Biochem Enzyme 1

Questions and Answers

What effect does a non-competitive inhibitor have on the reaction rate?

It has no effect on the reaction rate or the affinity of the substrate.

It affects both the reaction rate and the substrate affinity.

It decreases the reaction rate without affecting the affinity of the substrate for the enzyme. (correct)

It increases the reaction rate by stabilizing the enzyme-substrate complex.

How do competitive inhibitors impact the Km value?

They lower the Km value, increasing substrate affinity.

They have no effect on the Km value.

They raise the Km value, decreasing substrate affinity. (correct)

They decrease the Vmax value without altering the Km value.

In which scenario can an inhibitor bind to an enzyme?

When the enzyme has undergone conformational change.

Only when the enzyme is free and unbound.

When the enzyme is either free or bound to the substrate. (correct)

Only when the substrate is already bound to the enzyme.

What is the impact of allosteric inhibition on the active site?

It causes a conformational change that inhibits substrate binding at the active site. Signup and view all the answers

What characterizes the binding of a competitive inhibitor compared to a non-competitive inhibitor?

It binds to the active site, competing with the substrate. Signup and view all the answers

What is the primary function of an active site in an enzyme?

To facilitate weak electrostatic interactions with substrates Signup and view all the answers

Which of the following statements is true about vitamins in relation to energy metabolism?

Vitamins are essential as coenzymes but do not provide energy Signup and view all the answers

Which of the following best describes a holoenzyme?

An active form of an enzyme with its cofactors Signup and view all the answers

What characterizes the specificity of an active site?

It is unique to a specific substrate due to its precise shape Signup and view all the answers

Which process is NOT associated with the function of the active site?

Contributing to enzyme denaturation Signup and view all the answers

Which vitamin acts as a coenzyme involved in the metabolism of amino acids and nucleic acids?

Folic acid Signup and view all the answers

In the context of enzymatic reactions, what does 'dehydrogenation' refer to?

The removal of hydrogen from a substrate Signup and view all the answers

Which of the following is a consequence of the active site’s specific binding?

Enhanced catalysis for only certain substrates Signup and view all the answers

What role do cofactors play in enzyme function?

They are essential for the overall activity of holoenzymes Signup and view all the answers

What distinguishes glucose as a substrate for certain enzymes?

It has a unique structure that fits specific active sites Signup and view all the answers

What characterizes an endergonic reaction based on free energy levels?

Reactants have lower free energy than products. Signup and view all the answers

What does a negative value of ∆G indicate about a reaction?

The reaction is spontaneous. Signup and view all the answers

In the equation ∆G = ∆H - T∆S, which component represents the internal energy of the system?

∆H Signup and view all the answers

Why is the downhill movement of a ball considered spontaneous?

The initial energy of the ball is higher than the final position. Signup and view all the answers

What is true when ∆G equals zero?

The system is at equilibrium with no net change. Signup and view all the answers

What typically happens to the free energy of reactants in exergonic reactions?

They have a higher free energy level than products. Signup and view all the answers

Which of the following statements about entropy (∆S) is correct?

Entropy contributes to the spontaneity of reactions. Signup and view all the answers

What factor differentiates an endergonic reaction from an exergonic reaction?

The free energy of products is higher in endergonic reactions. Signup and view all the answers

What happens to the kinetic energy of molecules when the temperature increases?

It increases causing molecules to move faster. Signup and view all the answers

Which of the following illustrates the role of catalysts in chemical reactions?

They speed up chemical reactions by lowering activation energy. Signup and view all the answers

What is the first step in the enzymatic reaction process?

Formation of the enzyme-substrate complex. Signup and view all the answers

How does the presence of a catalyst affect the activation energy of a reaction?

Decreases it, facilitating faster reactions. Signup and view all the answers

During which step of the enzymatic process does bond formation occur?

Catalytic step Signup and view all the answers

What signifies the molar concentration in a chemical reaction?

Square brackets [] Signup and view all the answers

What is the correct sequence of steps in the enzymatic reaction process?

Binding, catalytic step, detachment. Signup and view all the answers

In the context of enzymes, what does the term 'activation energy' refer to?

The energy necessary to initiate a chemical reaction. Signup and view all the answers

What results from the collision of substrate molecules in a chemical reaction?

Formation of the enzyme-substrate complex. Signup and view all the answers

What effect does a catalyst have on the rate of a chemical reaction?

It increases the rate by lowering activation energy. Signup and view all the answers

Which type of reaction is characterized by the release of heat and can also be referred to as exothermic?

Exergonic reactions Signup and view all the answers

What effect does increasing the concentration of reactants have on a chemical reaction?

Increases the formation of products Signup and view all the answers

Which of the following is NOT a factor that affects reaction rates?

pH level Signup and view all the answers

What does the equilibrium constant indicate in a chemical reaction?

The ratio of substrate to product concentrations Signup and view all the answers

Which statement about endergonic reactions is true?

They require energy and can be classified as endothermic. Signup and view all the answers

How does temperature generally impact the rates of chemical reactions?

Increased temperature typically increases reaction rates. Signup and view all the answers

Which mechanism most directly contributes to the increased product formation as reactant concentration rises?

More frequent collisions between molecules Signup and view all the answers

Under what condition would the formation of reactants be favored based on equilibrium concepts?

When there is a lower concentration of products Signup and view all the answers

If the temperature of a reaction is decreased, what is the expected outcome on the reaction rate?

The reaction rate will decrease. Signup and view all the answers

What is the primary role of catalysts in chemical reactions?

They lower the activation energy required. Signup and view all the answers

Study Notes

Free Energy Concepts

Free energy (∆G): Portion of total energy in a system available for work.
Endergonic reactions occur when products have higher free energy than reactants (∆G > 0).
Exergonic reactions occur when reactants have higher free energy than products (∆G < 0).
At equilibrium (∆G = 0), no net change occurs in the system.

Reaction Types

Exergonic Reactions:
- Also termed exothermic; energy is released as heat.
- Spontaneous with a negative ∆G.
- Example: Downhill movement of a ball (higher energy to lower energy).
Endergonic Reactions:
- Also termed endothermic; need input of energy for reactions to proceed.
- Nonspontaneous with a positive ∆G.

Equilibrium and Reaction Rates

Equilibrium constant defines the ratio of concentrations of products to reactants.
The constant indicates if a reaction favors product formation (forwards) or reactant formation (backwards).

Factors Affecting Reaction Rates

Temperature: Higher temperature increases molecular movement and reaction rates.
Reactant Concentration: Increasing substrate concentration leads to more collisions and increased product formation.
Catalysts: Enzymes speed up reactions by lowering activation energy, enhancing the rate of reactants being converted into products.

Enzyme Action and Mechanism

Enzymes bind to substrates at the active site, forming an enzyme-substrate complex.
Key steps include:
- Substrate binding.
- Formation of the product through catalytic actions like bond formation/breaking.
- Product detachment from the enzyme.

Enzyme Specificity and Inhibition

Active sites of enzymes are specific to certain substrates, facilitating specific reactions.
Competitive Inhibitors:
- Bind to the active site, competing with the substrate.
- Decrease enzyme affinity for the substrate without affecting the overall reaction maximum velocity (Vmax).
Allosteric Inhibitors:
- Bind to allosteric sites, causing conformational changes that inhibit substrate binding to the active site.
- Can bind to free enzymes or those with substrate already attached, resulting in inactive complexes.

Vitamins and Coenzymes

Vitamins such as ascorbic acid and folic acid act as coenzymes, aiding in metabolic reactions without providing energy directly.
Holoenzymes refer to the complete form of an enzyme, including its protein portion and any necessary cofactors.

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Description

Test your understanding of free energy concepts in chemical reactions, including endergonic and exergonic processes. This quiz will help you differentiate between the energy levels of reactants and products and their implications in thermodynamics.