Biology Enzymes Overview

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Questions and Answers

What is one of the primary functions of enzymes in biochemical reactions?

Consume reactants in the process

Increase the temperature of the reaction

Change the reaction products

Decrease the activation energy required (correct)

Which class of enzymes is involved in oxidation-reduction reactions?

Lyases

Hydrolases

Transferases

Oxidoreductases (correct)

What characterizes the specificity of enzymes?

They can be easily synthesized by the body.

They can catalyze multiple unrelated reactions.

They have a precise enzyme-substrate interaction. (correct)

They only work in high temperatures.

Why do some enzymes require co-factors for their activity?

Co-factors enhance the enzyme's catalytic ability. Signup and view all the answers

Which of the following statements about enzymes is incorrect?

Enzymes are consumed during the reaction. Signup and view all the answers

What model is commonly used to describe enzyme kinetics?

Michaelis-Menten model Signup and view all the answers

Chymotrypsin is often used to illustrate which concept in enzyme mechanisms?

Transition state catalysis Signup and view all the answers

What is the role of metalloenzymes?

To require metal ions for activity Signup and view all the answers

What is the role of enzymes in relation to activation energy?

Enzymes lower the activation energy of a reaction. Signup and view all the answers

Which type of enzyme catalyzes the cleavage of chemical bonds without hydrolysis or oxidation?

Lyases Signup and view all the answers

What happens to the rate of product formation over time during a reaction?

It levels off when the reaction reaches equilibrium. Signup and view all the answers

What is meant by the term 'transition state' in enzyme catalysis?

The transient molecular structure with the highest free energy. Signup and view all the answers

Which type of interaction significantly contributes to the stabilization of the transition state in enzymatic reactions?

Hydrogen bonds and ionic interactions Signup and view all the answers

What best describes the relationship between an enzyme's structure and its substrate for effective catalysis?

The enzyme's structure must be complementary to the transition state. Signup and view all the answers

Which of the following statements is true regarding the role of enzymes in achieving equilibrium?

Enzymes accelerate the attainment of equilibrium but do not shift its position. Signup and view all the answers

Which of the following best describes hydrolases?

They perform hydrolysis reactions. Signup and view all the answers

What is the significance of the Michaelis constant (Km) in enzyme kinetics?

Km is the substrate concentration at which the reaction rate is half of Vmax. Signup and view all the answers

At which substrate concentration range does the initial velocity (V0) show a near-linear increase?

Low substrate concentration Signup and view all the answers

What occurs to the reaction rate when substrate concentration exceeds a certain threshold?

The reaction rate plateaus close to Vmax. Signup and view all the answers

What is the rate-limiting step in enzyme-catalyzed reactions according to the Michaelis-Menten model?

Breakdown of the enzyme to its product. Signup and view all the answers

What occurs to the binding energy of interactions in the context of enzyme-substrate complex formation?

It compensates for the increase in free energy in the system. Signup and view all the answers

How does the initial velocity (V0) change in response to increases in substrate concentration at high levels of substrate?

It increases by smaller extents. Signup and view all the answers

What assumption is made regarding product concentration at the beginning of a reaction in the Michaelis-Menten framework?

Product concentration is negligible. Signup and view all the answers

Why is the concentration of substrate ([S]) considered constant during the initial velocity measurement?

Only a small percentage of substrate is converted to product. Signup and view all the answers

Study Notes

Enzymes

Enzymes are biological catalysts that speed up chemical reactions in living organisms
Enzymes are highly specific, catalyzing a single chemical reaction or a set of closely related reactions.
Enzymes accelerate reactions by lowering the activation energy
Enzymes are not consumed in the reaction

Enzyme properties

Catalytic power: Enzymes greatly accelerate reaction rates, often by orders of magnitude faster than uncatalyzed reactions
High specificity: Enzymes are highly specific for their substrates, meaning they only catalyze reactions involving particular substrates
Enzymes are not changed by the reaction. They are not consumed in the reactions they catalyze

Enzyme mechanisms & categories

Many enzymes require co-factors for activity
- Organic compounds: coenzymes (derived from vitamins)
- Metal ions: metalloenzymes
Enzymes are classified into six major classes based on the type of reaction they catalyze.
- Oxidoreductases: Oxidation-reduction reactions (e.g., lactate dehydrogenase)
- Transferases: Group transfer reactions (e.g., nucleoside monophosphate kinase)
- Hydrolases: Hydrolysis reactions (e.g., chymotrypsin)
- Lyases: Cleavage of chemical bonds (e.g., fumarase)
- Isomerases: Isomerization reactions (e.g., triose phosphate isomerase)
- Ligases: Formation of C—C, C—O, C—S, or C—N bonds (e.g., aminoacyl-tRNA synthetase)

Michaelis Menten Equation

The Michaelis-Menten equation describes the relationship between the initial rate of an enzyme-catalyzed reaction (Vo) and the substrate concentration ([S]).
Kinetic parameters can be drawn from a Michaelis-Menten curve

Enzyme Kinetics

Km is the Michaelis constant; a measure of the enzyme's affinity for its substrate
Vmax is the maximum velocity of the enzyme reaction
Vo is initial velocity when [S] is changing

Enzyme Inhibition

Reversible inhibition: the inhibitor can bind and unbind the enzyme. This can be a competitive or uncompetitive process
Irreversible inhibition: the inhibitor forms a strong covalent bond with the enzyme, thereby permanently inactivating the enzyme

Chymotrypsin

Chymotrypsin is a serine protease that catalyzes the hydrolysis of peptide bonds, cleaving peptide bonds adjacent to aromatic amino acids. Its mechanism involves two phases: acylation and deacylation.
Key residues in the active site are essential for its catalytic function.

Transition state

The transition state is an intermediate state in a chemical reaction with the highest free energy.
The transition state between reactants and products is highly unstable
Enzymes stabilize the transition state and decrease the activation energy, catalyzing the reaction.

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Description

This quiz covers the fundamental concepts of enzymes, including their roles as biological catalysts, properties, and classification. Additionally, it explores the importance of cofactors in enzyme activity and the specificity of enzyme reactions. Test your knowledge on how enzymes function in living organisms.