Lab 22: Hydrolysis of carbohydrates, lipids, proteins, and nucleic acids

What is the purpose of an exoenzyme?

Secreted by a cell and function outside of it to break down large, complex molecules into simpler forms to be absorbed

Which 4 plates will be used to evaluate the ability of microorganisms to break down complex molecules?

Starch agar, casein, DNA, and tributyrin

Which enzyme breaks down starch into simple sugars?

Amylases

Which plate tests for starch hydrolysis?

Starch agar

What substance is used to detect starch break down in a starch agar plate?

Iodine

In a starch agar, iodine is amber colored. What does this indicate?

Starch is not present

In a starch agar, iodine is blue-black. What does this indicate?

Starch is present

In a starch agar, what color is iodine for E. coli and what does this tell us about the organism?

Blue-black; does not have amylases

What plate tests for protein hydrolysis?

Casein agar

Which exoenzyme breaks down casein?

Proteases

What does casein produce when broken down?

Amino acids and peptides

In a casein agar, the zone is clear. What does this indicate?

Casein is not present

In a casein agar, the zone is cloudy white. What does this indicate?

Casein is present

In a casein agar, what color is the agar for E. coli and what does this tell us about the organism?

Cloudy white; does not have proteases

Which exoenzyme breaks down triglycerides?

Lipases

What does triglyceride produce when broken down?

Fatty acids and glycerol

Which plate tests for triglyceride hydrolysis?

Tributyrin agar

Which plate is used in the dairy industry to determine if lipolytic organisms are present in milk?

Spirit blue agar

What is affected when lipolytic organisms break down fats in milk?

Taste

What compounds are present in a spirit blue agar?

Peptones, tributyrin, spirit blue dye

What happens to the pH when tributyrin is broken down and why?

pH decreases because of fatty acid presence

In a spirit blue agar, a dark blue precipitate was produced. What does this indicate?

Triglyceride is not present and pH is decreased

In a tributyrin plate, a clear zone is present. What does this indicate?

Triglyceride is not present

In a tributyrin plate, the zone is uniformly opaque. What does this indicate?

Triglyceride is present

In a tributyrin plate, what color is the agar for E. coli and what does this tell us about the organism?

Uniformly opaque; does not have lipases

Which exoenzyme breaks down DNA?

DNase

What does DNA produce when broken down?

Smaller nucleic acids consisting of one to four nucleotides

Which plate tests for DNA hydrolysis?

DNase test agar

In a DNase test agar that contains methyl green, DNA, and peptide, what indicates that the DNA was broken down?

Clear zone

In a DNase test agar that contains Toluidine Blue dye, what indicates that the DNA was broken down?

Pink zone