Enzymes and Their Properties

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Questions and Answers

What is the primary function of enzymes in a chemical reaction?

Increase the free energy of reactants

Convert substrates into products irreversibly

Change the equilibrium position of the reaction

Lower the energy barrier for the reaction (correct)

Which model of enzyme activity suggests that the active site undergoes a conformational change to fit the substrate?

Lock and key model

Static model

Dynamic model

Induced fit model (correct)

What aspect of the active site promotes high-affinity binding of a substrate?

Exclusion of all cofactors

Size and shape of the active site (correct)

Temperature of the reaction environment

Presence of only non-polar amino acids

How do enzymes lower the activation energy of a reaction?

By inducing strain in substrate bonds Signup and view all the answers

What does the term 'proximity effect' refer to in enzyme catalysis?

The spatial arrangement of substrates in the active site Signup and view all the answers

Which statement about enzymes is NOT true?

They change the free energy of reactants Signup and view all the answers

What type of groups do enzymes provide that are critical for catalysis?

Acidic, basic, or other types of groups Signup and view all the answers

Which of the following is NOT a property of the active site in enzymes?

Contains every possible amino acid Signup and view all the answers

What role do isoenzymes play in response to cell signals?

They may respond differently to specific cell signals due to regulatory properties. Signup and view all the answers

Which of the following is NOT a characteristic of all enzymes?

They only work in aerobic conditions. Signup and view all the answers

What makes the CK2-MB isoenzyme useful as a diagnostic marker?

It is unique to myocardial muscle and indicates specific damage. Signup and view all the answers

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

To bind substrates and facilitate the reaction. Signup and view all the answers

Ribozymes are unique because they are composed primarily of which type of molecule?

RNA. Signup and view all the answers

Which of the following correctly describes the formation of an enzyme-substrate complex?

It forms transiently during the catalytic process. Signup and view all the answers

Which cofactor is typically associated with oxidative reactions?

NAD+. Signup and view all the answers

What happens after the enzyme-substrate complex (ES) forms in the catalytic cycle?

The substrate converts into product while still bound to the enzyme. Signup and view all the answers

What is one of the key components of the serine protease mechanism of catalysis?

Tetrahedral oxyanion intermediate Signup and view all the answers

Which amino acids are primarily involved in the catalytic triad of serine proteases?

Ser, His, and Asp Signup and view all the answers

Which factor does NOT affect enzyme catalytic activity?

Color of the enzyme Signup and view all the answers

What effect does increasing temperature generally have on reaction rates?

Increases reaction rates until denaturation occurs Signup and view all the answers

Which statement best describes the relationship between pH and enzyme activity?

Every enzyme has a specific pH range for optimal activity Signup and view all the answers

What happens to the active site of an enzyme when the temperature is too high?

It can denature and lose functionality Signup and view all the answers

What describes the effect of substrate concentration on the reaction rate of enzymes?

Reaction rate increases with substrate concentration until saturation is reached Signup and view all the answers

Which of the following is a consequence of pH affecting enzymatic activity?

Altered ionization states of amino acids Signup and view all the answers

Why is it essential for serine proteases to maintain a specific structural configuration?

To facilitate efficient substrate binding and catalysis Signup and view all the answers

What is a characteristic of the optimum pH for an enzyme's activity?

It varies among different enzymes Signup and view all the answers

What role do enzymes play in biochemical reactions?

They act as biological catalysts. Signup and view all the answers

What is the impact of enzymes on reaction rates?

They increase reaction rates by a factor of up to about 1014 to 1016. Signup and view all the answers

Which statement about enzyme consumption in reactions is true?

Enzymes are not consumed during the course of the reaction. Signup and view all the answers

What are cofactors in relation to enzymes?

Cofactors may be inorganic ions, coenzymes, or organometallic groups. Signup and view all the answers

What happens to enzyme activity when its structure is denatured?

Enzyme activity is decreased or destroyed. Signup and view all the answers

Which of the following statements about enzyme localization is accurate?

Enzymes in the same metabolic pathways are often compartmentalized together. Signup and view all the answers

How do cofactors influence enzyme functions besides catalysis?

They can influence the enzyme's tertiary structure. Signup and view all the answers

What is the difference between an apoenzyme and a holoenzyme?

An apoenzyme is an enzyme without a cofactor, while a holoenzyme includes the cofactor. Signup and view all the answers

What does one International Unit (IU) of an enzyme represent?

The amount that catalyzes the formation of one micromole of product in one minute Signup and view all the answers

How is specific activity defined?

Units of enzyme activity per milligram of protein Signup and view all the answers

What happens to specific activity after purification of an enzyme?

It increases as the enzyme becomes more pure Signup and view all the answers

How is enzyme activity affected by changes in environmental conditions?

Enzyme activity is sensitive to pH, temperature, and ionic strength Signup and view all the answers

Why might a low activity enzyme require more total amount for the same reaction rate as a high activity enzyme?

To compensate for the slower reaction rate of low activity enzymes Signup and view all the answers

What is an isoenzyme?

A different form of an enzyme that catalyzes the same reaction Signup and view all the answers

Which of the following statements is true regarding the relationship between total amount of enzyme and specific activity?

Low total amount of enzyme can indicate higher specific activity Signup and view all the answers

In order to express enzyme activity, which of the following is crucial to denote?

The specific assay conditions used Signup and view all the answers

Study Notes

Enzymes

Proteins that act as biological catalysts.
Accelerate reaction rates for up to 10^14 to 10^16 times.
Reduce or prevent generation of unwanted by-products.
Work in an organized sequence to produce specific products.
Not consumed during the reaction.
Cannot change the free energy of a reaction.

Enzyme Properties

Molecular weight ranges from 12,000 to over 1 million Da.
Requires native protein conformation for catalytic activity.
Localization is important, with enzymes within the same pathways often compartmentalized together.
Compartmentalized to prevent unwanted activity.

Cofactors

Additional components required for catalytic activity.
Include inorganic ions, coenzymes, and organometallic groups.
Apoenzyme + cofactor = holoenzyme.
Assist in reactions by forming covalent interactions with substrate.
Oxidation-reduction with unique functional groups that accept or donate electrons.
Can influence enzyme tertiary structure.

Measuring Enzyme Activity

One International Unit (IU):
- The amount of enzyme that catalyzes the formation of one micromole of product in one minute (1 U = μmol/min).
- Conditions of the assay must be specified because enzymes are sensitive to pH, temperature, and ionic strength.
Specific activity:
- Units of enzyme activity per milligram of protein in a sample.
- A measure of enzyme purity.

Isoenzymes

Different forms of an enzyme that catalyze the same chemical reaction.
May vary in:
- Sub-cellular location.
- Tissue distribution.
- Kinetic properties (affinity for substrates and inhibitors, regulatory properties, and cofactors used).
Can be useful diagnostic markers for tissue damage.

Creative Kinase (CK) Isoenzymes

Found in different tissues:
- CK1 – BB (brain).
- CK2 – MB: (cardiac).
- CK3 – MM: (muscle).
Measured in blood to diagnose tissue damage
- Elevated CK2-MB levels suggest heart damage.
- Skeletal muscle and brain have different isoforms.

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Description

This quiz explores enzymes, their roles as biological catalysts, and their properties. It covers aspects such as the importance of protein conformation, the role of cofactors, and the specific characteristics that enable enzymes to function effectively. Test your knowledge on these essential biological molecules!