my experiment I will be using investigating how different concentrations of
glucose affect the rate of fermentation of yeast. Yeast is actually a single
celled fungus that is found in the natural environment. Its scientific name is Saccharomyces Cerevisiae and is also
known by people as “the sugar fungi”. Yeast has been used for more than 5,000
years by early Egyptians who wrote hieroglyphics. Yeast was discovered after
the design of one of the most elaborate microscopes created in the 1800’s. This
microscope helped scientists like Louis Pasteur to find out that yeast is a
living organism. Over time, we learn that this yeast is used for alcohol
fermentation and also helps bread rise easier. There are 600 types of yeast
found throughout nature within fungus. According to “RedStarYeast” yeast is a
phase within fungus that is unicellular. Also, yeast requires a carbon and nitrogen
source, but this affects yeast because it cannot go through the process of
photosynthesis. Some of the most important carbon and nitrogen sources
that are used are urea, biotin, and amino acids. Also, an interesting
characteristic they have is that instead of using binary fission to divide they
use a technique called budding. As the bud is developed near the cell wall, it
detaches from the main cell into a smaller daughter cell. For each cell, the
budding process occurs about 15 times until it stops. The size of the yeast
cells can be compared closely to the size of a red blood cell in a human’s
body. Some main functions of yeast are to help fermentation occur, causes the
release of carbon dioxide and ethanol, and helps bread maturation. Fermentation
is also another important factor that is involved in my internal assessment.
Fermentation is a metabolic and chemical breakdown of a substance by bacteria,
yeast, and other organisms. Yeast is used in fermentation to take the sugar out
and produce oils, alcohol, and even different types of gases. Fermentation gets
its energy from anaerobic cellular respiration because oxygen is missing from
the process. Some factors that may affect fermentation is the concentration,
temperature, composition, etc. Another factor that will affect my IA is the
glucose I will be using. I will have 5 different concentrations for the amount
of glucose I will be using each time I do a trial and see how it affects the
rate of fermentation. Glucose is a simple sugar that is most commonly found in
the bloodstream. Glucose has the ability to breakdown monosaccharides and also
some disaccharides. According to
Livestrong.com “Glucose is the most common carbohydrate and nutrient in the
I chose to research for my internal
assessment “How does different amounts of glucose affect the rate of
fermentation of yeast?” I chose to research this question because it is an
interesting topic and also because it’s
a question that can help me understand and learn a new topic that can help further
my understanding of topics like fermentation and concentration levels. Also,
yeast has a scientific name which is Saccharomyces
Cerevisiae, this word translates to English as “sugar fungus”. The independent
variable of my experiment is the amount of glucose that will be used and my
dependent variable is the rate of respiration (breakdown of sugar to retain
energy). After coming up with my question and variables I will be using, I
created my own hypothesis about what will be the results from my experiment. My
hypothesis is the greater the concentration levels, the faster the rate of
respiration will be. The theory that influenced my decision about my hypothesis
is the theory that Louis Pasteur created stating that discussed how spontaneous
generation worked, but now this theory is not used anymore because the germ
theory that was created had new and better findings.
reliability, and sufficient of data collection:
The independent variable is the
amount of glucose I will be using in my experiment. I will be manipulating my
independent variable by changing the concentration levels of each, since I want
to find out if concentration affects the rate of fermentation. I will be using
5 different concentrations:0.5 grams, 1 gram, 1.5 grams, 2 grams, and also 2.5
grams of glucose. My range of the different concentrations was chosen because I
wanted the amounts to be very different from one another, so I chose 0.5 grams
as the smallest increment and 2.5 gram as the largest increment. The dependent
variable is the rate of respiration from the reaction. I will be using a CO2
probe to detect the product of fermentation. My controlled variables are the
amount of yeast(5 grams), amount of water(20mL), room temperature, time, and
probes. These controlled variables can impact the results by making the amount
of fermentation drastically different for each concentration. All of these
controlled variables will be held constant by using the measurements each time
for all the materials being used.
My plan to collect the data
addresses the research question because I will be taking note of my
observations for each trial I complete. My method for recording results include
doing a table for each trial that I’ll write all my measurements in. Then, in
the same table I’ll write my observations and record how much CO2 is released
from the fermentation. I will record all my data in the same form for each of
the trials I conduct. I will be using grams for measuring my yeast and glucose,
degrees Celsius to measure temperature of the water, milliliters to measure water,
and ppm for the pressure of the CO2 released. I will be using materials such as
timers, flasks, scales, co2 probe, and thermometers in my experiment to measure
out all my materials needed.
all materials needed.
the amounts of glucose on the scale to make sure you have the correct amount
needed (5 different amounts: 0.5g, 1g, 1.5g, 2g, 2.5g)
out 5 grams of yeast on the scale.
take a graduated cylinder and measure 20 ml of room temperature water.
you have all of these materials measured out, you will then mix all of them
together into an Erlenmeyer flask. Place the CO2 probe inside the flask and
begin measuring the rate of respiration every minute for 10 minutes.
your solution has fermented for 10 minutes take the probe out of the flask.
sure to record your data for each experiment.
steps 2-7 for each of the 5 concentrations of glucose. You will be doing 3
trials for each of the 5 concentration levels being tested.
Safety and Ethics:
There are no safety or ethical
concerns that have to be addressed for my internal assessment.