Enzymology Summary&Quiz lec 4,5,6

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Questions and Answers

Which type of inhibitor competes with the substrate molecules for the active site?

Non-competitive inhibitor

Competitive inhibitor (correct)

Uncompetitive inhibitor

Reversible inhibitor

What is the effect of increasing substrate concentration on competitive inhibition?

Has no effect on the inhibition

Reduces Vmax but not Km

Decreases the affinity of the enzyme for the substrate

Completely abolishes the inhibition (correct)

Which type of inhibitor does not have any structural resemblance to the substrate?

Reversible inhibitor

Non-competitive inhibitor (correct)

Uncompetitive inhibitor

Competitive inhibitor

In non-competitive inhibition, what happens to the Km value when the substrate concentration is increased?

The Km remains unchanged Signup and view all the answers

Which type of inhibition reduces both Vmax and Km?

Uncompetitive inhibition Signup and view all the answers

What is the main characteristic of non-competitive inhibitors?

They irreversibly bind to the enzyme at the active site Signup and view all the answers

Which inhibitor binds to the enzyme-substrate complex but not to the free enzyme?

Uncompetitive inhibitor Signup and view all the answers

What is the effect of increasing substrate concentration on uncompetitive inhibition?

Has no effect on the inhibition Signup and view all the answers

In which type of inhibition does increasing substrate concentration decrease the percentage of enzyme molecules attached to the inhibitor?

Competitive inhibition Signup and view all the answers

What is the main characteristic of reversible inhibitors?

They do not compete with the substrate for the active site Signup and view all the answers

Which of the following is NOT a factor that can make reaction pathways faster?

Classifying enzymes using the IUBMB system Signup and view all the answers

Alcohol dehydrogenases (ADH) are classified as which type of enzyme?

Oxidoreductase enzyme Signup and view all the answers

What part of an enzyme facilitates the chemical reaction?

Active site Signup and view all the answers

Which group of co-enzymes participates in reactions catalyzed by oxidoreductases by donating or accepting hydrogen atoms or electrons?

NAD+ and NADP+ Signup and view all the answers

What is the primary focus of enzymology?

The study of chemical reactions Signup and view all the answers

What class of enzymes catalyze oxidation-reduction reactions, with the substrate being the hydrogen donor?

Oxidoreductases (class 1) Signup and view all the answers

Which class of enzymes cleave bonds without adding water?

Lyases (class 4) Signup and view all the answers

Which of the following is a true characteristic of enzymes?

They can be precipitated by protein precipitating reagents Signup and view all the answers

What percentage of weight do enzymes contain as nitrogen?

16% Signup and view all the answers

What is the main function of transferase enzymes?

Transfer a group from one substrate to another Signup and view all the answers

What is the role of enzymes in chemical reactions?

They accelerate the rate of chemical reaction Signup and view all the answers

What do metalloenzymes contain that is directly bound to the protein or its non-protein components?

Metal ions Signup and view all the answers

Why is enzyme catalysis considered rapid?

Because 1 molecule of an enzyme can act upon about 1000 molecules of the substrate per minute Signup and view all the answers

Enzymes are specific to their substrates. What determines substrate specificity?

The active site Signup and view all the answers

What type of reaction do hydrolases catalyze?

Bond cleavage by adding water Signup and view all the answers

What is required for chemical reactions to start?

Catalysts Signup and view all the answers

How are proteins hydrolyzed inside the body?

By the action of enzymes at body temperature Signup and view all the answers

What is the state called when molecules have an initial input of energy during a chemical reaction?

Transition state Signup and view all the answers

"Almost all enzymes are" what type of biomolecules?

"Proteins" Signup and view all the answers

In the Lock and Key Hypothesis, how is the fit between the substrate and the enzyme's active site described?

Exact, creating a temporary enzyme-substrate complex Signup and view all the answers

What happens in the Induced Fit Hypothesis when a substrate binds to the enzyme?

The enzyme changes its shape to adapt its active site to the specific substrate Signup and view all the answers

What is denoted by the Km value in enzymology?

Substrate concentration at half-maximal velocity Signup and view all the answers

How does enzyme concentration influence enzymatic reaction velocity?

Increasing enzyme concentration increases reaction velocity Signup and view all the answers

What can extreme pH levels do to enzymes?

Denature the enzyme and distort the active site Signup and view all the answers

How do inhibitors affect enzymic reactions?

Reduce the rate of enzymic reactions by binding to the active site Signup and view all the answers

At what point does the reaction velocity reach a saturation point in relation to substrate concentration?

At high substrate concentrations Signup and view all the answers

What is the impact of temperature on enzyme activity?

There is an optimum temperature for most enzymes, beyond which denaturation occurs Signup and view all the answers

What type of reactions do decarboxylases, aldolases, and dehydratases catalyze?

Breaking and forming bonds without water or gases Signup and view all the answers

Which hypothesis suggests that an enzyme changes its shape when a substrate binds?

Induced Fit Hypothesis Signup and view all the answers

Study Notes

Enzymes are biological catalysts that facilitate biochemical reactions, catalyzing the formation of isomers (Class 5 isomerases), the joining of two molecules with ATP hydrolysis (Class 6 ligases), or breaking and forming bonds without water or gases (decarboxylases, aldolases, dehydratases).
The Lock and Key Hypothesis suggests that the fit between the substrate and the enzyme's active site is exact, creating a temporary enzyme-substrate complex.
In the Induced Fit Hypothesis, the enzyme changes its shape (conformation) when a substrate binds, adapting its active site to the specific substrate and reducing the reaction's activation energy.
Enzyme reactions are influenced by substrate concentration, enzyme concentration, product concentration, pH, temperature, and inhibitors/activators.
In enzymic reactions, the reaction velocity increases proportionally with the substrate concentration, reaching a saturation point.
The enzyme's affinity for the substrate is denoted by the Km value, which is the substrate concentration at half-maximal velocity.
Enzyme concentration influences the reaction velocity, making it a useful parameter for enzyme assays.
In a reversible reaction, product concentration affects reaction velocity and can even cause the reaction to reverse or stop when equilibrium is reached.
Enzymes' activities can be influenced by extreme pH levels, which can denature the enzyme and distort the active site, making it difficult for the substrate to bind.
Enzyme activity can be affected by temperature, which has an optimum for most enzymes, and denaturation is a concern for some, affecting the enzyme's ability to function.
Inhibitors can reduce the rate of enzymic reactions by binding to the active site and can be reversible or irreversible.
Enzymes play crucial roles in many biological pathways, and their functioning can be affected by various factors, including substrate concentration, pH, temperature, and inhibitors/activators.

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Enzymology Summary&amp;Quiz lec 4,5,6