AP Bio enzyme inhibition competitive vs noncompetitive study guide

What defines competitive inhibition?

Competitive inhibition occurs when an inhibitor competes with the substrate for the active site of an enzyme.

True or False: Competitive inhibitors permanently bind to the enzyme.

False. Competitive inhibitors bind reversibly to the active site.

What effect does increasing substrate concentration have?

Increasing substrate concentration can overcome competitive inhibition, allowing more substrate to bind.

Example of competitive inhibition in industry?

Methotrexate inhibits dihydrofolate reductase, competing with folate in cancer treatment.

Fill in the blank: Competitive inhibitors resemble _______.

substrates.

How does competitive inhibition affect Vmax?

Vmax remains unchanged since high substrate concentration can overcome inhibition.

Describe the relationship between Km and competitive inhibition.

Competitive inhibition increases Km (the Michaelis constant) without changing Vmax.

What happens to the enzyme's active site during competitive inhibition?

The active site is occupied by the inhibitor, preventing substrate binding temporarily.

Cause → Effect: Competitive inhibitor present.

Effect: Reduced rate of reaction until substrate concentration increases.

What is the main characteristic of a competitive inhibitor?

Its structure is similar to that of the substrate, allowing it to bind to the active site.

How can competitive inhibition be quantified?

Using the Michaelis-Menten equation, $\displaystyle v = \\frac{V_{max}[S]}{K_m + [S]}$.

True or False: Competitive inhibitors decrease the turnover number of the enzyme.

False. The turnover number (kcat) remains the same.

Relationship between competitive inhibition and enzyme specificity?

Competitive inhibition can reduce an enzyme's specificity by allowing inhibitors to compete with substrates.

What effect does competitive inhibition have on reaction rate at low substrate concentration?

The reaction rate is significantly lowered because the inhibitor occupies active sites.

How to overcome competitive inhibition?

Increase substrate concentration to ensure more substrate binds than inhibitor.

Key feature of competitive inhibitors?

They can be structurally similar to the enzyme's substrate.

What is noncompetitive inhibition?

A type of enzyme inhibition where the inhibitor binds to an allosteric site, reducing enzyme activity regardless of substrate concentration.

True or False: Noncompetitive inhibitors affect substrate binding.

False. Noncompetitive inhibitors do not prevent substrate binding but reduce enzyme activity.

Effect of noncompetitive inhibition on Vmax?

Vmax decreases because the overall number of active enzymes is reduced while Km remains unchanged.

Fill in the blank: Noncompetitive inhibitors bind to the ____ site.

allosteric

What happens to Km in noncompetitive inhibition?

Km remains constant. Noncompetitive inhibitors do not affect substrate binding affinity.

Example of a noncompetitive inhibitor?

Heavy metals like lead or mercury can noncompetitively inhibit enzymes.

Cause → Effect: Noncompetitive inhibition leads to decreased activity.

The binding of the inhibitor alters the enzyme's structure and functionality.

Comparison: Competitive vs Noncompetitive inhibition.

Competitive: inhibitor competes with substrate for active site. Noncompetitive: inhibitor binds elsewhere, affecting function.

What is an allosteric site?

A site on an enzyme where molecules can bind and influence enzyme activity without preventing substrate binding.

True or False: Noncompetitive inhibition can be reversed.

True. Noncompetitive inhibition can be reversed but not by increasing substrate concentration.

Noncompetitive inhibition requires ____ to reach the same Vmax.

More substrate molecules, but it doesn't restore the original Vmax.

How do noncompetitive inhibitors affect enzyme kinetics?

They lower the maximum reaction rate (Vmax) without changing the Km.

What occurs when a noncompetitive inhibitor binds to the enzyme?

It alters the enzyme's shape, preventing it from catalyzing the reaction effectively.

Example of a biological noncompetitive inhibitor?

Allosteric regulators like ATP or ADP that change enzyme activity.

Complete the sentence: Noncompetitive inhibitors can bind to ____ or ____.

the enzyme alone or the enzyme-substrate complex.

In a graph of enzyme activity, noncompetitive inhibition shows a ____ line.

lower maximum reaction rate with the same Km.