Summary of Mitosis
Friday, December 19, 2014
Thursday, December 18, 2014
Cell Communication
Introduction:
Yeast cells have two "sexes," called a-type and alpha-type. They locate each other via specific secreted factors. The exchange of factors causes them to mate. When these two cultures mix, the haploid cells (meaning they only have one complete set of chromosomes) become gamete cells (a mature sexual reproductive cell). The yeast cells halt asexual reproduction and grow into pear-shaped gametes called schmoos. When a-type and alpha-type come into contact with each other, they fuse, and the haploid nuclei form a diploid nucleus.
Conclusion:
This lab proves that yeast cells communicate through pheromones, also known as chemical signals transmitted between organisms. Because a-type and alpha-type cultures changed into their gamete form, they detected a signal from the opposite type. Also based on the fact that alpha-type yeast changed the most, we can conclude that this type releases the most mating factor.
Yeast cells have two "sexes," called a-type and alpha-type. They locate each other via specific secreted factors. The exchange of factors causes them to mate. When these two cultures mix, the haploid cells (meaning they only have one complete set of chromosomes) become gamete cells (a mature sexual reproductive cell). The yeast cells halt asexual reproduction and grow into pear-shaped gametes called schmoos. When a-type and alpha-type come into contact with each other, they fuse, and the haploid nuclei form a diploid nucleus.
Purpose: The purpose of the lab was to analyze the cell
signaling that occurs between the alpha-type and a- type yeast cells. The mating
interaction of the two yeast types mixed together was the focus of the
experiment. Our results for the mixed culture should support the idea of yeast
cells mating with the use of special factors that attach to the opposite mating
type. The characteristics of each yeast cell type were also individually
analyzed.
Methods:
1.We labeled 3 agar plates and 3 culture tubes as alpha-type, a-type, or mixed.
2. We added about 2 mL of sterile water to each tube and transferred a small amount of each yeast type into its designated tube.
To do this we used a toothpick to gather yeast cells and mixed the yest cells with the sterile solution by swishing the toothpick in the solution. For the mixed culture, we gathered a-type cells with a toothpick and placed it into the solution. Then with a different toothpick we gathered alpha-type cells and placed it in the same solution. Drops of yeast suspension were placed on their designated plates. We used different cotton swabs like in the picture below to spread the suspension on the agar plates.
To do this we used a toothpick to gather yeast cells and mixed the yest cells with the sterile solution by swishing the toothpick in the solution. For the mixed culture, we gathered a-type cells with a toothpick and placed it into the solution. Then with a different toothpick we gathered alpha-type cells and placed it in the same solution. Drops of yeast suspension were placed on their designated plates. We used different cotton swabs like in the picture below to spread the suspension on the agar plates.
We then looked at the yeast under the microscope at different intervals of time to see what occurred in the life cycle. We captured images at 0 minutes,30 minutes, and 24 hours later. Unfortunately, the 0 and 30 minute images are unable to upload, but below are images of the alpha-type, a-type, mixed-type, and experiment yeast suspensions on the agar plates after 24 hours.
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| Mixture of alpha and a type saw the most growth on the agar plate. Best cell communication |
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| alpha type yeast saw some growth too, but still not as dense as the mixed plate. Mating factors of the different yeast type can signal the opposite sex type, which impedes cell communication. |
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| a type yeast cells grew a bit |
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| we placed alpha and a type yeast on opposite ends of the plate (separated). Growth occured in the sides of each individual type but failed to develop towards the middle of the plate since the mating factors never or barely came in contact. Data/graph  |
Discussion
A large part of analyzing this lab is noticing the differences in the yeast over a period of time. In order from least amount of change to most amount of change overnight it goes; the mixed separate dish, a-type, mixed, and then alpha-type. The reasons that the separate mixed was the least had to do with the fact that we started the yeast on opposite sides of each other. This makes it difficult for the yeast cells to sense the actual amount of cells in the dish, and therefore they do not shmoo as much as they should. Even when they do, it is a far distance across the dish for these little cells to get to. This slows down the overall process even more. The reasoning for the mixed being one of the highest producing ones is because it was mixed. This gives more opportunity for diversity within the cells and makes them able to produce faster. The reasons, I believe, that alpha was the largest change, was just due to its genetic make-up. It was obviously more adapted to move and produce quickly. This experiment proves how cells communicate with one another. After they got to a certain density, they stopped producing. We were also able to see how they changed their cytoskeleton to reach one another. This experiment truly shows how cells signal one another.
This lab proves that yeast cells communicate through pheromones, also known as chemical signals transmitted between organisms. Because a-type and alpha-type cultures changed into their gamete form, they detected a signal from the opposite type. Also based on the fact that alpha-type yeast changed the most, we can conclude that this type releases the most mating factor.
Thursday, December 11, 2014
Plant Pigments and Photosynthesis
Plant Pigment Chromatography
Purpose: In this experiment, we were trying to separate and identify pigments as well as other molecules found in plant extracts. We needed to calculate the Rf constant, which represents the relationship between the distance moved by a pigment to the distance moved by the solvent. This helped us determine the factors involved in the separation of pigments.
Methods:
We got a 50mL graduated cylinder that had 1 cm of solvent in the bottom. Then we cut a piece of filter paper long enough to reach the solvent and made sure the end was cut into a point.
We used a coin to crush leaf cells about 1.5 cm above the point of the paper. By rubbing the coin against the leaf, we were able to extract pigments.
We put the filter paper in the cylinder so the pointed end was barely immersed in the solvent, and stopped the cylinder.
When the solvent moved about 1cm from the top of the paper, we removed the paper and marked the location of the solvent and the bottom of each pigment band. Next we measured the distance each pigment moved from the bottom of the pigment origin to the bottom of each band.
Conclusion: The 5 different pigment bands seen on the paper demonstrate that a mixture of these pigments is needed for photosynthesis to occur. The light spectrum of each pigment provides the spinach leaves with a large source of light that can be used to power the light reactions of photosynthesis. The first line of pigment from the bottom appears to be chlorophyll b since it is the most polar and most soluble due to its carbonyl group. This high polarity inhibits this pigments ability to move up the paper. Chlorophyll a is the next most polar which makes it the 2nd pigment line. The less polar pigments are able to travel up the paper since they are less likely to create interactions with the paper. Errors that could’ve have occurred might be calculation errors and measurements.
Sources:
Photosynthesis:
Purpose: We were trying to test the hypothesis that light and chloroplasts are required for light reactions to occur. To do this we had to measure the transmittance and absorbance from four cuvettes, each of with contained a different mixture. By measuring transmittance/absorbance, we were able to determine photosynthetic rates. We also took data at different times to see how light intensity affects the rate of photosynthesis.
Methods:
We set up an incubation area that included a light and a water flask.
Then we prepared each cuvette. The first one included 1mL phosphate buffer, 4 mL H2O, and three drops of unboiled chloroplasts. This served as our blank, and we used it to calibrate the colorimeter (we measured the light transmittance through each of the other tubes as a percentage of light transmitted through this tube).
The other cuvettes all had the phosphate buffer, H2O an DPIP in them. Cuvette 2 was covered in foil and had 3 drops of unboiled chloroplasts in it. 3 had three drops of unboiled chloroplasts. 4 had 3 drops of boiled chloroplasts. 5 had no chloroplasts whatsoever.
After mixing cuvette 2, we removed the foil sleeve and put it into the colorimeter. Then we recorded % transmittance and absorbance at time 0. We replaced cuvette 2 in the sleeve and placed it in the incubation area. We took and recorded additional data at 5, 10, and 15 minutes. With each cuvette, we did the same steps, only no foil sleeves were involved.
Data and Graphs
Discussion:
Purpose: In this experiment, we were trying to separate and identify pigments as well as other molecules found in plant extracts. We needed to calculate the Rf constant, which represents the relationship between the distance moved by a pigment to the distance moved by the solvent. This helped us determine the factors involved in the separation of pigments.
Introduction:
Paper chromatography separates the components of cell
extract. Different molecules and pigments move up the paper at varied rates due
to differences in solubility, molecular mass, and hydrogen bonds (1).
Chlorophyll a, the primary pigment that absorbs light, absorbs mostly violet
and blue light for photosynthesis. Chlorophyll b is an accessory pigment that
broadens the absorption spectrum on the spinach leaf by absorbing different
wavelengths than chlorophyll a. Chlorophylls contain oxygen and nitrogen and
have a greater affinity for the paper (3). Carotenoids are also accessory
pigments that absorb violet and blue-green light. Their function is to perform
photoprotection to dissipate excessive light energy that could damage
chlorophyll pigments. They are very soluble and form no hydrogen bonds with the
paper. Xanthophyll is a division of the carotenoid group that has a similar
structure to carotenes but contain oxygen atoms and create hydrogen bonds with
the paper. (2).
We got a 50mL graduated cylinder that had 1 cm of solvent in the bottom. Then we cut a piece of filter paper long enough to reach the solvent and made sure the end was cut into a point.
We used a coin to crush leaf cells about 1.5 cm above the point of the paper. By rubbing the coin against the leaf, we were able to extract pigments.
We put the filter paper in the cylinder so the pointed end was barely immersed in the solvent, and stopped the cylinder.
When the solvent moved about 1cm from the top of the paper, we removed the paper and marked the location of the solvent and the bottom of each pigment band. Next we measured the distance each pigment moved from the bottom of the pigment origin to the bottom of each band.
Data and Graphs
Discussion:
In this lab we found out that the solubility, size of
particles, and their attractiveness to the paper are all involved in the
separation of pigments. The different solubility’s
of the pigments would change the Rf values. The reaction center contains
chlorophyll a. The other pigments collect different light waves and transfer
the energy to chlorophyll a. Xanthophylls
went furthest up the paper. We examined that the closer the rf factor to each other
the distance of the pigment traveled is closer
to the distance traveled by the solvent. The separation of pigment in chromatography
allowed us to look at the different pigments there in the plant. We can tell if
a plant will reflect the color that showed and doesn’t absorb as much from the
light and wavelengths. The orange, yellow, and green light will be somehow reflected
from the Spinach leaves. To find the RF you take the distance pigment migrated divided by the distance solvent. The RF for band 1 is .252 mm and RF band 2 is .326. Band 3 is .467 and RF band is .585. The larger the RF is, then the more distance that was traveled by the pigment. Pigments like the carotene have the highest RF factor since they are the least polar and travelled the most. The chlorophyll pigments are extremely polar and have a high affinity for the paper which slows them down.
Conclusion: The 5 different pigment bands seen on the paper demonstrate that a mixture of these pigments is needed for photosynthesis to occur. The light spectrum of each pigment provides the spinach leaves with a large source of light that can be used to power the light reactions of photosynthesis. The first line of pigment from the bottom appears to be chlorophyll b since it is the most polar and most soluble due to its carbonyl group. This high polarity inhibits this pigments ability to move up the paper. Chlorophyll a is the next most polar which makes it the 2nd pigment line. The less polar pigments are able to travel up the paper since they are less likely to create interactions with the paper. Errors that could’ve have occurred might be calculation errors and measurements.
Sources:
3. Lab
Introduction
Photosynthesis:
Purpose: We were trying to test the hypothesis that light and chloroplasts are required for light reactions to occur. To do this we had to measure the transmittance and absorbance from four cuvettes, each of with contained a different mixture. By measuring transmittance/absorbance, we were able to determine photosynthetic rates. We also took data at different times to see how light intensity affects the rate of photosynthesis.
Introduction:
Plants depend on light energy to fuel the light reactions of
photosynthesis, which produces the reactants of the light independent
reactions. The absorption of light occurs in a photosystem light-harvesting
complexes which contain various pigments (discussed in lab 4A) that harvest
light and send it to the reaction-center complex. Electrons are boosted to high
energy levels and must be carried by the electron transport chain and another
photosystem in order to return to a more stable condition (1). In this process,
ATP and NADPH are produced. NADPH is produced by the reduction of NADP+. DPIP replaces the electron acceptor NADP+ in
dye-reduction. DPIP begins with a blue liquid and as it’s reduces it becomes
colorless.
Methods:
We set up an incubation area that included a light and a water flask.
Then we prepared each cuvette. The first one included 1mL phosphate buffer, 4 mL H2O, and three drops of unboiled chloroplasts. This served as our blank, and we used it to calibrate the colorimeter (we measured the light transmittance through each of the other tubes as a percentage of light transmitted through this tube).
The other cuvettes all had the phosphate buffer, H2O an DPIP in them. Cuvette 2 was covered in foil and had 3 drops of unboiled chloroplasts in it. 3 had three drops of unboiled chloroplasts. 4 had 3 drops of boiled chloroplasts. 5 had no chloroplasts whatsoever.
After mixing cuvette 2, we removed the foil sleeve and put it into the colorimeter. Then we recorded % transmittance and absorbance at time 0. We replaced cuvette 2 in the sleeve and placed it in the incubation area. We took and recorded additional data at 5, 10, and 15 minutes. With each cuvette, we did the same steps, only no foil sleeves were involved.
Data and Graphs
Discussion:
The graph shown above proves that there is an inverse relationship between transmittance and absorbable. As the amount of blue dye solution decreased, transmittance increased.
Each curvette had a specific purpose:
Cuvette 1 with no DPIP and chloroplasts was used to calibrate the colorimeter. The difference between unboiled and boiled chloroplasts is that boiling chloroplasts denatures them which changes the shape of their protein and might lead to changes in function. Boiling chloroplast reduces the efficiency of these chloroplasts which negatively impacts the rate of photosynthesis.
Cuvette 2 with unboiled chloroplast,DPIP, and no light (due to the aluminum foil wrapped around) supported the idea that light is needed for the rate of photosynthesis to increase. Cuvette 3 with unboiled chloroplasts, light, and DPIP demonstrates that perfect conditions can result in a quick rate of photosynthesis. The chloroplasts are functioning properly, light fuels the light reactions that produce products used in the dark reactions, and DPIP acts as a new electron carrier. Cuvette 4 had all the same elements of Cuvette 3 except that Cuvette 4 had denatured chloroplasts, which negatively impacted the rate of photsynthesis. Finally, Cuvette 5 was used to demonstrate that DPIP can't be reduced on its own. Chloroplasts are needed to reduce DPIP, even if light is present DPIP can't function without the light that excites electrons.
In this lab the DPIP is the electron acceptor in this
experiment. The molecule that found in chloroplasts is DPIP and substitutes for
the NADP molecules. The source of the electron that will reduce DPIP is the electrons
that come from the photolysis water. The
amount of light transmittance is measured by a spectrophotometer. The effect of
darkness will have no reaction take place. The effect of boiling the chloroplast
on the subsequent reduction of DPIP will stop the reduction. The difference in the percentage of
transmittance between the live chloroplasts that were included in the light and
those that were kept in the dark was the light energy. In the dark there isn’t a
flow of electrons and photolysis water while the light does. In Cuvette one was
our control and set to 100% transmittance. Cuvette two was light reaction work in
dark. In cuvette three was light reaction
work in live chloroplast. Cuvette four boiled chloroplast. Finally, in cuvette five shows us that chloroplast
is needed in plants.
Conclusion:
The spectrophotometer measured the light transmittance
through the cuvettes and chloroplast solutions. The biggest change in transmittance
(low to high) occurred in the cuvette with unboiled chloroplasts that was
placed in the light. This proves that the rate of photosynthesis increased the
most. Factors like light availability and denaturing of chloroplasts affected
the rate of photosynthesis. Errors could have occurred from simple mistakes in
calculations. The amount of time that the cuvettes spent in front of the light
might not also be exact which could lead to skewed data.
Sources
1. Biology Book
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