Biology Chapter 6: Enzymes Flashcards

Questions and Answers

In general, enzymes are what kinds of molecules?

Minerals

Lipids

Nucleic acids

Proteins (correct)

Carbohydrates

Enzymes work by _____

Decreasing the potential energy difference between reactant and product

Adding energy to a reaction

Increasing the potential energy difference between reactant and product

Reducing energy of activation (correct)

Adding a phosphate group to a reactant

An enzyme _____

Can bind to nearly any molecule

Is an organic catalyst (correct)

Is a source of energy for endergonic reactions

Increases the energy of activation of a reaction

Is an inorganic catalyst

What name is given to the reactants in an enzymatically catalyzed reaction?

Substrate Signup and view all the answers

As a result of its involvement in a reaction, an enzyme _____

Is unchanged Signup and view all the answers

In a graph of energy vs reactants and products, what part of the parabola is the energy of activation found?

It is found between the reactant and the top or cusp of the curve. Signup and view all the answers

What must be overcome in order for a reaction to proceed?

The energy of activation must be overcome. Signup and view all the answers

Define an exergonic reaction.

A spontaneous chemical reaction, in which there is a net release of free energy. Signup and view all the answers

If exergonic reactions occur spontaneously, what keeps molecules from breaking apart and cell chemistry from racing out of control?

Some energy must be added to get the reaction going; this is known as the energy of activation. Signup and view all the answers

How does a living cell overcome the energy barrier for its metabolic reactions?

A special kind of protein called an enzyme is the answer. Signup and view all the answers

An enzyme serves as a _____, _ without ______.

Biological catalyst, increasing the rate of a reaction without being changed into a different molecule. Signup and view all the answers

Is an enzyme selective or nonselective?

Selective Signup and view all the answers

Why is an enzyme so specific?

Its three-dimensional shape allows it to act only on specific molecules. Signup and view all the answers

What is the substrate?

The reactant on which an enzyme works. Signup and view all the answers

What is the active site?

The specific portion of an enzyme that attaches to the substrate by means of weak chemical bonds. Signup and view all the answers

In a graph of enzymatic activity, what is the most reasonable explanation for low activity at 0 degrees Celsius?

There is too little activation energy available from the environment. Signup and view all the answers

How many active sites are generally found in an enzyme?

One active site at which catalysis can occur. Signup and view all the answers

What happens to enzymes as the substrate concentration increases?

The reaction rate increases until the active site is saturated with substrate. Signup and view all the answers

What happens to the rate of a reaction involving an enzyme when saturation is reached?

The rate of the reaction will not increase with the concentration of substrates. Signup and view all the answers

In a graph of reaction rate vs substrate concentration, at what point does the reaction rate remain constant?

When saturation point happens, where there is a high substrate concentration. Signup and view all the answers

When saturation is reached, the reaction rate is independent of what?

The reaction rate is independent of substrate concentration. Signup and view all the answers

In a graph of reaction rate vs substrate concentration, in which region is the enzyme saturated with substrate?

In the region where there is a high substrate concentration and the hyperbola begins to be a horizontal line. Signup and view all the answers

What is your best option for increasing the rate of the reaction when the enzyme is saturated?

Increase the enzyme concentration Signup and view all the answers

What are enzyme inhibitors?

Molecules other than substrates that bind to enzymes, slowing down the rate of the enzymatic reaction. Signup and view all the answers

What are the two classifications of enzyme inhibitors?

Irreversible and reversible. Signup and view all the answers

What are the two types of reversible enzyme inhibitors?

Competitive and non-competitive. Signup and view all the answers

What is a competitive inhibitor?

An inhibitor that has a structure similar to the substrate. Signup and view all the answers

What is a noncompetitive inhibitor?

An inhibitor that binds to a site on the enzyme that is not the active site. Signup and view all the answers

What does an irreversible inhibitor do?

Forms a covalent bond with an amino acid side group within the active site, preventing substrate binding. Signup and view all the answers

The competitive inhibitor competes with the substrate for the _____ on an enzyme.

Active site. Signup and view all the answers

What happens to the enzyme's shape when a noncompetitive inhibitor is bonded?

The shape of the enzyme is distorted. Signup and view all the answers

Enzyme inhibitors disrupt normal interactions between an enzyme and its _____

Substrate. Signup and view all the answers

How can you decrease the effect of the competitive inhibitors?

They can be outcompeted by adding extra substrate. Signup and view all the answers

What do noncompetitive inhibitors do?

Inhibit the enzyme by binding elsewhere and changing its shape. Signup and view all the answers

What do irreversible inhibitors do?

Bind directly to the active site, permanently altering the enzyme structure. Signup and view all the answers

What is an example of competitive inhibitors?

Medications like penicillin and aspirin. Signup and view all the answers

You have an enzymatic reaction at the optimum pH and temperature. You add a competitive inhibitor and notice the reaction slows down. What can you do to speed the reaction up again?

Add more substrate; it will outcompete the inhibitor and increase the reaction rate. Signup and view all the answers

The phosphorylation of glucose to generate glucose-6-phosphate is catalyzed by hexokinase. This enzyme is allosterically inhibited by its own product, glucose-6-phosphate. This is an example of _____

Feedback regulation. Signup and view all the answers

Feedback inhibition is also known as _____

End-product inhibition. Signup and view all the answers

Which of the following best describes a metastable state?

The metastable state is a state of the substrate in which the reaction can proceed but typically requires a catalyst. Signup and view all the answers

What is the site on an enzyme that will bind the substrate called?

Active site. Signup and view all the answers

Which of the following is an enzyme?

Carboxypeptidase A Signup and view all the answers

The EC system for naming enzymes is based on which of the following criteria?

The six major classes of enzyme function Signup and view all the answers

What may substrate activation involve?

Donation of protons to the enzyme, a change in enzyme conformation induced by substrate binding, formation of temporary covalent bonds, accepting protons from the enzyme. Signup and view all the answers

The induced-fit model involves what?

A conformational change in the shape of the enzyme. Signup and view all the answers

Which of the following is not a means of enzyme regulation?

Saturation Signup and view all the answers

Covalent modification affects the activity of an enzyme by _____

All of the above Signup and view all the answers

Study Notes

Enzymes as Biological Catalysts

Enzymes are primarily proteins that act as organic catalysts to accelerate biochemical reactions without being consumed.
They work by reducing the energy of activation (EA), allowing reactions to proceed more easily.

Substrates and Active Sites

The reactants in enzymatically catalyzed reactions are called substrates.
The active site is the specific region of the enzyme where substrates bind through weak chemical interactions.

Reaction Dynamics

Enzymes remain unchanged after reactions, meaning they can catalyze subsequent reactions.
Increasing substrate concentration typically enhances reaction rates until saturation occurs, at which point all active sites are occupied.

Energy Considerations

Even spontaneous reactions (exergonic) require an initial energy input (energy of activation) to start.
A low reaction rate at temperatures below optimal levels often indicates insufficient energy for the reaction to proceed.

Specificity of Enzymes

Enzymes exhibit high specificity due to their unique three-dimensional structures, allowing them to interact only with particular substrates.
Competitive inhibitors resemble substrates and bind to the active site, while non-competitive inhibitors attach elsewhere, altering the enzyme's shape.

Inhibition Types

Irreversible inhibitors form covalent bonds with enzymes, permanently inactivating them.
Reversible inhibitors can be competitive or non-competitive, affecting enzyme activity without permanent changes.

Regulation of Enzymatic Activity

Feedback inhibition occurs when a product of a metabolic pathway inhibits an enzyme involved in its own synthesis, maintaining metabolic balance.
Enzyme activity can be modulated by processes such as allosteric regulation and covalent modification (e.g., adding phosphate groups).

Metastable States and Catalysis

The metastable state reflects a condition where substrate reactions can occur but typically require a catalyst to overcome energy barriers.
The induced-fit model illustrates how enzyme conformations change in response to substrate binding, enhancing catalytic efficiency.

Enzyme Classification

Enzymes are categorized into six major classes based on their functions, according to the Enzyme Commission (EC) system.
Examples of enzymes include carboxypeptidase A, a well-characterized proteolytic enzyme.

Practical Implications

Competitive inhibitors can be outcompeted by increasing substrate concentration.
Enzyme regulation is essential for cellular function, and understanding these mechanisms informs drug development and metabolic engineering.

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Description

Test your knowledge on enzymes and their functions with this flashcard quiz based on Chapter 6 of Biology. Discover how enzymes act as catalysts in biochemical reactions and learn about their properties and mechanisms. Perfect for preparing for your upcoming biology exam!