Homework chapter 22 - 25 (Due April 17th)

(Yoli) page 182 Question 1 - 4
It's done!



(Indy) Page191 question 1 

Distinguish between respiration and fermentation

In Fermentation an organic substrate serves as the final acceptor; whereas in respiration, either inorganic ion are (anaerobic) or oxygen is the final electron acceptor (aerobic).

(Indy) page 192 question 2 and 3   

2) Do all microorganisms use pyruvic acid in the same way? Explain

No, they do not. Metabolism of pyruvate is not the same for all microorganisms. A variety of end products results define their different fermentative capabilities

3)Describe a pathway used for the degradation of carbohydrates by strict anaerobes
Anaerobic organisms break down carbohydrates using the pentose-phosphate pathway. Glycolysis is used by aerobic and anaerobic organisms in energy production.

(Yaneli) page 192 question 4 and  5





4. From your experiment data, you know that P. aeruginosa did not utilize any of the carbohydrates in the test media. In this view of this how do these organisms generate energy to sustain their viability?
It may be using acetate, which is not a carbohydrate and ammonium, or some other simple organic compounds that are present in the agar, without needing to utilize the more complex carbohydrates in the test media. Regardless, it utilizes these compounds via aerobic metabolism and that is how it generates the energy it needs to sustain their viability.

5. Clostridium perfringers, an obligate anaerobe, is capable of utilizing the carbohydrates released from injured tissues as an energy source. During the infectious process, large amounts of gas accumulate in the infected tissues. Would you expect this gas to be CO2? Explain.
Probably not expect carbon dioxide to be produced as a consequence of carbohydrate fermentation, but in reality, this does occur because Clostridium has a varied fermentation pathway, some of which produces carbon dioxide.

(Yanel) page 201 question 1 
1. Explain the function of the 0.1% agar in the nitrate medium.
It makes the media semi solid, which selects the organisms that are anaerobic, which is required for nitrate reduction.

(Lupe) page 202 question 2 – 5

2. Explain the functions of Solutions A and B

they show whether nitrate reduction occurred by turning red. If no color change then nitrate has remained the same.

3. If a culture does not undergo a color change on the addition of Solutions A and B, explain how you would interpret this results.

1- Nitrates were not reduced

2- Nitrates were reduced beyond the nitrite stage to ammonia or molecular nitrogen

4. Explain why the development of a red color on the addition of zinc is a negative test

Since zinc reduces nitrates to nitrites, a pink or red color will appear and verifies the fact that nitrates were not reduced to nitrites by the bacteria (a negative test).

5. Discuss the relationship between an organism’s ability to reduce nitrate past the nitrite stage and the organism’s proteolytic acitibity.

It means that the bacteria had such an active nitrate reductase it reduced the nitrate to ammonia and molecular nitrogen gas. As a result it has a very fast metabolism for nitrate.