Fungal Physiology

Read Also

Observations: Nearly all organisms require a source of chemicals to provide energy for maintenance and growth. Of these organisms, nearly all rely upon some kind of carbohydrate. Textbooks indicate that glucose and fructose are found along the glycolytic pathway. In the absence of oxygen, yeasts utilize the alcoholic fermentation pathway to produce energy (in ATP), ethyl alcohol, and carbon dioxide. Of these products, carbon dioxide is a gas and can be measured volumetrically as you did in Durham tubes.

Question: What type of carbohydrate might serve as the best energy fuel for an organism?

Hypothesis: Yeast make the enzymes required for fermentation of all of these carbohydrates.

Prediction: If the hypothesis above is true, then carbon dioxide gas should accumulate equally among yeast samples when given each of the carbohydrates.

Experiment: Each 15 mL graduated centrifuge with four 15ga needle holes in its lid will be filled with a mixture of 7.5 ml yeast suspension (Saccharomyces cerevisiae) with 7.5 ml of 5% carbohydrate solution (or water control). Each labeled tube should be completely full. The lids should be twisted on securely. The four tubes will be inverted in a 400 mL beaker that contains water dipped from the 40°C water bath. The beaker will be placed in the water bath and observed occasionally. Time for all the tubes will be stopped when the tube with the most gas has a meniscus at about the 10 mL mark (record time in minutes).

Results: Record the bottom of the meniscus (or the bottom of any “foam”):

Carbohydrate Treatments	5% Sucrose	5% Glucose	5% Lactose	Distilled Water
Time = 0
___/60 hr

Analysis: Calculate a rate for each treatment = =

Units   Rate (     /     )

Decision:

The hypothesis above is   rejected    not rejected  

Conclusions:

The yeast cells   had    had not   used up their initial substrate.

The yeast cells   did    did not   produce invertase.

The yeast cells   did    did not   produce lactase.