12. Microbial Metabolism

Which of the following are examples of the functions of enzymes?

a) A lactase enzyme breaking down lactose sugar in the small intestine.

b) A DNA polymerase enzyme synthesizing new strands of DNA.

c) A lipase enzyme breaking down fats (lipids) in the small intestine.

d) A helicase enzyme unraveling DNA so it can be replicated.

e) All of the above.

Which characteristics are likely associated with an enzyme isolated from a human stomach where conditions are strongly acidic.

a) An enzyme that functions properly at 70 degrees Fahrenheit and at a neutral pH.

b) An enzyme that functions properly at 98 degrees Fahrenheit and at an acidic pH.

c) An enzyme that functions properly at 98 degrees Fahrenheit and at a neutral pH.

d) An enzyme that functions properly at 70 degrees Fahrenheit and at an acidic pH.

Bacteria use the enzyme urease to obtain nitrogen in a form they can use from urea in the following reaction:

What purpose does the enzyme serve in this reaction? What type of reaction is this?

Define and explain the importance of each of the following:

a. Catalase

b. Hydrogen peroxide

c. Peroxidase

d. Superoxide radical

e. Superoxide dismutase

An organism that has peroxidase and superoxide dismutase but lacks catalase is most likely an

a. aerobe.

b. aerotolerant anaerobe.

c. obligate anaerobe.

Suppose you inoculate three flasks of minimal salts broth with E. coli. Flask A contains glucose. Flask B contains glucose and lactose. Flask C contains lactose. After a few hours of incubation, you test the flasks for the presence of ß-galactosidase. Which flask(s) do you predict will have this enzyme?

a. A

b. B

c. C

d. A and B

e. B and C