Lesson 4 - Yeast Biochemistry
This lesson describes the biochemical pathways that explain the activities of yeast in brewing. It begins by looking at what metabolism is and how we control it. It then looks at how nutrients, including sugar, are taken up by brewing yeast. Next, it explores metabolism in more detail, focusing on sugar metabolism and looking at two particular modes of metabolism, respiratory and fermentative. Finally, it considers the need for redox control and takes a brief look at gluconeogenesis and the storage of carbohydrates in yeast.
Lesson Sign-off
In this lesson we have looked at the biochemical pathways that explain how yeast behaves in the ways that it does.
For further information you should look at any of the mainstream biochemistry text books. For detail specific to brewing and distilling the Journal of the Institute of Brewing and Distilling is a great resource.
You should now be able to:
-
Describe the carbohydrate nutrients that brewing yeasts are able to utilise and list those they cannot.
-
Describe how carbohydrates are transported into yeast cells.
-
Explain how metabolism is controlled and the effect of the ordered uptake of carbohydrates and other nutrients.
-
Illustrate the process of glycolysis, including related reactions, and discuss its role in metabolism in brewing yeast.
-
Discuss how pyruvate is metabolised and how it is used by yeast cells in the creation of biosynthetic pathways.
-
Show an understanding of the roles of oxygen and fermentable sugars in the regulation of yeast metabolism and their effect on energy generation.
-
Define and illustrate cellular redox control.
-
Explain the formation and function of glycogen and trehalose.