Question

METABOLISM (FERMENTATION)							What are the expected results/did you get them.
Tube	A	B	C	Initial Reading	Final Reading	Volume of the gas bubble created	If not why and Explain
1	5 ml phosphate buffer	1 5 ml phosphate buffer	5 ml yeast	1mL	1.5mL	0mL
2	5 ml phosphate buffer	5 ml glucose	5 ml yeast	1.5mL	6.5mL	5mL
3	5 ml of 0.1 M MgSO4	5 ml glucose	5 ml yeast	1mL	8mL	7mL
4	5 ml of 50 mM EDTA	5 ml glucose	5 ml yeast	1mL	6mL	5mL
5	5 ml of 100 mM EDTA	5 ml glucose	5 ml yeast	1.5mL	2.5mL	1mL
6	5 ml of 250 mM EDTA	5 ml glucose	5 ml yeast	1mL	1mL	0mL
7	5 ml pyruvate/EDTA	5 ml glucose	5 ml yeast	1mL	8.5mL	7.5mL
8	5 ml phosphate buffer	5 ml of 0.1 M lactose	5 ml yeast	1mL	2mL	1mL
9	5 ml phosphate buffer	5 ml of 0.1 M galactose	5 ml yeast	1.5mL	2mL	0.5mL

Complete the last coloumn and state why these reactions occured. For example, in tube 3, there was a larger gas bubble because there was a presence of magnesium ions which meant the enzyme elonase was able to function.

Answer 1

• Fermentation pathway in yeast converts glucose to CO2 which is measured as gas bubble formation in the tubes.
• In the 1st tube only phosphate buffer is there no carbohydrates. Hence this must be a control. So no gas bubble.
• In 2nd tube carbohydrate is there , so glucose converted to co2 . Gas bubble formation.
• In 3rd tube glcose + mg2+ is present. Presence of Mg+2 speeds the fermentation process and hence the volume of gas bubble is large.
• In 4th, 5th and 6th tubes EDTA is present along with Glucose . the concentration of EDTA increases in each tube and the gas bubble formation decreases in each tube respectively. This is because presence of EDTA chelates the ions responsible for growth of yeast like zinc, iron etc. thus fermentation process is inhibited . So as EDTA concentration incraeses, gas bubble decreases respectively in each tube.
• Pyruvate fermentation is different pathway and hence co2 is formed.
• Yeast does not have enzymes to break lactose and galactose and hence the formation of co2 is low or nil in last 2 tubes.