Lesson 3 - Yeast Morphology and Evaluation SAQ

1. * Some of the following statements are true; others are not. Indicate which statements are true. Then indicate which statements are false and explain why they are false.

a)    Aneuploid yeast cells contain more than one copy of the nucleus.

b)    Prokaryotic cells do not have a defined nucleus.

c)    The whole of the yeast genome is contained in the 14 nuclear chromosomes.

d)    Brewing strains of yeast have been selected because they all have very stable genomes.

e)    Lager strains are hybrids of two different yeast strains, one being an ale strain, S. cerevisiae; the other is a wild yeast belonging to the species, S. eubayanus.

f)     Brewing yeast cells reproduce by binary fission.

2. * Describe the main functions of the following yeast organelles:

a)    Periplasm

b)    Golgi body

c)    Ribosomes

d)    Plasmamembrane

e)    Cell wall

3. ** The budding process, in which brewing yeast cells multiply, is called an asymmetric process. What does this mean, and what are its consequences?   

4. ** You use a moderately flocculent lager yeast to brew your beers. Recently, you have noticed that the solids concentration of your bottom crops has significantly decreased. Furthermore, the green beer yeast count is higher than normal. What investigations would you conduct to determine what has caused this change?

5. * Brewing yeast are mesophilic, heterotrophic facultative anaerobes. What do these terms mean?