BIO152: Cell Biology Lab 3 Report on Yeast Metabolism Experiment

This lab report analyzes an experiment on yeast metabolism, examining the effects of different carbon sources (glucose, pyruvate) and oxygen levels on yeast strains. The report includes a results section with a completed table summarizing data on cell concentration, ethanol production, glucose concentration, and growth time under various conditions. Observations are made on the presence of ethanol, cell concentration, glucose concentration, and growth time across different experimental conditions. Discussion questions address ethanol production, energy yield, glucose concentration, and growth time, comparing and contrasting aerobic and anaerobic metabolism in yeast. The report highlights the differences in energy yield and end products, such as ethanol production under anaerobic conditions, and discusses the role of glycolysis and fermentation in the metabolic processes of yeast. The references used in the report are also included.

BIO152 Cell Biology
Lab 3 report
STUDENT NAME: Luwam Hailemichael STUDENT NUMBER: 33173989
.
Results
Table 1: Summary of data from the experiment on yeast metabolism
Cell
concentration
cells/mL
The concentration of
Extracellular Glucose in
growth medium
mM
Growth time
of cultures
(h)
No. Carbon
source
O2
Strain Presence
of EtOH
at the
cessation of
growth (Tm)
Initial (T0) Final (Tm)
1 Glucose
+
Gr
No No
3.6 x 107 3.6 x 104 36 mM 30
+
Pe
No Yes
0.4 x 107 0.4 x 104 4 mM 20
2 Glucose
-
Gr
No Yes
0.4 x 107 0.4 x 104 4 mM 20
-
Pe
No Yes
0.35 x 107 0.35 x 104 3.5 mM 20
3 Pyruvate
+
Gr
No No
3.7 x 107 N/A N/A 30
+
Pe
No No
0 x 107 N/A N/A N/A
Observations from Table 1 for both strains grown under the three different conditions
Presence of ethanol
Ethanol plays a crucial role as a chemical stress factor which hinders cellular growth and
plays a crucial role as a metabolic factor in cells and strains, (Bleoanca et al., 2013). When
glucose was used as a carbon source at the maximum time there were changes in ethyl
hydroxide concentrations. Presence or absence of oxygen shows no effect on the
presence of ethanol in the two types of strains.
Cell concentration
The effect of the strain on cell concentration offers growth rates dependant on the use and
type of carbon source. Gr strain exhibit high cellular concentration while using glucose and
pyruvate due to an availed energy source which the strain utilizes hence allowing high
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cellular concentration. The absence of oxygen yields low cell concentration thus the limited
breakdown of energy for the strain to initiate cell proliferation.
The concentration of extracellular glucose in growth medium
The concentration of extracellular glucose in the growth medium tend to decrease due to
the usage of glucose for the various anaerobic process in the culture strains to yield
energy and ATP for use in the pyruvate processes. When more glucose is broken down
during the pyruvate process, then fewer amounts of extracellular processes are obtained in
the process.
Growth time of cultures
Cell concentration is highly achieved when the growth time of the cultures increase. The
longer duration of growth time cultures achievers higher cellular concentration of the
strains. Typical growth cells exhibit a stationary phase which it has peak hours of between
25-35 hours exhibiting higher contraction in terms of cells, (The Growth of Bacteria
Populations n.d).
Discussion questions
Observations of ethanol production across the strains under the different conditions (3mks)
Ethanol production across the different conditions varies. In pyruvate, glucose acts as the
source of energy. glycolysis provides the ATP for the culture strains which ensures that
glycolysis takes place. Glucose is broken in this phase to produce two molecules of
pyruvate which often requires four molecules of ATP to be produced. During the absence
of oxygen, the energy source is obtained through glycolysis, which is the breakdown of
glucose into the lactic acid formation, which ensures that energy is available through ATP.
Pyruvic acid is broken down into alcohol and carbon dioxide and takes place anaerobically
in the culture strains.
Observations of the resultant energy yield of resultant energy yield of cell concentration
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across the strains under the different conditions. (3mks)
Catabolic pathways often occur across living organisms, the pathways involved often
transfer energy released through the breakdown of nutrients into ATP. Cells perform
anaerobic respiration through glycolysis. The energy yield is dependent on the breakdown
of glucose and the corresponding gateway. In pyruvate, glucose is broken down so that
ethanol can be obtained. Which in glucose phase, glucose is broken down to yield ATP.
Observations of glucose concentration across the strains under the different conditions
(3mks)
During the glycolysis phase, the glucose present is broken down to lactic acid, which avails
energy to be used in form of ATP, hence the concentration tends to decrease. Hence it is
observed that under anaerobic process, the oxygen levels tend to, lower due to being used
in the breakdown process to yield the energy needed. In the pyruvic process, glucose is
used extensively in order to allow the formation of ethanol and carbon dioxide, (Glucose
and cell culture, 2018).
Observations of growth time across the strains under the different condition metabolic
pathways involved, and the resultant energy yield.
The growth time across the different strains shows that reach time is reached between 25
and 35 hours which is the typical exponential phase for maximum cell generation and
output process. Under the different conditions, the growth time of cells is generally similar
displaying a similar pattern. At the exponential phase of the strains, the cells are dividing
through binary fusion and growing is through geometric progression. The cells are dividing
at a constant rate depending on the media or carbon sources used, (Foght, 2008).
Based on these conclusions, comment on the differences in energy yield and end products
for aerobic and anaerobic metabolism in yeast. (6mks)
Degradation of glucose can be done both anaerobically and aerobically. Each of the
processes produces respiration with anaerobic respiration producing ethyl alcohol,
especially in yeast. Anaerobic cellular respiration often occurs with the production of ATP
in most cells, with its first stage being glycolysis, hence oxygen is insufficient, an organism
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which is unable to perform the anaerobic cycle undergoes alternative process if ATP
production. Glycolysis pathway produces ATP during the fermentation. The pyruvic acid is
thus reduced by NAD+ which ensures that glycolysis takes place producing ethyl alcohol,
hence its presence, (Cell process fermentation, 2018).
It is crucial to note that yeast has the ability to degrade glucose both in the presence of
oxygen and in the absence of oxygen. In each of the cases, respiration products are
carbon dioxide and anaerobic respiration produces ethyl alcohol. Anaerobic respiration
yields high energy compared to the anaerobic state. Yeast uses glucose in a slower rate to
satisfy the energy needs in presence of oxygen, while at the same time it can use much
more energy to extract small amounts of glucose molecule, (Institute of Creation
Research, 2018).
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References
Bleoanca, I., Silva, A. R. C., Pimentel, C., Rodrigues-Pousada, C., & de Andrade Menezes, R. (2013).
Relationship between ethanol and oxidative stress in laboratory and brewing yeast strains. Journal of
bioscience and bioengineering, 116(6), 697-705.
Cell process fermentation (2018). Retrieved September 21 2018. From
https://www.texasgateway.org/resource/cell-processes-fermentation
Foght, J. (2008). Anaerobic biodegradation of aromatic hydrocarbons: pathways and
prospects. Journal of Molecular Microbiology and Biotechnology, 15(2-3), 93-120.
Glucose and Cell culture (n.d). Retrieved September 21 2018. From
https://www.sigmaaldrich.com/life-science/cell-culture/learning-center/media-expert/
glucose.html
The Growth of Bacterial Populations (n.d). Retrieved September 21 2018. From
http://textbookofbacteriology.net/growth_3.html
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