Cell Communication Lab

Purpose

The purpose of this lab was to investigate cell signaling between two strains of yeast- a-type and alpha-type. We observed the mating interactions between the two. 

Introduction

Cell-to-cell communication, or cell signaling is an important function of cells. It occurs within multicellular organisms and between unicellular organisms. Cells can communicate with each other a few different ways, although the most popular way is via chemical signals. Yeast, also known to the science world as Saccharmoyces cerevisiae, has two mating types as mentioned earlier. The two different types communicate with each other through signal transduction pathways via secreted factors. A signal transduction pathway is a series of steps in which a message received at the cells surface is amplified through transduction which then triggers a response. In yeast cells, a-type cells have receptors that receive chemical signals from alpha-type cells. Alpha-type cells also have receptors that receive chemical signals from a-type cells. That way, when they secrete their own chemical factor, the opposite type is able to receive it. Once the two yeast cells receive the signaling factor from the other type, they begin to change their cytoskeleton in order to "grow" toward their mate. This elongation of the cell is called a shmoo. 

Yeasts can reproduce sexually and asexually. In asexual reproduction, also known as cell division, both the a-type cells and alpha-type cells bud in order to produce daughter cells, or haploids. In yeast, the haploid cell can turn from an asexually reproducing cell to a gamete, or sex cell. The yeasts then stop dividing and grow into their gamete shmoo form. the yeast begin to grow toward their partner and fuse together. When the two types come together, they form a diploid zygote. 

We used a toothpick to pick up a colony of each type of subcultures of yeast and put them into their designated culture tube filled with 2mL of sterile water.

We used a transfer pipet to transfer 5 drops of yeast suspensions onto their designated plates.

Data:

Discussion
In this lab, cell communication among yeast cells were observed. There were many differences observed between the alpha type and a type strains. In the alpha-type strains, there were more budding haploid cells than in the a-type. When looking at the graphs of both the cultures, we saw that the two had several similarities in the amount of cells between the a type and alpha type cultures. The outcome showed that more budding haploid cells were seen in the alpha type than in the a type. In the alpha type, there was a much bigger percentage of budding haploid cells (12.5%) than in the a type (5%). However, when looking at the graphs for the single haploid cells, the alpha type had a lower percentage than the a type. (87.5% versus 95 %) When observing the mixed culture, which was the alpha types cells over the a type cells, we expected to see lots of budding haploid cells from the a type, and also lots of single haploid cells due to the high percentages that both the alpha type and a type had when discussing the percentage total of single haploid cells. The hypothesis was correct. When looking at the mixed culture under the microscope, it was the most abundant amount of cells observed from the three types we had looked at. Yeast cells most likely commnicate using both direct contact and pheromones. The pheremones sent help yeast spot that there is a potential mate near them, which they grow towards and then create a shmoo. Then the cellular response reacts to turn the cell into a sex cell. Direct contact signaling allows the shmoos to send a signal to create a baby (zygote).

Conclusion
In this lab, the purpose was to observe cell signaling in three different types of yeast. Looking back at the results of the expirament, it appears that the alpha type yeast has more of a mating signal released than the a-type cells. This is concluded due to the much higher percentage of budding haploid cells than type a had. Our mixed culture had the most asexual reproduction activity, which shows that the different types of yeast can communicate with eachother using direct contact and pheremones.

Photosynthesis/Light Reaction Lab

Purpose

The purpose of this lab was to prove that light and chloroplasts are required for the light reactions of photosynthesis to occur.

Introduction

Photosynthesis is a way for plants to make their own food using direct sunlight. Photosynthesis occurs in plants, algae, certain other protists, and some prokaryotes. Leaves are the major locations of photosynthesis; where chloroplasts are located. In order for plants to produce sugar and release oxygen, they must first go through the light reactions. Chloroplasts split water into hydrogen and oxygen, incorporating the electrons of hydrogen. Light is then absorbed and the energy is used to drive electrons from water to generate NADPH, a stored sugar. When the electrons are excited, they burst upward and are caught by an electron accepter and then slowly released down via the electron transport chain. It is important to understand the job of the electron acceptor. DPIP can also be used instead of NADP. Every time the electrons in the chloroplast become excited, they will reduce DPIP. This will cause DPIP to change from blue to colorless. 

Methods 

Pipette 5mL of 100% dye solution into the 1st test tube, and pipette 2.5 mL of distilled water into the remaining 5 test tubes. 

Then transfer 2.5 mL of dye to the 2nd test tube and mix well. 

Transfer 2.5 mL of solution from the 2nd rest tube into the 3rd test tube and continue the process for the remaining test tubes. 

We filled a cuvette with solution from test tube 1 and read the Abs. and %T. We continued the same thing for the rest of the text tubes.

Graphs and Data

Discussion

In this lab, light and chloroplasts are proven to be needed for light reactions in photosynthesis. DPIP is used instead of NADP, which is the electron accepter in this experiment. When the electrons become excited, they will reduce the DPIP supply. These electrons come from the breaking down of light energy and water. The reduction of the DPIP supply will cause the solution to change from blue to clear. Due to the DPIP reduction, light transmittance is given off. This can be measured using a spectrophotometer, which measures the percentage of light transmittance. When the DPIP is placed in darkness, there is no reduction in it because the electrons cannot be excited because they do not have any light to excite the electrons. When the chloroplasts were boiled, it denatured the protein molecules, which also stopped reduction in the DPIP. There was a difference in percent transmittance of the unboiled chloroplasts that were in the light and the dark. This is because in the dark cuvette, there was no light, which meant that there was no light energy and therefore no breaking down of light and water which meant that the electrons could  not be excited. In the lighted cuvette, there was light energy, which aloud breaking down of light and water and therefore there were excited electrons.

Conclusion

The experiment preformed showed that chloroplasts and light are necessities for light reactions in the photosynthesis process. All in all, the outcome of the data proved this point true. It showed all factors of boiling, denaturing, and darkness, which did not allow light reactions to occur.





Cell Respiration Lab

Purpose

The purpose of this lab is to measure the amount of carbon dioxide released by cellular respiration by marbles, non-germinated peas, germinated peas, and germinated peas at a cool temperature.  

Introduction

Cell respiration is the process of oxidizing food molecules, like glucose, to carbon dioxide and water. It is represented by the equation: C₆H₁₂O₆ + 6O₂ + 6H₂O → 12H₂O + 6 CO_{2.  In cell respiration, chemical energy from "food" molecules is released and partially captured in the form of ATP. Carbohydrates, fats, and proteins can all be used as fuel for cell respiration, however glucose is the most common. Cells take the carbohydrate into their cytoplasm, and through a complex series of metabolic processes, they break down the carbohydrate and release energy in the form of ATP. When cells to go through cell respiration, they take in oxygen and release carbon dioxide.} 

First we put 25 marbles into the respiration chamber.

        

Then we put 25 non-germinating peas in the respiration chamber and recorded the amount of CO_{2 produced in 10 minutes.}

We then did the same process but with germinating peas.

We soaked the germinating peas in ice water for 5 minutes.

We blotted them dry and put them into the respiration chamber again.

Lastly, we tested the cold germinating peas in the respiration chamber for 10 minutes again.

Data:

Graphs:

Discussion

In this experiment, marbles, non-germinating peas, and germinating peas at different temperatures were tested for their particular rates of cell respiration. In testing the non-germinating peas in contrast to the germinating peas, data showed that germination greatly accelerated the rate of cell respiration. This shows a greater rate of metabolic activity in germinating peas versus non-germinating peas. The non-germinating peas showed very little activity, with only about .02 for the rate of respiration. When testing the peas dunked in cold water versus the peas that were at room temperature, the warmer peas showed an increase in respiration in contrast to the cold peas. The germinating peas respirate more than the dormant peas because the pea needs energy for the growth that is happening, something that is not needed in the dormant pea.  

Conclusion

This lab presents the different rates of respiration based on different organisms. It was found that

germinating peas respirate at a higher level than dormant peas.

Enzyme Catalysis Lab

Purpose:
The purpose of this experiment was to observe the conversion of hydrogen dioxide to water and oxygen gas by the enzyme catalase, and measure the amount of oxygen generated and calculate the rate of the enzyme-catalyzed reaction. We basically had to observe and understand the effects of changes in temperature, pH, enzyme concentration, and substrate concentration on the reaction rate of an enzyme-catalyzed reaction, and also to understand how environmental factors affect the rate of enzyme-catalyzed reactions.

Intro:
Enzymes are proteins produced by living cells. They are biochemical catalysts meaning they lower the activation energy needed for a biochemical reaction to occur. The substrate is the substance acted upon in an enzyme-catalyzed reaction, and it can bind reversibly to the active site of the enzyme. The active site is the portion of the enzyme that interacts with the substrate so that any substrate that blocks or changes the shape of the active sit effects the activity of the enzyme. The result of this temporary union is a reduction in the amount of energy required to activate the reaction of the substrate molecule so that products are formed. The enzyme is not changed in the reaction and can be recycled to break down additional substrate molecules. The enzyme used in this lab is catalase. One catalase function is to prevent the accumulation of toxic levels of hydrogen peroxide formed as a by-product of metabolic processes. The decomposition of hydrogen peroxide to form water and oxygen: 2 H2O2 → 2 H2O + O2 (gas) Without catalase this reaction occurs spontaneously but very slowly. Catalase speeds up the reaction notably.

Methods:

First we put 10 mL of 1.5% H2O2, and then added 1 mL of catalase extract and swirled it gently for 10 seconds. At 10 seconds,we added 10 mL of H2SO4. The same thing was done six more times but with intervals of 30, 60, 90, 120, 180, and 360 seconds before adding the H2SO4. 

 

 For each solution a 5mL sample was taken and put it into a fresh beaker and added drops of KMnO4 until the solution became colored.

Data

Finding our baseline (uncatalyzed) reading

*note our 10 second trial is miscalculated due to our error

Graph

Discussion

The rate of the reaction is calculated by measuring, over time, the disappearance of the substrate, which can be measured by seeing when the appearance changes of the product. The rate, in the experiment, is the highest from the initial to ten, because the hydrogen peroxide had been exposed to the air for the least amount of time. It's lowest rate was when the hydrogen had been exposed to the air longer. This is because the longer the hydrogen peroxide is exposed to air the more broken down it becomes, and therefore, weaker. The sulfuric acid has an inhibiting effect on the catalase's function because it causes the pH level in the solution to lower a considerable amount. Acidic solutions result in the protein structure of the enzyme to gain hydrogen ions which causes it to denature, which stops the reaction immediately. Lowering the temperature in this experiment would cause the reaction to slow down due to enzymes working best in normal temperature. If the temperature were lowered a larger amount, for example lower than 37 degrees celcius, it would be denatured and not be able to react anymore. Although this experiment was as controlled as possible, several things could have been controlled better. In some instances, too much KMnO4, resulting in a redo. Watching the reaction of the solution to the KMnO4 is not very controlled due to the fact that different people see different things. What one person sees as a change of color another may not. 

                                                                        Conclusion

This lab presents how changes in temperature, pH, substate concentration and enzyme concentration can effect the reaction rate of an enzyme catalyzed reaction. Our observations of the amount of oxygen produced in comparison to the rate of the enzyme catalyzed reaction showed how the environment can drastically effect the rate of the reaction. .

Diffusion and Osmosis Lab

1A- Diffusion 

Purpose

The purpose of this lab was to understand the mechanisms of diffusion and to notice the effects of a selectively permeable membrane on diffusion between two solutions separated by the membrane. 

Introduction

Diffusion is defined as the random movement of molecules from an area of high concentration of solute to an area of low concentration of solute. For example, if someone were to spray Axe Body Spray in the corner of a classroom, eventually everyone in the classroom would also be able to smell it because the particles would disperse evenly throughout the room. A semipermeable membrane, or selectively permeable membrane, is a membrane that only allows certain solutes and water to pass through it. The movement of a solute through a semipermeable membrane is called dialysis. In dialysis, smaller molecules will pass through the membrane easily, while larger ones will take a longer period of time, or won't pass through at all. 

Methods

.

First we cut a piece of dialysis tubing.

Then we soaked the dialysis tubing in water so that it would soften and we would be able to open it. After opening it, we tied off one end with a rubber band. 

Next we added 15 mL of a 15% glucose/1% starch solution into the bag. 

Before tying off the bag, we tested the solution for the presence of glucose. The solution tested positive because it was 15% glucose/1% starch.

Then we put a solution of  iodine and water into a beaker and tested it for the presence of glucose. It tested negative because it consisted of water and iodine. 

The solution in the bag was initially clear (15% glucose/1% starch) and the beaker was a red orange color (iodine and water).

Then we placed the bag in the iodine solution and let it sit for 30 minutes. 

After 30 minutes, both the solution in the bag and in the beaker changed colors.

Presence of glucose test in the cup before and after the experiment. 

Presence of glucose test in the bag before and after the experiment.


Data

 Discussion

This experiment clearly displayed diffusion of substances through a selectively permeable membrane. In our initial experiment (before we put the bag of 15% glucose/1% starch into the iodine water solution) the bag tested positive for glucose and the beaker tested negative. However after the hydrolysis bag soaked in the solution for 30 minutes, both the bag and the beaker tested positive for the presence of glucose. This means that through the process of diffusion, the 15% glucose/1% starch solute moved out of the bag while water and iodine moved into the bag. The inside of the bag contained a high concentration of solute (15% glucose/1% starch) while outside the bag contained a low concentration. On the other hand, the outside of the bag contained a high concentration of iodine while the inside of the bag contained a low concentration of iodine. Looking at our results, the bag drastically changed colors from clear to a dark purple whereas the beaker changed from a red orange to a lighter shade of red orange. From this we can conclude that the membrane contained pores that better fit the iodine molecules than those of the 15% glucose/1% starch solution. It was easier for the iodine molecules to pass through the membrane which caused the inside of the bag to become so dark. Although the 15% glucose/1% starch molecules still must have passed through the membrane but at a much slower rate. The iodine molecules had to have been smaller than the pores of the membrane which must have been smaller than the glucose molecules. Because of this diffusion was able to occur through the membrane but at different rates for different substances. 

Conclusion

Because membranes are semipermeable, different substances diffuse at different rates or not at all. Diffusion occurs when solutes move from an area of high concentration to an area of low. Because the dialysis bag membrane was more permeable to the iodine molecules, the bag turned a darker color than the original beaker. Although through the much slower diffusion of 15% glucose/1% starch molecules, both the cup and the bag tested positive for the presence of glucose. 

Experiment 1B:


Purpose:
The purpose of this experiment was to investigate the relationship between solute and concentration and the movement of water through a selectively permeable membrane by the process of osmosis.

Introduction:
A selectively permeable cell membrane is one that allows certain molecules or ions to pass through it by means of active or passive transport. Selectively permeable membranes can be found around a variety of cells and places. All cell membranes are selectively permeable. This means that water can cross these membranes by osmosis. Osmosis do the diffusion of water. This will happen when the total concentration of solutes on one side of the membrane is different from that on the other side. When two solutions have the same concentration of salutes they are said to be isotonic to each other. If the two solutions are separated by a selectively permeable membrane, water will move between the two solutions, but there will be no net change in the amount of water in either solution.

Methods:
There were six bags filled with approximately 15ml of different solutions. One bag wag filled with distilled water, one with 0.2M sucrose, one with 0.4M sucrose, one with 0.6M sucrose, one with 0.8M sucrose, and one with 1.0M sucrose. After taking the mass of each bag, the bags were placed in different cups filled two thirds of the way full of distilled water. After thirty minutes, the bags were taken out, dried, and massed separately.

Data:

Graphs and Charts:

Discussion:

Solutions that are hyper tonic have more solute and therefore less water. All of these solutions are hypertonic because they gained mass because water rushed in, in order to reach equilibrium. The one solution that was isotonic was the 0.4M sucrose solution. The change in mass and the molarity of sucrose within the dialysis bags are directly proportional. As the mass increases, so does the molarity. If all the bags were placed in a 0.4M sucrose solution instead of distilled water they would be inversely proportional because whenever the sucrose molarity inside the bag is more concentrated, it will become more dilute and vise versa. The solutions will reach equilibrium somewhere between the two concentrations.

Conclusion:

This lab proved that water moves across the selectively permeable membrane much easier than sucrose does. The water moved to reach equilibrium between the solutions. Sucrose must be too large a molecule to pass through the membrane quickly.

Experiment 1C: Water Potential

Purpose-

The purpose of this experiment was to determine the water potential of potato cells.

Introduction- 

The term water potential is used to determine the movement of water when entering or exiting a plant cell. The process has two main parts, the effect of the solute (solute potential) and the physical pressure (pressure potential). Water moves from places with higher water potential to areas with lower water potential. This is because areas with higher water potential have more molecules in it while lower water potential areas have less molecules in it. It is almost like when people gravitate to areas that are less crowded during an event. Movement is also determined by the solute potential on both sides of the cell membrane. When water moves into the cell, the cell expands, when it moves out, the cell shrinks. This is why plants that are experiencing droughts are wilting, while plants in the grocery store that are always being watered are sturdy and green. 

Methods-

There were 5 cups filled with their assigned morality of sucrose, .2 M, .4 M, .6 M, .8 M, and 1.0 M, and one cup with distiller water. There were 4 potato cylinders for each beaker. The masses were recorded for each group of 4 potato cylinders. After, the four potato cylinders were placed into their chosen solutions. After a day, the potato cylinders were removed from the solutions and patted dry on paper towels. Then, each group of four potato cylinders was massed once again. 

Data-

Discussion-

Water potential values allows to predict the flow of water into or out of a plant cell. As any plant dehydrates, so lutes become more concentrated, so the solute potential becomes more negative, that means that the water potential would decrease as well, becoming more negative. The less water in a plant means the less water potential. When a plant cell has lower water potential, which means less water and more salutes, it is hypertonic to its surroundings. This means the plant cell gains water when in a hypertonic state, because water moves from higher water concentration to lower. 

Conclusion- 

The lab showed that the potato cores had more water in them the day after the experiment than their original state. The water did so because the potato had less water concentration than the surrounding solution.