AhmadWeek3: Difference between revisions

Latest revision as of 22:22, 7 February 2013

Saccharomyces cerevisae, a type of yeast, uses ammonia as its primary nitrogen source
- Past research has shown that ammonia concentration affects growth
- In this paper, the researches wanted to know if ammonia flux, and not concentration, is the limiting factor
Physiological Parameters
- S. cerevisae was first grown in cultures with different levels of ammonia, but fixed glucose concentrations
- Increases in the ammonia concentration from 29 to 61 mM showed a change in biomass from 4.9 to 8.2 g/L
- After 61 mM, however, there was no significant increase in biomass
- Formula to calculate ammonia flux: [dilution x (input ammonia concentration - residual ammonia concentration)/biomass]
- At a level above 44 mM, oxygen consumption was equal to carbon dioxide production
Ketoglutarate, Glutamate, Glutamine concentrations as ammonia concentrations were increased
- Ketoglutarate: Decreased
- Glutamate: Increased
- Glutamine: Increased
Figure 1
- X axis: NH4 concentration
- Y axis:
  - A: Residual NH4 concentration
  - B: 02 consumption/CO2 production
  - C: Ketoglutarate, Glutamate, Glutamine concentrations

Northern Analyses are RNA analyses that were done to see how the changes in nitrogen affect nitrogen-regulated genes
Figure 2 shows gene expression in response to different levels of NH4 concentrations
- X axis: NH4 concentration
- Y axis: Gene expression
Permease-encoding genes:
- GAP1
- PUT4
Biosynthetic genes
- ILV5
- HIS4
- GDH1
- GLN1

Figure 3 shows enzyme activity at different NH4 concentrations
- X axis: NH4 concentration
- Y axis: Enzyme activity
Enzymes Studied:
- NADPH
- NAD-DGH
- GS Transferase
NADPH activity consistently decreased with increased NH4
NAD-GDH activity consistently increased with increased NH4
GS Transferase and Synthetase decreased slightly until 60 mM, but then leveled off with increased NH4
The conclusion of the paper is that that the nitrogen metabolism of S. cerevisiae is regulated by ammonia concentration
- The species may have an ammonia sensor

Flux: "The total amount of a quantity passing through a given surface per unit time."
Permease:"General term for a membrane protein that increases the permeability of the plasma membrane to a particular molecule, by a process not requiring metabolic energy."
Oligonucleotide: "Linear sequence of up to 20 nucleotides joined by phosphodiester bonds."
Gram-negative:"This is a primary characteristic of bacteria that have a cell wall composed of a thin layer of peptidoglycan covered by an outer membrane of lipoprotein and lipopolysaccharide containing endotoxin."
Gram-positive:"This is a primary characteristic of bacteria whose cell wall is composed of a thick layer of peptidologlycan containing teichoic and lipoteichoic acid complexed to the peptidoglycan."
Glutamate:"Major fast excitatory neurotransmitter in the mammalian central nervous system."
Glutamine:"A crystalline amino acid occurring in proteins; important in protein metabolism.One of the 20 amino acids that are commonly found in proteins."
Isomerase:"An enzyme that converts molecules into their positional isomers."
Synthetase:"Enzymes of class 6 in the e classification, catalyse synthesis of molecules, their activity being coupled to the breakdown of a nucleotide triphosphate."
Metabolite:"Any substance produced by metabolism or by a metabolic process."

==Assignments==

@@ Line 54: / Line 54: @@
 #[http://www.biology-online.org/dictionary/Glutamate Glutamate]:"Major fast excitatory neurotransmitter in the mammalian central nervous system."
 #[http://www.biology-online.org/dictionary/Glutamine Glutamine]:"A crystalline amino acid occurring in proteins; important in protein metabolism.One of the 20 amino acids that are commonly found in proteins."
+#[http://www.biology-online.org/dictionary/Isomerase Isomerase]:"An enzyme that converts molecules into their positional isomers."
+#[http://www.biology-online.org/dictionary/Synthetase Synthetase]:"Enzymes of class 6 in the e classification, catalyse synthesis of molecules, their activity being coupled to the breakdown of a nucleotide triphosphate."
+#[http://www.biology-online.org/dictionary/Metabolite Metabolite]:"Any substance produced by metabolism or by a metabolic process."
+ {{Salman Ahmad}}