Yeast Flashcards
What is yeast, an eukaryote or a prokaryote?
Eukaryote
What are the two phyla of yeast?
Ascomycota and Basidiomycota
Explain the mutualistic relationship between S. cerevisiae and L. sanfranciscensis?
S. cerevisiae (yeast) provide L. sanfranciscensis (bacteria) with CO2 + BVitamin while LAB provide with lactic acid
Explain the mutualistic relationship between maltose positive LB and maltose negative yeast.
Maltose negative yeast cannot absorb directly maltose. Therefore it uses LB to break down maltose into glucose and lactic acid which are then absorbed by the yeast to produce ethanol.
What are some important yeasts and their role?
- Saccharomyces cerevisiae -> baker yeast
- Saccharomyces pastorianus (close related to above)
- Schizosaccharomyce pombe -> fission yeast
- Kluyveromyces lactis -> milk yeast
What type of reproduction are possible for yeast and their respective pathways?
Vegetative: Budding or fission
Sexual: Haploid -> Type a or type alpha
Diploid
How is a zygote formed and how is are ascospores formed?
Zygote are formed with mating between type a and type alpha.
Ascospore are formed by meiosis of diploid cells.
What are the products of each respective step of the alcoholic fermentation?
Two steps.
Products
Step 1: 2 ATP, 2 NADH and 2 pyruvate
Step 2: 2 CO2, 2 NAD+ and 2 Ethanol
Can saccharomyces uptake sucrose?
No, require external enzymes to break it into glucose and fructose in order to uptake in cell.
What is the crab tree effect?
That ethanol and CO2 will be produced under anaerobic condition but also under aerobic conditions if glucose s in high concentrations.
When can glycerol as a product be produce in the glycerol biosythesis? Otherwise, which products are formed?
If aw is low glycerol will be produced. If not then ethanol and CO2 will be produced.
What are the enzymes responsible for glycerol formation in the glycerol biosynthesis?
Gdp p and Gpp p enzymes.
What are fusel alcohols?
Alcohols with more than 2 carbon atoms
Describe the ehrlich pathway
An AMINO ACID goes through TRANSAMINATION to an alpha-KETO ACID which is then DECARBOXYLATED to CO2 and a FUSEL ALDEHYDE.
If O2 present (oxidation) -> fusel acid
if O2 not present (reduction) -> fusel alcohol
Diketone are flavor defects as they have buttery flavor (in beer not appreciate but in cheese yes). This compound is derived from intermediates of which amino acids?
Valine and isoleucine amino acids.
