Question

What is catalase?

What reaction does catalase catalyze (i.e., what molecule does it break down, and what is it broken down into)?

Catalase breaks down toxic oxygen metabolites (such as H2O2), why is this important?

Where do these toxic oxygen metabolites come from?

Do anaerobes have catalase? Explain.

What will you observe if you add hydrogen peroxide (H2O2) to catalase-positive bacteria?

What will you see if it is catalase-negative?

What type of bacteria are catalase-positive (aerobes, anaerobes, or facultative anaerobes – note, it may be more than one type)?

What molecule do they use as the terminal electron acceptor during respiration?

What type of bacteria are catalase-negative (aerobes, anaerobes, or facultative anaerobes – note, it may be more than one type)?

What other organisms (aside from bacteria) produce catalase?

Answer 1

1. Catalase is an enzyme which is found in nearly all organisms exposed to oxygen and catalyzes the reduction of hydrogen peroxide.

2. It brings about the reaction in which hydrogen peroxide is decomposed to water and oxygen and can be written as:

2 H₂O2 (catalase)  ? 2 H₂O + O₂

3. Oxidative damage can occur when cells or other molecules in the body come into contact with hydrogen peroxide. To prevent such damage, the catalase enzyme helps getting rid of it by breaking up hydrogen peroxide (H₂O₂) into harmless water and oxygen.

4. Hydrogen peroxide is produced by reactions in our bodies. In our body various biochemical reactions take place and the hydrogen peroxide is produced as a by-product in these reactions.

5. The enzyme, catalase, is produced by bacteria that respire using oxygen, and protects them from the toxic by-products of oxygen metabolism. Catalase-positive bacteria include strict aerobes as well as facultative anaerobes but obligate anaerobes produce these enzymes in very small quantities, or not at all.

6. If an organism can produce catalase, it will produce bubbles of oxygen when hydrogen peroxide is added to it. Bubbles will be produced because O₂ is produced in the reaction.