Friday, December 20, 2013

Cell Communication Lab: Yeast Cells

For this lab, we focused on cellular communication. Cell communication happens between unicellular organisms and inside multicellular organisms. To communicate with their neighbors, cells secrete chemicals to other cells to "switch on" the cell. Organisms communicate via chemical signals to coordinate functions and to respond to the stimuli in their environment. A molecular signal reaches it receptor on the cell, and a series of reactions occur. Cells can communicate by direct contact, local signaling, or long-distance signaling. Yeast cells are unicellular fungi, that can reproduce sexually or asexually. Yeast can be cultured on solid or liquid media. If cells are streaked over a solid medium, they grow in colonies on top of one another while yeast cells that are mixed into a liquid medium grow evenly throughout it. During this experiment we observed yeast cells and their responses in both solid and liquid mediums.

The purpose of this lab was to determine how cells, like yeast cells, communicate with one another. Yeast cells do not have legs and cannot swim to other cells to mate with them, so we wanted to see exactly how that would happen. We were also testing to see how much the yeast cells would reproduce during the time increments we set for them. We counted the different types of cells after 0 minutes, 24 hours, 24 hours and 30 minutes, and 48 hours. The independent variable is the amount of time that the cells had to reproduce. The dependent variable is the percent of the total of the cell that a certain type of cell was, like a single haploid cell. 

First, we labeled each agar plate and corresponding culture tubes "a-type," "alpha-type," and "mixed type". We added about 2ml of water using a pipet to each culture, then used a toothpick swab to pick up a colony from each plate (using a different pick each time). Following this, our lab group observed each yeast Petri dish under the microscope: once at the start, after 24 hours, 24 hours and 30 minutes, and again after 48. We counted to the best of our abilities the cells we observed under the microscope. 
During this lab we were instructed to practice the "sterile technique," meaning handling tools without contamination. By doing so, we did not allow our tools of this lab to touch anywhere that's not a "clean zone". We never used a pipet, swab, or spreader more than one time. If we did, who knows what kind of bacterial growth we would see. We were sure not to let our skin touch the yeast either. 


          Alpha culture after 24 hours 

                         Mixed culture after 48 hours 
            Alpha type after zero minutes 

In this experiment we wanted to test the communication in different strands of yeast. We tested  A type, Alpha type, and mixed type. The  key difference between these types are the different genes in Alpha and A type.. These A and alpha type can combine to make a mixed cell via single transduction pathway. The mixed cells are a combination of A type and Alpha type, these cells can become a haploid, budding haploid, zygote, budding zygote, or a shmoo. A haploid is a single cell. A budding haploid is a single cell with a growth on the side. A zygote is two cells that look like an infinity sign. The budding zygote is 2 cells that are like infinity signs with a growth that looks like a dot. A schmoo looks like a pear, and it the two cells combining together. The mixed type can have shmoos, both haploids, and both zygotes. The A factor and alpha type only have budding haploids and haploids, this is because the A type and Alpha type had nothing to mate with. Single transduction pathways use several steps to produce a cellular response.  The yeast cells use G- protein receptors system to mate. G protein receptors are also single transduction pathway. G proteins consist of a signaling molecule, a g protein, G protein coupled receptors and an enzyme.  The signaling comes to bind to the G protein on the extracellular side. This causes the G protein coupled receptor to change shape on the cytoplasmic side. When the receptor changes shapes a G protein to bind to it. This activates G protein to make a GTP and get ride of the GDP the protein currently was holding. Then the active G protein combines with the enzyme to active the enzyme, to trigger a cellular response. Once the enzyme is activated, the G protein acts like a GTPase enzyme. GTPase use hydrolysis to get ride of the third phosphate. To make the protein inactive and ready for reuse. This yeast cells are able to do this by commicating with secret messages. These secret messages are called pherenomes. In the graphs you can see that the for the first 30 minutes on the A type of Alpha type the number were very high at first but as time progressed to 24 hours the number of haploid and budding haploid started to decreases. This happened because the cells had no one to mate to so they started to die off as time went on.  For the mixed type the numbers increased as time went on. This is because the Alpha and A type were able to mate, and create more yeast cells. 

This experiment can be fixed by wearing gloves. Maybe if we wore gloves it could decrease on contamination. The lab was very sterile but if we had gloves we could make it even more  sterile. This could help prevent other types of bacteria from growing. Also, our lab group was not very accurate when we were counting the different types of cells. The next time we do this lab, we would work on counting them more accurately to get better data. 

Cell communication is required in many different biological functions (sexual reproduction included). In this lab, we observed cells signaling each other in two strains of the yeast Saccharimyces cerevisiae. In the A and Alpha type cultures, we examined the life cycle and mating routines in the yeast and in the mixed cultures, tons of bacteria were living throughout. 

Friday, December 6, 2013

Photosynthesis and Chromatography Lab


     Photosynthesis is a process that converts light energy into chemical energy that can be used to fuel the organisms. Below is the formula for photosynthesis.
                                       6H20 + 6CO2   -->  C6H12O6 + 6O2
         Photosynthesis has two parts, the light dependent reactions (light reactions) and the light independent reactions (dark reactions). The light reaction happens in the thylakoid and convert light energy into chemical energy. This chemical reaction must take place in the light. The dark reaction takes place in the stroma within the chloroplast, and converts CO2 to sugar. Although called dark reactions this reaction needs the energy  produced in the light reactions in order to trigger the reaction. Organisms that carry out photosynthesis and make their own organic molecules are called autotrophs.
         Chloroplasts are organelles in plants that conduct photosynthesis.  Chloroplasts capture light energy from the sun to produce the energy stored in ATP and NADPH photosynthesis.  Under certain circumstances the proteins in chloroplasts can be denatured or unable to conduct photosynthesis, such as high temperature or lack of light.  In this experiment we will test these circumstances and see for ourselves the affects that can harm photosynthesis.
         This experiment tests the light reactions. The light reactions are the first step of photosynthesis. The light reaction have 2 photosystems. There is photosystem I and II, they can be abbreviated PS I and PS II . PS II comes before PS I. PS II is also called P680, because it absorbed a wavelength of 680 nm the best. PS I is also called  P700, because it absorbs a wavelength of 700 nam the best.In PS II light enters it and stimulates the electrons. Water also enters it and excites the electrons by splitting water, H+ remains in PS II and O2 leaves the photosystem. The electrons bounce around till they reach the chlorophyll a molecule. The electrons are then sent to the primary electron acceptor and makes them 680+. 
          After the electrons are sent to an electron transport chain. Electron transport chains help lower the energy in electrons. It also helps drive chemiosmosis  to make ATP.  Some of the electrons that are in the transport chain get sent to the chlorophyll a molecules of PS I. PS I electrons come from light and the electrons from PS II. PS I  is similar to PS II, in having the chlorophyll a molecules pushing electrons to the primary electrons acceptor. The difference is in the end. Instead of going to an electron transport chain to make ATP,  P700+ goes through the electron transport chain to be reduced by the enzyme, NADP+ reeducase to make NADPH. Both of these process are meant to make ATP and NADPH for the Calvin cycle. 
The purpose of this experiment was to test how enzymes (in this experiment the enzyme was DPIP) would effect how much is transmitted. We wanted to see what would happen if we used boiled and unboiled chloroplast. We would see if the boiled maybe decreased the prcent transmitted.  Also we wanted to see the effect of having the curettes being placed in the light and dark. We could test if curettes kept in the dark would lower the percent transmitted.  In this experiment the independent variable was the DPIP and the dependent was the precent transmitted.
       First we set up the 5 different test tubes. The first test tube was a blank. It had 1 mL of phosphate buffer, 4 mL of distilled H2O, no DPIP, and 3 drops of unboiled chloroplast. The second test tube 1 mL of phosphate buffer, 3 mL distilled H2O, 1 mL of DPIP, and 3 drops of unboiled chloroplast. The third test tube had 1 mL of phosphate buffer, 3 mL of of distilled H2O, 1 mL of DPIP, and 3 drops of unboiled chloroplast. The fourth test tube had 1 mL of phosphate buffer, 1 mL of DPIP, and 3 drops of boiled chloroplast.  The fifth test tube was 1 mL of phosphate buffer, 3 mL of distilled H2O, 1 mL of DPIP, and no chloroplast. When the test tube was ready to be measured in the spectrophotometer the contents in the test tube would be put in to a cuvette. For each test tube the chloroplast was not added until it was put into a cuvette. After we got all the test tubes ready, we filled up a big beaker of water and behind the beaker of water was a huge floodlight. The first test tube was a blank that was used to calibrate the spectrophotometer. After it was used to calibrate it was kept in the light. Because we ran out of time we measured all the test tubes at the same time. We would put test tube 2 in the spectrophotometer then get it's reading. Then we would take the test tube out and put it in the light for 5 minutes. But the 2nd test tube is covered in foil to prevent the light from getting in. Right after that we would put in test tube 3, get a reading on the spectrophotometer and then put it in the light for 5 minutes. This same thing happened to test tube 4 and 5. After every 5 minutes we would take the test tube out of the light and measured in in the spectrophotometer we would go up to 15 minutes. We would take measure if the test tubes in the order of 2,3,4,5.
We repeated this experiment again. This time the experiment was slightly changed. The content that was put in each test tube was the same except that for every 1 drop of chloroplast we would add 3 drops of water  to try to dilute the chloroplast. This took place in test tubes 1-4. It did not happen in test tube 5 because it had no chloroplast in it. Everything else in the experiment was the same like the process of measuring with the spectrophotometer. 

                                                    Zero minute mark 

                                                      Five minute Mark 

                                                Ten minute Mark 
                                                    Fifteen minute mark 
                   Test tubes with Solutions 
             Cuvettes Sitting in the Light 

Our group had to perform the experiment twice because of inaccurate data. The first time we ran the experiment, the percent transmittance jumped well past 100% for several cuvettes at the 0 minute mark, which is clearly inaccurate. After having the chloroplast added to the rest of the solution for less than a minute, there shouldn't be that strong of the ratio of intensity of the light that has passed through the sample to the intensity of the light when it entered the sample. This led us to believe that our data was not correct. We believe that the solutions were using up the chloroplast too fast, causing the unreliable data. However, after performing the experiment a second time, we received more accurate data, especially since we deluded the chloroplast with one drop of water per one drop of chloroplast. In cuvette one there was no DPIP added. The data stayed at zero the whole time. Photosynthesis was not able to take place then because there was nothing to act as an electron acceptor, similar to how DPIP would have done. In cuvette two, unboiled chloroplast was added and the cuvette was wrapped in tinfoil, leaving it in the dark. Photosynthesis was not able to occur because the light reactions of photosynthesis need light to take place, but since the cuvette was wrapped in tinfoil, there was no light to provide light energy for the reaction. No electrons were made, and the color didn't change. The transmittance at each 5 minute mark stayed within a three percent range of one another for this particular cuvette for these reasons. In cuvette three, unboiled chloroplast was added, and it was placed in front of the light. The cuvette was placed in front of the light so this provided light energy for the light reaction to take place. This is why the transmittance of this cuvette went up by a total of about 9% throughout the experiment, the most by far of any cuvette in the experiment. In cuvette four, boiled chloroplast was added, and the cuvette had been placed in front of the light. It was hard for photosynthesis to occur in this cuvette because since the chloroplast was boiled, this denatures it. Photosynthesis is not able to take place with unliving chloroplast. This is why the percent transmittance for this cuvette went down. No reaction was able to take place at all. In cuvette five, there was no chloroplast added and the cuvette was not placed in front of the light, however, it was not wrapped in tin foil in the dark either. The percent transmittance stayed the same for this cuvette since there was an absence of chloroplast and light to get photosynthesis going. 
           Since we ran the experiment twice there were two conclusions. As shown in the methods and discussion, The first time we ran the experiment the percent transmittance was over 100 for the cuvettes, which was not what was supposed to occur. We came to the conclusion that we needed to delude the solution in order for the usage of chloroplasts to slow down. In the second experiment we changed the procedure by adding an extra drop of water with every drop of chloroplast. After this slight change the data showed that the percent transmittance was no longer sky rocketing but a gradual increase. The adding of water to delude the chloroplast definitely made an impact on our results and made significantly more accurate. Yay go chloroplasts!


Paper chromatography is used to separate and identify pigments and other molecules in a solution that contain many complex molecules. The paper creates stronger and weaker bonds with certain solutes (molecules). How strong the bond is depends on the solubility of the solute in the solvent. The further a pigment (or molecule) travels up the paper, the more soluble that solute is in the specified solvent and forms weaker hydrogen bonds with the paper itself. 
Carotene forms no hydrogen bonds with cellulose; therefore, it is very soluble in the solvent. Xanthophyll forms hydrogen bonds with cellulose which slows down its progress up the the chromatography paper because it is less soluble.  Chlorophyll contains oxygen and nitrogen which causes it to form stronger bonds with the paper and move up more slowly.
The distance the pigment moved divided by the distance the solvent moved is called the Rf constant. It illustrates the relationship between the two factors.

This lab tries to show how many different pigments are present in a plant through paper chromatography. This allows all the pigments to separate due to their solubility and bonding.  When we calculate the Rf constant we can more easily compare which pigments are more soluble and form certain type of bonds because the distance the solvent moved is already calculated in as a comparison. 

Many materials were used in this experiment, such as filter paper, solvent, cylinder, a coin, and a spinach leaf. As instructed, we cut a 1.5 cm point on the tip of the filter paper and crushed a spinach leaf with a penny in order to extract pigments of the leaf cells. By doing so, a green line of spinach particles appeared near the end of the paper. We then placed the paper into a graduated cylinder, and let it sit until the pigments traveled almost to the top. We removed the filter paper right away and marked the furthest migration with a pencil, then all the others. The Rf was thus calculated from the distance of the pigment of which it traveled.


       Measurement of Migration of Pigments 

      Measuring the Migration of Pigments 

        Spinach Leaf Pigments in Solvent 

In the lab we found that xanthophyll moved the furthest up the paper. Also, it had an Rf constant of one. This shows that this pigment was the most soluble and most polar because it was able to easily travel up the paper with the water.  Carotene was next. It had an Rf factor of .547. Then, chlorophyll A with an Rf of .444. Finally, chlorophyll B with an Rf of .282. We can observe that the closer the Rf factor is to one the more soluble and polar it is because the distance the pigment traveled is closet to that of the distance traveled by the solvent. The separation of pigments in chromatography allows us to examine the different colored pigments present in plants. We can from this predict which light and wavelengths of light will be most absorbed by this plant because the plant will reflect the colors present in the leaf and not absorb as much of them, This means that green, yellow, and orange light will be reflected in some way or form in the spinach leaf. The other from least absorbance to greater absorbance is in the respective order.

         By performing this lab and analyzing its results, our lab group found that the many pigments found in chloroplast take part in the process of absorption of energy from the sun. The filter paper and its color spectrum showed each pigment's solubility from which we measured each pigment's migration


Monday, November 18, 2013

Cellular Respiration Lab

Purpose- The purpose of this experiment is to determine whether germinated or non-germinated seeds had a higher respiration.  We did this by determining the rate of respiration for the non-germinated seeds and then with the germinated seeds before and after having sat in cold water. We used temperature as variable to see if the results would differ.  We also tested glass beads to determine a control between the two.  This lab helped us to understand the process of respiration and what can potentially slow down this process.

Introduction- Cellular respiration is a multi- step metabolic process that produces energy by the oxidation of organic molecules. Humans and animals go though this process. This process is aerobic and anaerobic. Aerobic means it has oxygen and anaerobic means without oxygen. The reason it is anaerobic and aerobic is because one step is anaerobic and the other steps are aerobic.  The process starts with an organic molecule and oxygen and ends with carbon dioxide, water, and energy. An example of this is glucose going through cellular respiration C6H12O2 + 6O2 -> 6 CO2 + 6 H2O + Energy. This is also called a redox reaction. Redox reactions are the transferring of electrons. The name redox comes from a mixture of the 2 things happening in a redox reaction.  One substance in being reduced (gains electrons) and oxidation (losing an electron). The electrons are transferred with coenzymes. NAD+ is the oxidized state and NADH is the reduced state.  Cellular respiration  goes through 3 steps. The first step is glycolysis which is an anaerobic process. Glycolysis end products are 2 ATP and 2 NADH and 2 pyruvate. The 2 pyruvate are oxidized to become 2 acetyl CoA . The next step is called the Krebs or Citric Acid cycle. The Krebs cycle is named after the scientist who discovered it Hans Krebs. This cycle uses the 2 acetyl CoA. This means that this cycle is repeated. After the 2 times the end products are 6 NADH and 2 FAD2.The last step is oxidation phosphorylation it consists of the electron transport chain and chemiosmosis. The electron transport chamber helps gradually decreases the free energy. During this time H+ are being pumped across the membrane and it creates a H+ gradient. In chemiosmosis the flow of H+ helps power  ATP synthesis.Oxidation phosphorylation   creates 26- 28 ATP. After all the steps are complete  it should result in about 30-32 ATPs. In this experiment we will use these concepts to help us understand the CO2 release.

                                                        Glass beads 

                                                 Germinating barley seeds 
                                           Non germinating barley seeds 
                                               Cold germinating barley seeds 
             Germinating barley seeds 
                      Barley seeds

   CO2 chamber- calculated amount of CO2 being produced by seeds and glass beads. 

Methods- We picked out 25 glass beads and 25 barley seeds that were germinated and 25 seeds that were not germinated. The 25 glass beads were used for a control group. We then put 25 glass beads in the respiration chamber. We let the beads the glass beads sit for 10 minutes. After the ten minutes was up we started to take measurements of CO2, with a device that measures CO2 contents.  We recorded the data on our Vernier Lab quest . Next we performed the same steps from the glass beads to the germinating Barley seeds, non germinating barley seeds. Except the  germinating barley seeds that have been placed in a cold ice bath for ten minutes. 

Discussion- Germination causes a higher rate of respiration than the non-germinating peas. This is because a seed needs to have optimal conditions in order for it to germinate. These conditions are met through cellular respiration which provide the correct amount of energy for these reactions to occur. Non-germinating seeds are "dormant" and their energy is stored (this is why nuts and seeds have so many calories); therefore, they don't need as much energy to perform vital processes. The beads served as a control group because no cell respiration occurred. This allowed for certain factors such as pressure to be accounted for without having to directly control it.

Lower temperature slows down the respiration process. The rate at which a reaction occurs, increases with higher temperatures. The higher the temperature of a solution, the faster the molecules are moving in solution. There are more collisions between reacting molecules, and more of those collisions have the necessary kinetic energy required to break bonds and perform necessary function. Respiration is a chemical reaction that breaks down glucose into carbon dioxide and water, so it works in the same way. The higher the temperature, the more kinetic energy because of the molecules moving around, the more cellular respiration can occur.

Not maintaining a constant temperature in the water bath could have caused inaccurate results. Keeping the cold, germinating seeds at a constant temperature would've made the experiment more accurate. Putting the respiration chamber in an ice bath would be a good idea. 

Conclusion- We concluded from the lab that germinating peas that have been at room temperature or in a cold ice bath have a higher rate of cellular respiration. This is because when plants germinate, they are coming out of the seeds as sprouts and beginning to grow, thus needing to use up more oxygen. Seeds that are not germinating do not need as much oxygen because they are not beginning to grow. The germinating seeds that were placed in the cold ice bath had a slightly slower rate of cellular respiration than the germinating seeds at room temperature because the cold temperature slowed it down. The rate of respiration is faster in warmer temperatures. 

References- References-

Monday, November 4, 2013

Enzyme Catalyst Lab


2B) The purpose of this part of the lab was to determine the amount of hydrogen peroxide (H2O2) initially present in a 1.5% solution. We were testing the concept of establishing a baseline without adding catalase (enzyme) to the reaction mixture. The dependent variable is the hydrogen peroxide (H2O2), water, and H2SO4. The independent variable is the amount of KMnO4 used in the burette to get the solution a persistent pink or brown color. 

2C) The purpose of this part of the lab was to determine the course of an enzymatic reaction in a reaction. In order to do this, we needed to measure the amount of substrate disappearing over time increments of 10, 30, 60, 90, 120, 180, and 360 seconds. We were testing the concept of the amount of substrate decomposed in these time amounts. The dependent variable was the amount of hydrogen peroxide, yeast, and water that were combined in the beaker while the independent variable was the amount of time the reaction was allowed to take place before the KMnO4 was added to stop the reaction. 

        This lab deals with enzymes, catalyze, and the reaction of the two together. Enzymes are proteins produced by living cells, and a catalyst is a substance that speeds up the reaction and lowers reaction energy.  Enzyme catalyst connects to a site of an enzyme, lowering the amount of energy required to produce a reaction with the substrate.
In this experiment we used the titration method to determine the quantity of substances in many different types of solutions.This experiment will help us to observe how catalyst enzymes work to speed up the reactions and turn hydrogen peroxide into water and oxygen gas.  By letting these reactions take place for different amounts of time, we could compare and contrast which conditions and time limits cause more of a reaction and which cause less. WE LOVE ENZYMES!!!!  :)


2B) We tested a baseline as a comparison for the experiment. We mixed water, hydrogen peroxide, and sulfuric acid. After removing a 5 mL sample of the mixture and added KMNO4 until the pink color remained visible in the liquid.

2C) We had 7 different cups labeled with 7 different times (10, 30, 60, 90, 120, 180, 360 seconds).  In each cup we put the same amount of hydrogen peroxide, yeast, and acid; however, after adding the hydrogen peroxide and yeast, we controlled the amount of time we let the reaction take place. In order to stop the reaction we added sulfuric acid after a specific number of seconds. The times listed on the cups represented the amount of time we let the yeast and hydrogen peroxide react. Then, we removed a 5 mL sample and added KMNO4 until the pink color remained visible in the liquid. The longer we let the reaction take place, the less KMNO4 was needed in order to make the color stay.
Data from part 2C

Data used from part 2C
Graph 2.1

2B) In this experiment the level of KMnO4 the burette dropped from 27 ml to 24 ml. This means that the level of KMnO4 dropped 3.1 ml.  These results are important because the baseline is used in every experiment. The baseline is used too test the amount of H2O2 in a 1.5 solutions.

2C) In this experiment we want to test the rate of spontaneous conversion of H2O2 without an enzyme. We had to use the baseline again but this time the baseline difference between the initial and final reading is 3.7 instead of 3.1. It is different because we had to make a new baseline. The baseline is not supposed to sit for 24 hours. We have to account for the natural breakdown of H2O2. It can naturally breakdown but also external factors can make it breakdown more like enzyme and temperature change in the room. Without a enzyme only .6  ml has been decomposed. Using the formula (ml baseline - ml 24 hour / ml  baseline) X 100 we found out that 19.3 % has been decomposed. It makes sense that the number is low because there was no enzymes in the  experiment. The enzymes can help lower the activation energy.  Activation energy is how much energy it takes to start a reaction. H2O2 could have a high activation energy and that could be a reason why not a lot of H2O2 decomposed. I think the way that the experiment was set up it was good. It was beneficial that we all used the same 24 hour solution. It helps us standardize our results. If even all made our own 24 hour solution all of our results could be greatly varied, like we could mess up on the make up of the solution or how much time it spends sitting.

2D) In this experiment we tested the same reaction as the last experiment but instead of no enzyme we added enzymes to the experiment. In this experiment we see that as time progressive  the enzymatic rate lowered. The highest rate is the first in the first time interval (0-10) . It was the highest because iit had the highest catalysis amount and the most amount of H2O2 to decompose. The lowest rate was the last time interval  (180 -360) there are 2 possible reason why it is the lowest. One is the H+ content makes the solution more basic. This moves the solution away from its optimal ph, thus causing the enzyme to denature. Denaturing is when the enzyme becomes biologically inactive because the proteins begins to unfold. Another reason could be is that all the catalysis amount is at the lowest because all the enzymes are already being used.  This causes an inhibiting effect on reaction. Inhibiting is when the reaction is stopped or slowed down. If we were to lower the temperature it would still cause the enzyme to denature. Like ph, enzymes also have an optimal temperature if the temperature gets too low or too high it will denature. 


By performing this experiment we were able to determine the quantity of a substance in different solutions through the titration method. We also recorded the rate of how quickly the catalsye enzyme was able to convert Hydrogen Peroxide to water and oxygen gas, which helped us expand our knowledge of the importacne enzymes and how they function.


Titrating solutions

Yeast- catalyst used to start the reaction
Color of solution after being titrated 

All the solutions being set up to be timed with the catalyst 

Monday, October 21, 2013

Diffusion Osmosis Lab

1A) This part of the lab tested permeability. The lab used a glucose/starch solution inside a dialysis bag submerged in an iodine solution (independent variables) to determine whether the dialysis bag was selectively permeable. This was determined by the color of the solutions in the bag and inside the beaker (dependent variables) after 30 minutes of the bag being soaked in the IKI.

1B) In this part of the lab we tested the net movement of water through a selectively permeable surfaces that contained hypertonic and hypotonic solutions by osmosis. The lab used dialysis bags filled with solutions of different molarities (independent variable) submerged in distilled water to figure out how much osmosis would occur with the hypertonic versus the hypotonic solutions. This was determined by the mass of the bag (dependent variable) after being submerged in the water for 30 minutes.

1C) The main concept tested in this part of the lab was water potential. Potato cores were submerged in solutions with different molarities (independent variable) in order to determine the water potential of a potato cell. The mass
of the potato cores (dependent variable) after they were soaked in the solutions overnight revealed the water potential of the cells.

1E) The concept tested is plasmolysis. The lab uses onion cells submerged in solutions of different concentrations (independent variable) in order to determine how much the cell wall would retract from the cellular membrane (dependent variable) as a response to the different concentrations.

1A) Diffusion is the random movement of the molecules from an area of higher concentration to an area of lower concentration. Osmosis is the diffusion of water through a selectively permeable membrane (a membrane that allows diffusion of certain solutes and water) from a region of higher water potential to a region of lower water potential. Water potential is the measure of free energy of water in a solution.

1B) A hypertonic solution is the one with less solute. A hypotonic is the one with more solute. Whether the solution is hypertonic or hypotonic determines the net movement of water.

1C) Water potential has 2 components: a physical pressure component and the effects of solutes.

Water Potential = Pressure Potential + Solute Potential

Water will always move from an area of higher water potential to an area of lower water potential.

1E) Plasmolysis is the shrinking of the cytoplasm of a plant cell in a response to diffusion of water out of the cell into a hypertonic solution surrounding the cell membrane. During plasmolysis the cell membrane pulls away from the cell wall.


1A) We took a dialysis bag and filled it with a solution made up of 15% glucose and 1% starch. Then we soaked it in the iodine solution. We used the urine strips to measure the glucose content, and then recorded the initial content and color. It was left to sit for 30 minutes . After, we measured the glucose again and recorded the results.

1B) We took 6 dialysis bags. Each bag had a different amount of sucrose in it, the sucrose went up increments of .2 mole . The first bag was distilled water and had 0 M. The sixth bag had 1.0 mole sucrose. After, the bags were filled with the sucrose they were weighed. Then each bag was put in beaker filled about 2/3 of the way with distilled water. We let the bags sit in the beaker for 30 minutes. After 30 minutes was up, we dried the remaining water off the bag and weighed them again. Last, we recorded the weight change.

1C) In this experiment we cored a potato to get 24 different pieces. We split up the potatoes between 6 beakers. Each beaker got 4 potatoes. After the potatoes were cut and split up, we weighed each group of potatoes. Then they were placed in their assigned beakers. Each beaker was filled with a different concentration of sucrose. The first beaker was distilled water and the beakers concentration of sucrose went up by .2 mole. The last beaker was filled 1.0 mole of sucrose. The beaker were left to sit for 1 day. The next day, we took the potatoes out of their beakers and dried them off. Then we weighed the potatoes again and recorded the data.

1E) In this experiment we cut 3 small pieces of onion epidermis. We observed the pieces of epidermis under 100x microscope. Then, we added 2 to 3 drops of 15% NaCl to the onion epidermis. Finally, we flooded the onion cell with fresh water, and then looked at the change in the cell under the microscope.



1A) By emerging the bag of 15% glucose & 1% starch into the beaker of H2O & IKI solution, the weight of the bag increased because iodine passed into the bag. This bag is a perfect demonstration of a selectively permeable membrane: it only lets glucose and iodine pass. Starch is not allowed to leave the bag, therefore there is no color change in the iodine solution. After letting the bag sit in the iodine solution for approximately thirty minutes, iodine eventually makes its way into the bag through its selectively permeable membrane, which explains the color changing from colorless to a deep blue. There was no chemical or color change in the iodine because the starch molecules were too large to fit through the membrane pores. Starch could not leave the bag and it's the only substance that would've effected it.IMG_2878.jpg
 IMG_2811.jpg Dialysis bag after sitting in the solution for 3o minutes.

1B: Dialysis Bag
Sugar molecules take up the most room in the bag, which leave a small amount of 'space' for water. Because water always strives for equilibrium, it constantly tries to diffuse into the bag, causing the bag's mass to increase. Osmosis occurs in this experiment because it is a type of passive diffusion, meaning it happens on its own. Water travels in and out of the membrane pores with the help of aquaporfins to reach equilibrium.When the bag of distilled water was emerged in distiller water, its mass went down because water was striving to reach equilibrium. It left the bag trying to equal it's self out, doing so by passing through the membrane pores. In an ideal trial of this experiment with no traces of sugar left on the bag, the mass would've stayed the same. Water + water = water therefore no major changes occurred. The 1M solution was the heaviest out of all of them because it contained the least amount of space for water (hypotonic) and it had the highest amount of sugar. Therefore the most amount of water has to go into the bag out of all of them. Osmosis is when water moves in and out the cell membrane. The water wants to equal out the concentration to reach equilibrium Osmosis is a type of passive diffusion, osmosis can be speed up by aquaporfins.

1C: Potato cores
The mass of the potato cores went down as the molarity of the solution went up. This happened because the molarity of the solutions were higher, water had to leave the potato in order to reach equilibrium. In the solution of the distilled water, the mass in fact went up because of the amount of the water in the solution. Since the solution was pure water with no sugar, the potato core was in a hypotonic solution. This means that water diffused into the potato cores, causing it's mass to go up, and it to become turgid. The solutions that were hypertonic to the potato such as 1M solution, water left the potato by osmosis. The mass went down and the became flaccid.IMG_7133.jpg

1E: Onion Cell
In this experiment  there were 3 onion cells . One onion cell was in plasmolysis . This is when the cells in hypertonic, the cell looks shrivels a. It becomes shriveled because water leaves the cell .The onion cell was  then flooded with water the cell became  turgid or hypotonic. Under the microscope the cell looked imploded.  It looked like that because for plants when they become hypotonic their cell walls push back , this is different from humans because when human cells become hypotonic they explode. Plants cells push back. The last onion cell become flaccid or isotonic. This is when the water content and the outside content are equal. The for humans this is a normal and good state to be in. For plants this is below normal levels, plants need to be in hypotonic. It is better for them to be bursting with water.IMG_2221.jpgIMG_2852.jpgIMG_0416.jpg Pink picture: Plasmolysis. Red picture: flaccid Blue picture: turgid
Conclusion- Conclusion

1A: During the 1A experiment , the results we collected showed us that glucose and iodine can pass through a selectively permeable membrane and will pass through when the concentrations are not equal.  This was shown when the color of the liquid in the bag turned from a color less to a dark blue.  The starch solution did not pass through the selectively permeable membrane into the bag because the starch molecules were too large.  We concluded this from the fact that the starch solution started out color less and after the 30 minutes of soaking remained color less.

1B: In The 1B experiment, the results showed that sucrose cannot pass through a selectively permeable membrane.  Instead the water move in and out of the membrane trying to reach equilibrium. This is done through osmosis I which is when water tries to equal out the concentration on either side of the selectively permeable membrane.

1C:  In the 1C experiment we concluded that potatoes contain sucrose molecules which make it unable to pass through a selectively permeable membrane. This was shown when the cores took in water while they were sitting in the water for 30 minutes.  We came to this conclusion when the onions weighed more after they sat in the distilled water. This means they contained less water and more solute potential than the distilled water, which is why the eater rushed in to try and reach equilibrium.

1E:  If we had done the 1E experiment, the onion cells would have plasmolyzed due to the addition of NaCl to the cells.  This shows that the onion cells had a higher water concentration that outside the cell.  This is why the water rushed out of the onion cell trying to equal out the water concentration.

Monday, September 30, 2013

Klaudia's Glacial Park Reflection

The trip to Glacial Park was very beneficial: not only were we learning about restoration ecology, we were also helping with the restoration process. The hands on experience allowed for better understanding of the topic as well as some outdoorsy fun. The hike up and down steep hills revealed beautiful scenery and resulted in some sore muscles the next day. After we had reached our destination, we were given glasses, gloves, saws, and loppers. Then, we were shown a site filled with invasive species that needed to be removed, and we got to work. We spent four hours sawing, lopping, pulling, and creating a burn pile of plants. The before and after pictures after just 30 minutes are quite impressive: 


I think the restoration process is necessary to make up for damage humans do not necessarily do to the specific site being restored but to the Earth in general. If it takes as long as 150 years to restore 3,500 acres with the help of restoration ecologists, then I would imagine it takes a lot longer to do it without their help.

Sunday, September 29, 2013

Caitlin's Thoughts On the Glacial Park Field Trip

          I only wanted to go on this field trip to be with my friends and not have to go to class that day honestly. Cutting down trees did not seem like my type of fun at all. Little did I know how glad I was that I went when it was all done.
         Upon arrival at Glacial Park, our group of all the AP Biology students at PHS were greeted by a man whose job was to restore the land in the park. He told us about how it took about one hundred years for Glacial Park to become destroyed and how it will take even longer to restore it. He mentioned that because of their hard work, many species have returned back to the area such as badgers. These animals had left when the park was on a decline, but have been able to return in the recent years because of the work put towards restoration.  The last thing he told us was what our tasks for the day were going to be. They did not seem exciting at all. 
        To reach our places of work for the day, our group took about a five minute hike through the park. It was gorgeous. We had to walk up one hill, and at the top you could see for miles and miles. All the plants were green and full of life. The weather was perfect, too. The sun was shining and there was a slight breeze in the air was we walked. My groupmates and I took many pictures on our IPads during the trek. 
        The first part of our work was cutting down evasive species and brush. Types of plants such as honeysuckle that are not native to the area had taken over the land. In an area where the brush had already been cleared, all the grasses were at about waist high level. In the area where we cleared, it started out crazy, overgrown, and very tall. There were random branches and plants all over the place. We had a lot of work ahead. Getting started was the worst part. We had no idea where to start. We soon realized that you just had to go at it with a saw and clippers. Everything was uprooted, cut, or sawed down to allow species native to the area to grow. All of the dead stuff we collected was put into a big stack which we called the 'burn pile'. This massive pile of branches and leaves was going to be burned to rid the area of it. Burning the area may seem like it would kill the stuff still living, but it actually helps it. The native species can actually survive the fires because they are immune to them from the open prairies back in the day. 
       The second part of our work took place in a very open part of the park. Little trees that had already started growing needed to be watered, so we did that. The little trees received a ridiculous amount of water compared to their size, but this would be their on drink of water for the next ten days. Next, we planted acorns similar to how squirrels would do it, but with little shovels. By planting these, we hoped that at least some of them would take root to grow even more trees. Lastly, a couple kids and I sprinkled seeds of prairie grass all over the area where the little trees were. We hoped that eventually the grass will grow and spread it's seeds all over even more of the land. 
View during the walk to our work spot
Watering a tree
        Overall, I thought it was a very fun day. Cutting down the trees was more entertaining and rewarding than planting acorns. I liked how you could instantly see the effect you had on the environment whereas I couldn't even see that day if my acorns took root. I had a great time outside, and am very glad we went.
Adding a branch to the burn pile