Biochemistry: Enzymes and Reactions

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Questions and Answers

What effect does competitive inhibition have on enzyme kinetics?

It decreases Vmax and increases Km.

It can be overcome by increasing substrate concentration. (correct)

It increases Vmax and decreases Km.

It decreases the maximum substrate binding affinity.

Which statement correctly describes noncompetitive inhibition?

It results in a higher Km without affecting Vmax.

It lowers Vmax while Km remains unchanged. (correct)

It prevents substrate binding at the active site.

It can be reversed by high concentrations of substrate.

What does a small Km value indicate about an enzyme?

The enzyme requires a higher substrate concentration to reach Vmax.

The enzyme's Vmax is significantly decreased.

The enzyme operates efficiently at lower substrate concentrations. (correct)

The enzyme has a lower binding affinity.

Which process is responsible for breaking down ATP to release energy?

Hydrolysis, which is an exergonic reaction. Signup and view all the answers

What is Vmax in the context of enzyme kinetics?

The maximum velocity of the reaction at peak substrate saturation. Signup and view all the answers

What type of reaction involves the assembly of small molecules into larger ones?

Anabolic Signup and view all the answers

Which term describes a reaction in which free energy is released?

Exergonic Signup and view all the answers

What is the correct relationship between potential energy and kinetic energy?

Potential energy can be converted to kinetic energy. Signup and view all the answers

In which scenario would a reaction be classified as nonspontaneous?

When it absorbs free energy. Signup and view all the answers

What is an example of a catabolic reaction?

Breakdown of glycogen into glucose. Signup and view all the answers

Which of the following statements about ATP hydrolysis is correct?

It facilitates catabolic reactions. Signup and view all the answers

What defines an endergonic reaction?

It requires an input of energy to proceed. Signup and view all the answers

What is the primary role of enzymes in biochemical reactions?

To lower the activation energy of the reaction Signup and view all the answers

Which of the following statements about the active site of an enzyme is accurate?

It is the area where the substrate binds. Signup and view all the answers

What describes the induced fit model of enzyme action?

The enzyme and substrate change shape slightly to enhance the reaction. Signup and view all the answers

What is an allosteric site on an enzyme?

A location that can alter enzyme activity through binding of effectors. Signup and view all the answers

Which characteristic of enzymes allows them to catalyze both forward and reverse reactions?

They are unchanged by the reaction they catalyze. Signup and view all the answers

How do temperature and pH affect enzyme function?

They can alter the rate of enzyme-catalyzed reactions. Signup and view all the answers

Which of the following is true about ribozymes?

They are enzymes made of RNA. Signup and view all the answers

What is a common misconception regarding enzyme specificity?

Enzymes can act on multiple substrates with high efficiency. Signup and view all the answers

Which of the following statements is incorrect regarding how substrates and enzymes interact?

Substrates must change shape to fit the active site. Signup and view all the answers

Which factor does NOT influence enzyme activity?

Color of the substrate Signup and view all the answers

Study Notes

Chemical Reactions and Energy

Chemical reactions are determined by the concentration of reactants and products.
Reactions can be anabolic (building larger molecules from smaller ones) or catabolic (breaking down larger molecules into smaller ones).

Enzyme Structure and Mechanism

Most enzymes are proteins but some are RNA (ribozymes).
Active site: The region of the enzyme where the substrate binds.
Allosteric site: A secondary location where an effector (activator or inhibitor) binds.
Mechanism of enzyme reactions
- Substrates enter the active site.
- The enzyme and substrate change slightly for better catalysis (induced fit model).
- The enzyme lowers activation energy.
- Products are released and the cycle repeats.

Enzyme Function

Enzymes are catalysts, lowering the activation energy needed for a reaction.
This increases the rate of the reaction.
Characteristics of enzyme function:
- Substrate specificity
- Enzymes aren't changed by the reaction.
- They catalyze both forward and reverse reactions
- Function varies with pH and temperature
- Have active sites that bind substrates via induced fit.

Enzyme Regulation

Competitive Inhibition:
- A substance that mimics the substrate inhibits the enzyme by binding to the active site.
- Increasing substrate concentration overcomes this inhibition.
- Km increases (higher concentration of substrate needed to reach half the maximum velocity).
- Vmax stays the same (maximum reaction rate stays the same).
Non-competitive Inhibition:
- A substance binds to a secondary location (allosteric site).
- Substrate still binds, but the inhibitor prevents reaction.
- Km stays the same.
- Vmax decreases (maximum reaction rate decreases).

Biothermodynamics

Exergonic reactions: Release free energy (-ΔG); spontaneous.
Endergonic reactions: Absorb free energy (+ΔG); require energy; nonspontaneous.
Coupled energy reactions: Combining exergonic reactions that provide energy for endergonic reactions (e.g., ATP hydrolysis driving cellular processes).

Potential vs. Kinetic Energy

Kinetic energy: Energy of motion.
Potential energy: Stored energy (e.g., stored in chemical bonds).

Michaelis-Menten Terminology

Vmax: Maximum reaction velocity (or rate).
Km: Substrate concentration at which the reaction rate is half of Vmax. Represents the enzyme's binding affinity
- Lower Km indicates higher binding affinity (less substrate needed to get to 1/2 Vmax).

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Description

This quiz covers the fundamentals of chemical reactions and enzyme mechanisms, including the role of enzymes as catalysts and their structural features. Explore how enzymes function, their specificity, and the significance of anabolic and catabolic reactions in biological systems.