The stomach enzyme pepsin functions well at very __________ pH.

low

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

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

optimum

RNA molecules that have catalytic properties are called ______________ .

ribozymes

What is the optimal pH range for most human enzymes? Multiple choice question. 2 to 4 7 to 9 3 to 5 6 to 8

6 to 8

What is the optimal pH range for most human enzymes? Multiple choice question. 7 to 9 3 to 5 6 to 8 2 to 4

6 to 8

Which of the following statements best describes an allosteric inhibitor? Multiple choice question. A molecule that binds to the active site of an enzyme and inhibits the enzyme's function. A molecule that binds to a site other than the active site of an enzyme and inhibits the enzyme's function. A molecule that binds to the substrate of an enzyme and inhibits the enzyme's function. A molecule that binds to the allosteric site of an enzyme to keep an enzyme active.

A molecule that binds to a site other than the active site of an enzyme and inhibits the enzyme's function.

Which of the following statements best describes an allosteric inhibitor? Multiple choice question. A molecule that binds to the allosteric site of an enzyme to keep an enzyme active. A molecule that binds to the active site of an enzyme and inhibits the enzyme's function. A molecule that binds to the substrate of an enzyme and inhibits the enzyme's function. A molecule that binds to a site other than the active site of an enzyme and inhibits the enzyme's function.

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? Multiple choice question. A molecule that binds to the substrate and prevents it from interacting with the enzyme A molecule that binds to the active site and prevents the proper functioning of an enzyme A molecule that binds to an allosteric site and prevents the proper functioning of an enzyme

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

Select the ways in which multienzyme complexes improve catalytic efficiency. Multiple select question. 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. The concentration of substances inside the multienzyme complex can be raised several-fold compared to cytoplasm. Because products do not leave the complex, there are no unwanted side reactions.

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.

Select the events that must occur before bonds in the substrate are broken during an enzyme catalyzed reaction. Multiple select question. Amino acids in the enzyme must interact with the substrate. A substrate-enzyme complex must form. The substrate-enzyme complex must be broken. The substrate must bind the enzyme. An enzyme-product complex must be formed.

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

Which of the following is the best description of the fit between an enzyme and its substrate? Multiple choice question. The active site of the enzyme is permanently changed once it encounters the substrate. As the product is released, the enzyme is degraded. The enzyme and its substrate fit like a lock and key - very rigid. As the substrate binds to the enzyme, the shape of the active site changes to accommodate the reaction.

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

Select all that apply What is(are) the effect(s) of a molecule binding to an allosteric site on an enzyme? Multiple select question. Binding of a molecule to an allosteric site will have no effect on the functioning of 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.

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.

Which of the following is true about the regulation of enzyme activity in cells? Multiple choice question. Cells do not regulate the activity of enzymes. Cells can increase the activity of enzymes but not decrease it. Cells can inhibit the activity of enzymes but not increase it. Cells can regulate the activity of enzymes by inhibiting or activating them.

Cells can regulate the activity of enzymes by inhibiting or activating them.

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? Multiple choice question. Coenzymes Co-substrates Allosteric substrates Inhibitors

Coenzymes

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? Multiple choice question. Inhibitors Co-substrates Coenzymes Allosteric substrates

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? Multiple choice question. Ribozymes Substrates Coenzymes Cofactors

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

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

Cofactors Reason: Substrates bind to the enzyme and are transformed into products.

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

Competitive

What are competitive inhibitors? Multiple choice question. Competitive inhibitors bind to the substrate and prevent it from interacting with the enzyme. Competitive inhibitors bind to the active site of an enzyme and prevent substrates from binding. Competitive inhibitors bind to allosteric site on an enzyme and inhibit the enzyme's functioning.

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

Select the true statements about cellular enzymes. Multiple select question. Each enzyme in a cell catalyzes one or a few specific reactions. Each enzyme in a cell can catalyze many (tens to hundreds) different reactions. Each cell has thousands of enzymes. Each cell has only a few types of enzymes.

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

What is produced by the binding of enzyme and substrate? Multiple choice question. Activation energy Catalyst Enzyme-substrate complex Transition state

Enzyme-substrate complex

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

Enzymes

Select all that apply Select the characteristics of enzymes. Multiple select question. Enzymes are not changed or consumed in reactions. Enzymes lower the activation energy required for new bonds to form in a chemical reaction.increase 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 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.

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? Multiple choice question. All enzymes function best in acidic environments and poorly at neutral pH. Enzymes are sensitive to pH and function best across a narrow range of pH.

Enzymes are sensitive to pH and function best across a narrow range of pH.

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? Multiple choice question. Enzymes are sensitive to pH and function best across a narrow range of pH. All enzymes function best in acidic environments and poorly at neutral pH.

Enzymes are sensitive to pH and function best across a narrow range of pH.

Select the statements that accurately describe multienzyme complexes. Multiple select question. Enzymes in multienzyme complexes catalyze a sequence of reactions. Enzymes in multienzyme complexes are bound covalently. Within the multienzyme complex, products of one reaction can be delivered to the next reaction. Multienzyme complexes improve catalytic efficiency.

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.

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

False

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

Increased temperature increases the rate of the reaction. Increased temperature increases random molecular movements which increases stress on bonds. Reason: Higher temperature does not raise the activation energy of a reaction (that would make the reaction slower). When higher temperatures affect the activation energy of a reaction (for example, by adding stress to molecular bonds as molecules move faster) it typically lowers the activation energy.

How does temperature affect the functioning of an enzyme? Multiple choice question. Increasing the temperature is beneficial to the functioning of an enzyme and will always cause an increase in the rate of reaction. Increasing the temperature outside the optimal range for an enzyme can alter the enzyme's structure and impair its function.

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? Multiple choice question. It always increases when a substance binds the enzyme and alters its shape. It remains the same even when other substances bind the enzyme and alter its shape It can be affected by substances which bind the enzyme and alter its shape.

It can be affected by substances which bind the enzyme and alter its shape.

Why do most enzymes function maximally in a narrow range of temperature? Multiple choice question. Enzymes evolved to function best at 37οC. Substrates are only available at a narrow range of temperature conditions. Lower temperatures prevent the formation of the substrate-enzyme complex while higher temperatures can denature the enzyme.

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

Select the statements that accurately describe cellular enzymes. Multiple select question. 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. Different enzymes can come together to form complexes. All cellular enzymes are proteins.

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.

Which of the following is an accurate description of a coenzyme? Multiple choice question. Small inorganic ions that temporarily attach to the outside of an enzyme and promote a chemical reaction Organic molecules that temporarily attach to an enzyme and promote a chemical reaction without being changed during the reaction Small molecules permanently attached to the outside of an enzyme that aid in catalysis

Organic molecules that temporarily attach to an enzyme and promote a chemical reaction without being changed during the reaction

What are enzymes? Multiple choice question. Molecules that are used by cells for long-term energy storage. Proteins that bind to the active site of a catalyst. Proteins or RNA molecules that act as catalysts. Molecules that are used by cells to supply energy cyclically.

Proteins or RNA molecules that act as catalysts.

Select the true statements about ribosomes. Multiple select question. Ribosomal RNA functions as a catalyst. Ribosomal proteins are the key catalysts in a ribosome, and ribosomal RNA provides the structural framework that orients the catalytic proteins. Researchers now know that ribosomal RNA is actually a type of catalytic protein. Ribosomes are essentially large ribozymes.

Ribosomal RNA functions as a catalyst. Ribosomes are essentially large ribozymes.

Order the steps in enzyme catalysis starting at the top:

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

Fill in the blanks to complete the sentence. _____________, or reactants, are molecules that bind to an enzyme at the active site and are converted to products in chemical reactions.

Substrates

How can the functioning of an enzyme be affected by the external environment? Multiple choice question. Of all external factors, only temperature can have a considerable effect on enzyme activity. Factors such as temperature, pH, and ionic conditions do not usually affect the functioning of enzymes. Temperature and pH can greatly affect the function of some enzymes by causing denaturation.

Temperature and pH can greatly affect the function of some enzymes by causing denaturation.

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. 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. 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. Multiple select question. The binding of a substance to the allosteric site can switch an enzyme between its active and inactive configurations. This is where a competitive inhibitor would bind. This is where a substrate would bind. 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? Multiple choice question. The enzyme's activity can only be increased. The enzyme's activity can only be decreased. The enzyme's activity can be increased or decreased. The enzyme's activity will always remain the same but its specificity will change.

The enzyme's activity can be increased or decreased. Reason: If an enzyme's shape is altered, there is a very high probability that its activity will also change.

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

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

Select the true statements about allosteric enzymes. Multiple select question. 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.

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. Multiple choice question. 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 are altered by the chemical reaction and can only be used once. They raise the activation energy of a reaction by binding to the substrates.

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

How can some enzymes function well at a very low pH? Multiple choice question. They form multienzyme complexes to hold charged amino acid residues within the interior, away from hydrogen ions. When the substrate binds to the active site, it induces changes in the enzyme which counteract the effect of the pH. They maintain their three dimensional shape even at a very low pH. Most enzymes have evolved in such a way that they can function in the entire range of the pH scale.

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

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

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

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, non-competitive, or noncompetitive

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

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

denaturation, unfolding, or denaturing

Changes in pH affect an enzyme because the interaction of charged amino acid residues in the enzyme are affected by Multiple choice question. cofactor ions. covalent bonding/ allosteric inhibitors. hydrogen ion concentrations.

hydrogen ion concentrations.

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

increases, raises, speeds up, speeds, accelerates, or hastens

The binding of a substrate usually produces a slight change in the enzyme's shape resulting in a better enzyme-substrate fit; this is called ___________ fit.

induced

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

inhibitor

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

inhibitor or allosteric inhibitor

A substance that binds to an enzyme and decreases its activity is called a(n) Multiple choice question. anti-enzyme. inhibitor. substrate. activator.

inhibitor.

The stomach enzyme pepsin functions well at very ___________ pH.

low or acidic

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.

multi-enzyme

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

noncompetitive

RNA molecules that have catalytic properties are called __________________.

ribozymes

Which of the following is an accurate description of a coenzyme? Multiple choice question. Organic molecules that temporarily attach to an enzyme and promote a chemical reaction without being changed during the reaction Small molecules permanently attached to the outside of an enzyme that aid in catalysis Small inorganic ions that temporarily attach to the outside of an enzyme and promote a chemical reaction

Organic molecules that temporarily attach to an enzyme and promote a chemical reaction without being changed during the reaction Why not small molecules permanently......? Reason: This is the definition of a prosthetic group. Why not Small inorganic ions that temporarily........? Reason: This is the definition of a cofactor

What contributes to the variation in structures and functions among different types of cells? Multiple choice question. The chromosomes present in a particular cell The amount of free energy The particular set of enzymes active in a cell The amount of ATP produced

The particular set of enzymes active in a cell

How many different kinds of enzymes are known in total? Multiple choice question. Hundreds Thousands Only a few Millions

Thousands