Lesson 5 - Yeast Biochemistry SAQ

1.         **Answer both parts of this question.

a)    Discuss the differences in the methods used by Saccharomyces yeast to take up maltose and sucrose.

b)    Using a suitable diagram, explain the principal differences between uptake of nutrients via active transport and facilitated diffusion? How do these differ from simple diffusion?

2.         *Answer both parts of this question:        

a)      Draw an equation showing how a coenzyme takes part in a reaction in which compound A is oxidised to compound B and indicate how the coenzyme might be reduced in a subsequent biochemical reaction.

b)      ATP is the principal molecule used by cells to conserve energy. How many molecules of ATP are formed per molecule of glucose consumed via fermentation and respiration, respectively?

3.         *What is the difference between catabolism and anabolism?

4.         *Identify the two principal compounds used by yeast cells to store carbohydrates and indicate their primary functions.

5.         **Your brewery wishes to increase its fermentation capacity and has decided on a dual approach of installing some new vessels with a capacity of 5000 hL, twice as big as currently used. In addition, it has been decided to increase the gravity of the wort from 15 ºP to 18.5 ºP . In order to reduce pressure on the brewhouse, which is not being upgraded, the increase in wort gravity will be via the addition of glucose syrup added directly to the current all-malt wort on the hot side of the paraflow. The brewhouse regime is not planned to be altered. The larger vessels will require six batches of wort, as opposed to three, and will increase the fill time from eight to fifteen hours. Pitching rates and wort oxygenation will be increased pro rata to allow for the increase in wort concentration. All yeast will be pitched at the start of addition of the first batch of wort.

Using your biochemistry knowledge of the growth of yeast in wort, what are the potential problems with this plan?