Enzymes Overview Quiz

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Questions and Answers

What is the primary function of enzymes in biological reactions?

To increase the activation energy

To eliminate reactants from the reaction

To change the temperature of the reaction

To decrease the activation energy (correct)

Which of the following statements about enzymes is NOT true?

Enzymes are consumed in reactions (correct)

Enzymes can be denatured

Enzymes are usually proteins

Enzymes require cofactors for activity

How are enzymes typically named?

Based on their size and structure

Using random numerical codes

According to their substrate and function (correct)

By the temperature at which they work best

What term is used to describe the substances that enzymes act upon?

Substrates Signup and view all the answers

What suffix is commonly added to the names of enzymes that act on specific substrates?

-ase Signup and view all the answers

What is the primary function of oxidoreductases?

To transfer electrons or hydride ions Signup and view all the answers

Which type of enzyme is primarily responsible for hydrolysis reactions?

Hydrolases Signup and view all the answers

How does the active site of an enzyme relate to its substrate?

It has a specific 3-dimensional shape that matches the substrate Signup and view all the answers

What occurs when an enzyme binds to its substrate?

An enzyme-substrate complex is formed Signup and view all the answers

What model describes the precise fit of the substrate into the enzyme's active site?

Lock-and-key model Signup and view all the answers

Which class of enzymes is involved in forming bonds by condensation reactions coupled with ATP cleavage?

Ligases Signup and view all the answers

What is the role of coenzymes and prosthetic groups in enzyme action?

They are essential for enzyme activation Signup and view all the answers

What is the main change that occurs in the induced fit model of enzyme action?

The enzyme and substrate change shape for a better fit Signup and view all the answers

What is a coenzyme?

A non-protein organic substance loosely attached to enzymes. Signup and view all the answers

What happens to enzyme activity as the temperature increases?

It consistently increases until a certain temperature. Signup and view all the answers

What is the effect of substrate concentration on enzyme activity?

It increases until the enzyme reaches saturation. Signup and view all the answers

What is the role of covalent modification on enzyme activity?

It can alter the enzyme structure, increasing activity. Signup and view all the answers

Which of the following descriptions apply to zymogens?

They are inactive precursors to enzymes. Signup and view all the answers

What is the optimum pH range for pepsin?

1-2 Signup and view all the answers

According to the Michaelis-Menten model, what occurs at low substrate concentration?

The reaction is first order. Signup and view all the answers

Which of the following metal ions is NOT listed as an activator for enzymes?

Na+ Signup and view all the answers

What happens to the velocity of an enzyme-catalyzed reaction at high substrate concentrations?

Velocity becomes independent of substrate concentration. Signup and view all the answers

What does the Michaelis constant (KM) represent?

The substrate concentration at half maximal velocity. Signup and view all the answers

How do competitive inhibitors affect the Michaelis-Menten curve?

They intersect the curve at the Y-axis. Signup and view all the answers

What is the result of enzyme regulation when substrate levels are low?

Enzyme production is turned off to conserve energy. Signup and view all the answers

In a Lineweaver-Burk plot for non-competitive inhibition, what is observed?

The plots are parallel. Signup and view all the answers

What role does feedback control play in enzyme regulation?

It inhibits an early reaction in the enzyme chain when the product accumulates. Signup and view all the answers

Why are proenzymes produced in their inactive form?

To prevent accidental digestion of proteins. Signup and view all the answers

What characterizes a hyperbolic curve in enzyme kinetics?

It reflects saturation of active sites at high substrate concentrations. Signup and view all the answers

What happens when a regulator binds to an allosteric enzyme?

It alters the shape of the active site to affect enzyme activity. Signup and view all the answers

Which condition results in the maximum velocity (Vmax) in an enzyme-catalyzed reaction?

When all enzyme active sites are occupied by substrate. Signup and view all the answers

Which type of inhibition occurs when a final product inhibits the first enzyme in a series of reactions?

Feedback inhibition Signup and view all the answers

Why is it inefficient for cells to produce enzymes continuously at low substrate levels?

It wastes energy without benefit to the cell. Signup and view all the answers

How is trypsinogen activated from its inactive form?

A part of its polypeptide chain is removed. Signup and view all the answers

Which of the following statements correctly defines allosteric regulation?

Allosteric regulation alters enzyme shape without using the active site. Signup and view all the answers

Which of the following is NOT an example of a proenzyme?

Amylase Signup and view all the answers

What is the function of a regulator in allosteric enzyme regulation?

To modulate the enzyme action either positively or negatively. Signup and view all the answers

Study Notes

Enzymes

Biological catalysts that speed up chemical reactions by a factor of 10^6 to 10^12 times
Most are proteins
Named after the substrate they act on, ending in '-ase' (e.g., amylase, protease), or '-in' (e.g., pepsin, papain)

Characteristics of Enzymes

Not consumed in the reaction
Highly specific, interacting with specific substrates
Recognize, bind, and modify substrates
Large molecules composed of amino acid chains linked by peptide bonds
Can be denatured and precipitated by specific reagents (salts, solvents, etc.)
May require cofactors (non-protein molecules) for their activity

Classes of Enzymes

Oxidoreductases: Transfer electrons (hydride ions or H atoms)
Transferases: Move functional groups between molecules
Hydrolases: Break down molecules by adding water
Lyases: Add groups to double bonds, or form double bonds by removing groups
Isomerases: Rearrange atoms within a molecule to create isomers
Ligases: Join two molecules together, often using energy from ATP

How Enzymes Work

Enzymes have specific 3D shapes that fit their substrates
The active site on the enzyme binds the substrate
Forms an enzyme-substrate complex, lowering activation energy
After the reaction, the product is released and the enzyme can bind another substrate

Models of Enzyme Action

Lock-and-Key Model: Substrate's shape precisely fits the enzyme's active site
Induced Fit Model: Enzyme changes shape slightly to accommodate the substrate for optimal fit

Active/Inactive Forms of Enzymes

Apoenzyme: Inactive enzyme without its cofactor
Coenzyme: Non-protein organic molecule loosely bound to the apoenzyme
Prosthetic Group: Organic molecule tightly bound to the apoenzyme
Metal Ion Activator: Inorganic ions that assist in enzyme activity (e.g., K+, Fe2+, Ca2+)
Zymogen or Proenzyme: Inactive precursor of an enzyme, activated by removing a portion of its polypeptide chain

Factors Affecting Enzyme Activity

Temperature: Increases reaction rate up to an optimum temperature, then denaturation occurs at higher temperatures
pH: Enzymes have a specific pH range for optimal activity, outside of which they can denature
Enzyme Concentration: Higher concentration, faster reaction rate
Substrate Concentration: Increases reaction rate up to saturation point, where all active sites are occupied
Covalent Modification: Phosphorylation or methylation can alter enzyme activity
Inhibition: Competitive, non-competitive, or uncompetitive inhibitors affect enzyme activity
Allosteric Effects: Regulatory molecules bind to an allosteric site, altering enzyme shape and activity

Enzyme Regulation

Feedback Control: Products of a reaction pathway can inhibit earlier enzymes in the pathway, preventing overproduction
Proenzyme Activation: Inactive proenzymes are activated when needed (e.g., trypsinogen to trypsin)
Allosteric Regulation: Binding of regulatory molecules at allosteric sites can either activate or inhibit enzyme activity

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Description

Test your knowledge on enzymes, the biological catalysts that accelerate chemical reactions. This quiz covers their characteristics, classes, and the roles they play in biochemical processes. Perfect for students studying biology or biochemistry!