Clinical Chemistry I - Week 12 Quiz

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Questions and Answers

What is the role of a cofactor in enzyme activity?

It binds to the active site of the enzyme.

It is required for maximum enzyme activity. (correct)

It acts as the substrate for the reaction.

It denatures the enzyme to enhance its activity.

What is the function of the allosteric site on an enzyme?

To serve as the primary site where the enzyme's activity is regulated. (correct)

To increase the enzyme's temperature stability.

To bind the substrate directly.

To release the products of the reaction.

Which of the following describes an apoenzyme?

A type of enzyme that is not active.

The overall functional unit of an enzyme.

The protein portion of the enzyme without its cofactor. (correct)

A non-protein substance required for enzyme activity.

Which of the following is an example of an inorganic cofactor?

Chloride ions Signup and view all the answers

What is the systemic name for lactate dehydrogenase?

NAD+ oxidoreductase Signup and view all the answers

What role do enzymes serve in relation to diseases?

Enzymes can act as a marker of cell death. Signup and view all the answers

Which method is preferred for testing enzyme activity?

Continuous monitoring method Signup and view all the answers

During an enzyme test, what condition is crucial for the reaction to occur optimally?

Incubation at 37ºC Signup and view all the answers

What is the main challenge in isolating and measuring enzymes?

Difficult to isolate and measure the enzyme itself due to low concentration. Signup and view all the answers

Which method can quantify enzyme concentration by mass?

Immunoassay methodologies Signup and view all the answers

What is the primary function of enzymes in the cell?

To act as catalysts Signup and view all the answers

Which of the following best describes the specificity of enzymes?

Enzymes are highly specific for their substrate Signup and view all the answers

What term is used for enzymes that have different structures but catalyze the same reaction?

Isoenzymes Signup and view all the answers

Which factor is NOT a condition for optimal enzyme activity?

Pressure Signup and view all the answers

How are enzymes commonly tested in a laboratory setting?

Using fixed time and continuous monitoring assays Signup and view all the answers

What is the standard suffix added to enzyme names that react with their substrates?

ase Signup and view all the answers

What is NOT a significant consequence of genetic diseases with enzyme system defects?

Enzyme overproduction Signup and view all the answers

What is the primary role of feedback control in enzyme activity?

To inhibit or activate enzyme production based on needs Signup and view all the answers

What is the primary role of enzymes in chemical reactions?

To lower the activation energy Signup and view all the answers

How many molecules of substrate can a typical enzyme catalyze per second?

1 to 10,000 Signup and view all the answers

What forms when an enzyme binds to its substrate?

An enzyme-substrate complex Signup and view all the answers

What type of reaction involves the synthesis of compounds?

Anabolic reactions Signup and view all the answers

What is the role of R-groups in the enzyme's active site?

To help the substrate bind Signup and view all the answers

Which factor does NOT affect enzyme action?

Color of the substrate Signup and view all the answers

What happens to the shape of the enzyme during the reaction process?

It adjusts to improve catalysis Signup and view all the answers

What type of reaction involves breaking down compounds?

Catabolic reactions Signup and view all the answers

At what temperature do most enzymes in humans exhibit peak activity?

37°C Signup and view all the answers

What happens to an enzyme's activity at extreme pH levels?

It loses activity. Signup and view all the answers

Which type of enzyme inhibitor binds to the active site?

Competitive inhibitor Signup and view all the answers

When does the rate of reaction become dependent only on enzyme concentration?

When substrate concentration exceeds enzyme concentration. Signup and view all the answers

What is the effect of increasing substrate concentration on reaction rate?

It increases the rate until the maximum activity is reached. Signup and view all the answers

What is a common cause of enzyme denaturation?

High temperature Signup and view all the answers

What describes the action of noncompetitive inhibitors?

They bind to a site other than the active site. Signup and view all the answers

In what pH range do most physiological enzymatic reactions occur?

7.0 - 8.0 Signup and view all the answers

What is the primary disadvantage of the Fixed-Time Method in measuring enzyme activity?

It will not notice deviations from linearity. Signup and view all the answers

Which statement correctly describes the Continuous Monitoring Method for enzyme activity measurement?

It involves taking measurements at specific time intervals or continuously. Signup and view all the answers

What is defined as one international unit (IU) of enzyme activity?

The amount of enzyme that catalyzes the reaction of 1μmol of substrate under specified conditions per minute. Signup and view all the answers

How is enzyme concentration typically expressed in clinical settings?

In international units per liter (IU/L or U/L) Signup and view all the answers

Which enzyme is considered a clinically significant liver enzyme?

Alanine Aminotransferase Signup and view all the answers

In the use of enzymes as reagents, which substance can be measured using hexokinase?

Glucose Signup and view all the answers

Which of the following is NOT classified as a cardiac enzyme?

Amylase Signup and view all the answers

Which enzyme is associated with the digestion of fats?

Lipase Signup and view all the answers

Study Notes

Clinical Chemistry I - Week 12: Enzyme Properties and Reaction Influencing Factors

Course: Clinical Chemistry I
Course Code: 0202304
Instructor: Mohammad Qabajah
Textbook: Tietz Fundamentals of Clinical Chemistry and Molecular Diagnostics (8th ed.) by Rifai, Horvath, & Wittwer (2019)

Objectives

Define enzymes and their structural components.
Discuss enzyme characteristics, naming, and classification.
Explain enzyme activity and influencing factors.
Compare substrate-enzyme complex formation theories.
Differentiate first-order and zero-order kinetics.
List clinically significant enzymes by name and abbreviation.
Explain enzyme testing methods (fixed time and continuous monitoring).
Discuss simplified enzyme activity measurement procedures.
Identify abnormal enzyme results (low, normal, high) and possible diagnoses based on results.

Definition of the Enzyme

Large protein substances in cells (catalysts, not consumed).
Highly specific for their substrate.
Optimal conditions for activity (temperature, pH, etc.).
2,000-3,000 different enzymes in each cell.
Involved in multi-step biochemical pathways.
Regulated through feedback control.
Isoenzymes (isozymes) catalyze the same reactions but differ structurally.
Production directly controlled by genes; genetic diseases can affect enzyme systems.

Enzyme Nomenclature

Standardized by the Enzyme Commission (EC) of the International Union of Biochemistry (IUB).
Suffix "ase" added to the name (e.g., Lactase).
Suffix "in" added when the compound is digested (e.g., Pepsin).
Each enzyme has a recommended name, abbreviation, and EC code number.

Enzyme Composition and Structure

Enzymes are distinguished from other proteins by their catalytic activity.
Any structural change can affect catalytic activity.
Holoenzyme: Complete enzyme with all parts.
- Apoenzyme: Protein portion of the enzyme.
- Cofactor: Non-protein substance (activator or coenzyme).
Catalytic Site (Active Site): Region that binds the substrate.
Substrate: Substance acted upon by the enzyme in a chemical reaction.
Allosteric Site: Enzyme cavity not the active site, often for regulation.

Enzyme Cofactors

Non-protein substances help enzymes reach maximal activity.
Two types of cofactors:
- Inorganic cofactors (activators): Examples: chloride ions, magnesium ions.
- Organic cofactors (coenzymes): Derived from vitamins; examples: NAD, NADH, NADP, NADPH.
- Prosthetic group: Organic cofactors tightly bound to the enzyme.

Enzyme Reaction: Example

L-lactate + NAD → Pyruvate + NADH + H+ (Enzyme: LDH)
- Substrate: L-lactate
- Cofactor (Coenzyme): NAD
- Product 1: Pyruvate
- Product 2: NADH + H+

Enzyme Catalytic Properties

Enzymes are catalysts.
How enzymes work
- Lower the activation energy for reactions.
- Increase reaction rate without being consumed.
- Usually catalyze between 1-10,000 substrate molecules per second.

Factors Affecting Enzyme Action

Temperature: Optimum activity near physiological temperature (e.g., 37°C in humans). High temperatures denature enzymes.
pH: Optimum activity within a narrow pH range (physiological pH). Extreme pH values denature enzymes.
Enzyme Concentration: Reaction rate dependent on enzyme concentration (zero-order kinetics). Enzyme concentration limited by substrate concentration.
Substrate Concentration: Reaction rate increases with substrate concentration (first-order kinetics).
Inhibitors: Cause a loss of enzyme activity.
- Competitive: bind to active site.
- Non-competitive: bind to different site.
- Uncompetitive: bind to enzyme-substrate complex. Inhibitor is useful for medication design.

Testing of Enzymes

Enzymes are not a health problem but rather a marker of cell death.
Enzymes are present in small amounts of fluids and are used to diagnose diseases.
Easier to measure catalytic activity relative to concentration.

###Testing of Enzymes: Enzyme Activity Measurement

Procedure based on the reaction the enzyme catalyzes.
- Add substrate to the enzyme sample in a controlled environment (optimum temp, pH).
- Incubate.
- Measure products to quantify enzyme activity (using Spectrophotometer).
Fixed-Time Method: Measures reaction amount after a fixed time.
Continuous Monitoring Method (Kinetic): Measurements taken during the reaction.

Enzyme Units and Calculation

Units defined as catalyst reaction speeds (e.g., international units – IU).
Enzymes usually expressed in units per liter (IU/L or U/L).

Enzymes as Reagents

Enzymes used to measure other constituents.
Example: glucose measurement using hexokinase enzyme.

Clinically Significant Enzymes

List of clinically significant enzymes important in diagnoses.
- Liver enzymes (AST, ALT, ALP).
- Cardiac enzymes (CK-MB, LDH).
- Others (Amylase, Lipase, Acid phosphatase, etc.).

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Description

Test your knowledge on enzyme properties and the factors influencing their reactions in the context of Clinical Chemistry I. This quiz covers definitions, characteristics, kinetics, and enzyme testing methods based on the textbook 'Tietz Fundamentals of Clinical Chemistry and Molecular Diagnostics'.