Introduction Flashcards
Why study yeast?
- Economically important
- Cellular processes very similar to higher eukaryotes
- Well-defined genetic system
What medium allows fastest growth for yeast?
Glucose, and YPD medium, contains yeast extract, peptone, double-distilled water
What sugars can yeast not utilise?
Pentose sugars e.g. xylose
What conditions does yeast best grow in?
Aerobic
What is ergosterol?
The major fungal membrane sterol, regulates membrane fluidity, plasma membrane biogenesis and function
In presence of high concentrations of glucose, how would its growth be described?
(Always) Fermentative
What is an example of a carbon source that is non-fermentative?
Glycerol
What is the fermentation process?
Draw it
Describe the Pasteur effect
When oxygen (and glucose conc.) is limited, sugar metabolism is stimulated. When oxygen increases, ATP and citrate production increases, and rate of glycolysis slows. ATP and citrate act as allosteric inhibitors for phosphofructokinase (enzyme in glycolysis).
Describe the Crabtree effect
In high concentrations of glucose, respiration is inhibited. The degradation of glucose proceeds by fermentation only, and there is no Pasteur effect. Here, synthesis of mitochondria and respiratory machinery are repressed
What three forms can yeast exist in?
Haploid, 2 mating types (a and alpha); diploid
Draw the life cycles of S. cerevisiae and Schiz. pombe
d r a w
What is the difference between a budding yeast and fission yeast?
Budding: the original, mother cell gives rise to a daughter cell made entirely of new cell surface material
Fission: the initial cell enlarges and then pinches off into 2 daughter cells
What are the main differences between industrial and lab strains of yeast?
Industrial: usually polyploid or aneuploid, mate and sporulate poorly, may be homothallic, may be hybrids between S. cerevisiae and other yeast
Lab: usually haploid (sometimes diploid), display good mating and sporulation capability, usually heterothallic
What is meant by homothallic and heterothallic?
Homothallic = possesses male and female reproductive structures on the same thallus, capable of sexual reproduction from a single organism Heterothallic = requires 2 compatible partners to produce sexual spores (most yeasts, including S. cerevisiae)
