Biochemistry Differential Tests 2

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Questions and Answers

What is the primary function of the coagulase enzyme in S.aureus?

To facilitate nutrient absorption

To break down proteins

To cause blood clotting (correct)

To enhance cellular respiration

In the slide agglutination test, what indicates a positive reaction?

Visible clumping of cells (correct)

Formation of a smooth mixture

Change in color of the antiserum

No change in the mixture

How does the antibody recognize and interact with the antigen in S.aureus?

By binding to protein A antigen (correct)

By degrading the antigen

By promoting cell division

By altering the structure of the antigen

What laboratory procedure utilizes antiserum for testing microbial presence?

Serotyping Signup and view all the answers

What is the typical duration for reading results in a slide agglutination test?

2 minutes Signup and view all the answers

Which organism is known to produce coagulase, an enzyme that causes the clotting of blood?

Staphylococcus aureus Signup and view all the answers

What principle underlies the process of antibody-antigen interactions?

Affinity between complementary molecules Signup and view all the answers

Which serotyping technique separates bacterial strains based on their surface antigens?

Slide agglutination test Signup and view all the answers

In blood typing processes, which antigen is present in type A blood?

A antigen Signup and view all the answers

What is the primary component used in slide agglutination methodology?

Glass slides Signup and view all the answers

Which enzyme's activity can be significant for differentiating among Gram-positive cocci?

Catalase Signup and view all the answers

Which of the following statements accurately reflects the function of phenylalanine deaminase?

It converts phenylalanine into phenylpyruvic acid. Signup and view all the answers

In which medium would you expect Escherichia coli to show good growth with possible selective characteristics?

MacConkey agar Signup and view all the answers

What is the function of the coagulase enzyme produced by S. aureus?

To coat bacterial cells with plasma proteins Signup and view all the answers

Which of the following accurately describes agglutination?

Clumping of particles due to antibody interactions Signup and view all the answers

What is the main purpose of serotyping in microbiology?

To distinguish groups of closely related microorganisms by antigens Signup and view all the answers

Which blood type is correctly characterized by having both A and B antigens?

Type AB+ Signup and view all the answers

In the slide agglutination test, what role does antiserum play?

It contains antibodies that interact with antigens Signup and view all the answers

Which component initiates an antibody-mediated response in the immune system?

Antigen Signup and view all the answers

What does a negative result with no clumping in the coagulase test indicate?

Absence of S. aureus Signup and view all the answers

Which antigen is associated with the lipopolysaccharide in bacteria?

O antigen Signup and view all the answers

Study Notes

Differential Tests 2

Differential tests are used to identify microorganisms based on their biochemical reactions.
Each assay is used to determine if an organism possesses a specific enzyme.
For each assay, the following information should be noted:
- Name of the assay
- Input(s) and Output(s)
- Specific enzyme(s)
- Reagents/pH indicator
- Principle of the test
- Positive and negative results

Biochemistry 2

Various biochemical tests are used to identify microorganisms.
Examples include tests for urease, nitrate reduction, catalase, oxidase, utilization of amino acids (phenylalanine), starch hydrolysis, gelatin hydrolysis, DNA hydrolysis, lipid hydrolysis, and blood agar.
Urea Hydrolysis: Used to identify organisms that can synthesize urease which breaks urea down into ammonia and carbon dioxide which raises the pH. pH indicator is phenol red (yellow or orange <8.4, red or fuchsia >8.4).
Nitrate Reduction: Organisms that reduce nitrate (NO3) to nitrite (NO2). Re-test with zinc dust if negative.
Catalase Production: Tests the ability of an organism to produce catalase, an enzyme that breaks down hydrogen peroxide into water and oxygen. Bubbling confirms a positive result.
Oxidase Production: Tests the presence of cytochrome c oxidase in the organism's electron transport chain. A positive result turns the reagent purple/blue.
Phenylalanine Deaminase: Test for organisms that can produce the enzyme phenylalanine deaminase to break down phenylalanine. Positive test indicated by a green color from reagents.
Starch Hydrolysis: Tests the ability of an organism to produce the enzyme amylase to break starch. A clear zone around the colonies indicates a positive result.
Gelatin Hydrolysis: Tests for the presence of Gelatinase, which digests gelatin. Organisms that produce gelatinase will liquefy the medium.
DNA Hydrolysis: Tests for the presence of deoxyribonuclease (DNase), which breaks down DNA. A clear zone around the colony indicates presence of the enzyme.
Lipid Hydrolysis: Tests for lipase, an enzyme that breaks down triglycerides. This will lower the pH and the medium will change color.
Blood Agar: Identifies hemolysis, the lysis of red blood cells (RBCs); Alpha, Beta, and Gamma are possible outcomes.
Coagulase Test: Used to identify organisms (like S. aureus) capable of producing coagulase, an enzyme that causes clotting of blood plasma.

Slide Agglutination

Used to identify microorganisms using antibodies.
Antibody: An immunoglobulin that binds to a specific antigen.
Antigen: A molecule that triggers an antibody response.
Antiserum: Blood that contains antibodies.
Agglutination: Clumping of particles due to antibody-antigen binding.
Serotyping: Differentiating closely related microorganisms by their antigens.

Lab Report Questions

Lab reports are due at the start of the next lab period for this specific differential test practice.
Refer to the protocol for specific questions related to each differential testing technique.

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Description

This quiz focuses on differential tests used in microbiology to identify organisms based on biochemical reactions. Each assay assesses the presence of specific enzymes and their corresponding biochemical processes. Topics cover tests like urease, nitrate reduction, and other enzyme assays vital for microbiological identification.