BIOLOGY 103 FALL, 2002 LAB 4

Measurments:

2micrometer bead-143 micrometers in movement
4micrometer bead-80.4 micrometers in movement
6micrometer bead-5micrometers in movement

Variables: due to the fact that i have a lazy eye and Mande has horrendous vision, keeping track of the bead proved difficult and may have had have effected our outcome.

Onion cell

Hypothesis: Adding water will create movement within the cell wall therefore causeing the cell membrane to expand (turgid), the addition of salt however will cause the membrane to retract within the cell wall.

Observations:
3% salt solution-all cells are turgid with noticible nucleus.
Distilled H2O- Cells are clear under scope, with turgid cells, noticable nucleus.
25% salt solution- Cell membrane appears smaller than cell wall(plasmolized), not all of the cells retain this plasmolized state, some are still turgid.

Conclusion:
Water molecule movement seems to be inhibited in some way by the addition of salt, because the cell membrane retracted within the cell wall, when salt was applied therefore implying that the water created movement within the cell hence swollen and retracted states of the membrane.

Movement in a thirty second period

2 microns: First Trial- 35 units (91 microns)
Second Trial- 22 units (57.2 microns)

4 microns: First Trial- 11 units (28.6 microns)
Second Trial- 14 units (36.4 microns)

8 microns: First Trial- no movement
Second Trial- 1 unit (2.6 microns)

This data supports the hypothesis that bigger molecules do not move as quickly as the smaller ones.

Onion Observations

3% solution- some plasmolyzed cells

Distilled Water- mostly turgid cells

25% solution- mostly plasmolyzed cells

Water fills up the cells because its molecules are lighter than salt's and move quicker. Distilled water has a lower viscosity than saltwater, so it can flow quicker into the cells.

2um............4 segments
4um............2 segments
8um............1 segments

all measurements were taken at the 40x power

the data suggests that the hypothesis is correct. the larger the bead the less it moves

onion data

3% salt.......turgid
H2O...........turgid
25% salt.......plasmolyzed

the data suggests that the presence of salt changes the cells.

Both observations combine to suggest that the cells are turgent with water because the movement of the molecules pushes the membrane, but when the salt is added the membrane becomes denser/heavier and so the water is unable to move it outwards to the cell wall.

Sarah Frayne
Stephanie Lane

Trial #2: We looked at what we think was 4 Micron beaded water, but we couldn't see it moving. Then we thought that we saw the molecules, but they were stationary. Then Will and Prof. Grobstein informed us that we did not have enough water on our slide, and so we tried again.

Trial #3: This time we were sure to put 4 Micron beaded water on the slide, and after again much playing wih the microscope, we were able to find the water molecules, which were moving, but very slowly, especially when compared to the movement of the 2 Micron water. The 4 Micron water moved about 109 micrometers in three minutes.

Trial #4: With the 8 Micron beaded water, we looked through the 'scope and saw that the molecules were hauling ass (it's an industry term) on the slide. When we expressed our surprise about this, Will informed us that perhaps we should look in again, and when we did, the molecules had slowed down significantly - in fact, they were hardly moving at all. We concluded that we had begun our observation too early and had not given the molecules tme to settle down. In three minutes, the 8 Micron water moved 44 micrometers.

The Onion Phenomenon

#1: With the 3% salt solution, several of the cells were plasmolyzed, and some are even empty (AAHH!!!). This is because Will overestimated the isotonic solution, which is the level of salt solution that is in perfect harmony with the cells (bad Will.) This may also be because we chose as our subject the outermost layer of the onion, which Will says may be closer to death. Perhaps our obervations would have been different if we had chosen a layer of onion closer to the core.

#2: After adding the water, all of the cells appeared to be empty. However, we have learned that this clear and empty appearance is somewhat deceptive. All of the cells were turgid, and Will was wrong when he told us that the cells were really plasmolyzed. After reducing the light source and focusing in a little closer, we could see the green chloroplasm along the cell wall, and a nucleus in almost every cell.

#3: After adding the 25% salt solution, we found that a large percent of the cell membranes have been plasmolyzed. This would lead us to believe that the more salt which is present, the more plasmolyzed the cells become.

OConclusions: Because the cells were the most turgid when immersed in the pure water solution, the NaCl is therefore responsible for the collapse of the Cell Membranes. We hypothesize this occurs because the NaCl has an averse reaction to the water: when the onion sample is immersed in the pure water solution, the molecules move faster and therefore become turgid enough to fill the entire space of the cell wall. Because when NaCl is present, the cell membrane shrinks away from the cell wall, we think that the salt causes the molecules to move slower, thereby making it unable to become completely turgid.

Hypothesis: Our idea was that in water, big beads would move less than smaller beads following the principle that the water molecules are also moving.

We observed different sized beads in water and measured the largest radius covered by each over a period of four minutes.

8 micron beads: largest radius covered 18.2 micrometers
4 micron beads: largest radius covered 24.3 micrometers
2 micron beads: largest radius covered 33.8 micrometers

Our observations supported our hypothesis and so we will use these observations to aid explaination of the onion and water/salt solutions.

The onion cells with 3% salt solution showed primarily turgid cells with a few beginning to plasmolyze with the corners of their cell membranes pulling away from the cell wall.

The onion cells in water (distilled H20) were completely swollen, all cells are turgid.

The onion cells in the concentrated 25% salt solution are plasmolyzed. The cell membranes appear squished and shrunken within the cell walls.

So to explain this phenomena and what it has to do with the beads...
Both observations prove that water is in constant motion.
Our observations with the onion showed us the different ways that cells look with different concentrations of water and salt.

Our idea is that the concentration of salt in the water effects the degree to which water moves in and around the cell. Just like the size of the beads effected how much they moved.

So our next course of action would be to determine what the degree of water movement has to do with the appearance of the cell. Hopefully this would have something to do with density, but maybe not.

This exercise has challenged us in many ways and we realize that our final obersations are inconclusive, leading us to be wrong, yet again.

data:

bead size............maximum radial distance
2 um.................156um
4um..................15.6um
8um..................7.8um

conclusion: the data supports the hypothesis, leading us to believe that the larger the bead, the shorter the distance it will move. however, since we only did one trial of each bead size, these data may not reflect an actual trend.
-------------------
Procedure:
Prepared onion slide with one-cell layer.
When we looked at the onion cells in a 3% salt solution, the cell membranes and cell walls were quite close to each other, and the cells were turgent. When we looked at the cells after changing to a 25% solution, the cell membranes had drastically pulled away from the cell walls, and the cell itself had shrunk.

Given our new observations that water molecules are always in motion, we hypothesize that the cells shrank in the 25% salt solution because the water molecules had a smaller radial distance than when the cells were in a pure water solution, in which case the radial distance increased. We would like to take this lab to be one of our times to be wrong every day.

In the slide of the onion with 3 percent saltwater, we observed some shriveling of the membranes. When the distilled water was added, there cell membrane swelled to where they were turgid. When the 25 percent solution was added, there was severe shriveling of the membaranes. From this we concluded that the amount of salt in the water determines the amount of contraction of the cell membrane.

From both activities, we can conclude that water particles are always moving. Water caused the onion cell membranes to move; when the water was replaced by the salt, there was a moving in of the membrane, not a swelling out.

Christine Traversi
M.R.

Bead Size Distance Traveled
8 micrometer 10 micrometers

4 micrometers 104 micrometers

2 micrometers 13 micrometers

Onions

3% salt solution-> most cells are turgid, but some cells are plasmolyzed

0% salt solution-> more cells are turgid than plasmolyzed

25% salt solution-> most cells are asignificantly plasmolyzed.

Observations-
1. Water molecules are constantly in motion.
2. The quantiy of salt directly affects the distance traveled by water molecules.
3. Perhaps salt molecules are bigger.

Hypothesis: The smaller the microsphere; the faster its motion.

Methods: We took a special slide which had depressions on either side to act as a reservoir for any liquid that we would place there. After putting a specific liquid in the reservoir we covered it up with a cover slip and put the slide on the stage of the microscope to determine our observations. In this case we are supposed to measure the speed of the liquid molecules which can be found by measuring the distance a certain molecule moves in a fixed period of time since speed is distance divided by time. We used 2 minutes as the time for observation.

Observations 1:
1) 2 micrometer bead moved 30 micrometers in 2 minutes.
2) 4 micrometer bead moved 21 micrometers in 2 minutes.
3) 8 micrometer bead moved 1 micrometer in 2 minutes.

Conclusion: Sadly, we were right. Thus the smaller the size of the microsphere the faster it seemed to move. We believe that our conclusion is correct because it follows that a smaller molecule when bombarded by other moving molecules will move faster because the energy generated by the impact will cause the molecule to move faster.

Observations 2:
An onion membrane was placed on the slide and 3% salt water was dropped on it. The onion cells turned turgid. Next, distilled water was put on the same membrane and it was observed that the cells turned more turgid. 25% salt water was next added to the membrane and plasmolysis of the onion cells were observed.

Relating observations 1 and 2 we can say that the molecules moved from inside the onion cell to the outside area because the outside area had a higher concentration. We observed that as the added solution became more concentrated the cells became more plasmolyzed. In the higher concentration of solvent the number of molecules increased in each group (as the molecules bombarded each other they clustered together in groups) and therefore the groups moved more slowly.

These experiments have successfully demonstrated both brownian motion and osmosis.

Our findings support the thesis that says that water molecules are continuously moving, and the smaller the object was the more it moved.

Experiment 2:

3% salt solution made almost all of the cells turgid but a few of them were partially plasmolyzed.
0% salt solution made the cells even more turgid, and filled out the ones that were plasmolyzed earlier.
25% salt solution made the cells very plasmolyzed.

When there is salt in the environment outside of the cell, it takes water away from the inside of the cell, making the cell plasmolyzed. This relates to the hypothesis we supported in our last experiment (that water molecules are always moving whether we can see them or not) because the water was moving from the inside of the cell to outside of the cell, or vice versa.

Maggie Scott-Weathers and Emily Senerth

Onion Cell Observations:

In 3% solution the onion cells are pretty much turgid, and there is not much change from the cell appearance when the 3% solution is changed to distilled water, which has a 0% salt content. However, when the distilled water is replced by the 25% solution a majority of the cells become plasmolyzed.

Onion Cell Story:

When salt is introduced to the surrounding environment, the NaCl molecules are too big to pass through the cell wall. Therefore, to create equilibrium, water leaves the cell into it's surrounding environment. A cell is turgid when it has many water molecules in it because the water molecules move around and stretch the cell membrane to its capacity. This is the case in the distilled water solution. When salt is introduced to the cell's environment and water leaves the cell there are not as many water molecules to move around and thus the cell membrane "shrinks" and is not stretched to its capacity. The more concentrated the salt solution the more water exits the cell and thus the fewer water molecules inside the cell which makes the cell more plasmolyzed.

Experiment #2 Plant cells under three different conditions:
Th onion with the 3% salt solution showed all turgid cells. After replacing the solution with distilled water, not notced no change in the cell walls and membrane. We then replaced this solution with a 25% salt solution. We noticed that this solution caused the cell membranes to shrink, or to pull away from the cell wall.

Conclusion: In a higher salt concentration solution, we observed that the cells are all plasmalyzed. This is because the salt ions absorb the water molecules, which causes the actual membrane to shrink. Water is necessary to sustain the shape and structure of the cell membrane (in a plant cell, the cell wall will not move).

Microspheres
2m beads moved ~30 microns
4m beads moved ~13-15.6 microns
8m beads couldn't be seen moving

Onion Skin
distilled water saturated had mostly turgid cells
3% NaCl(q) saturated had some turgid cells and some plasmolyzed cells
25% NaCl(q) saturated had mostly plasmolyzed cells

The vacuoles of the cell filled with water when saturated with distilled water. This made the cell bigger and pushed its mebrane up against its cell wall (turgid). When we added 3% NaCl solution, water escaped the vacuoles and cell membrane as salt came into the cell, trying to equalized the salt level inside and outside the cell. This made the cells smaller and the membrane recede from the cell wall. When we added the 25% NaCl solution even more water was required outside the cell to equalize the salt levels in and out of the cell, making the individual cells more plasmolyzed.
Microbeads and onions are connected...

Observations: The 2micrometer bead moved a total of 20.8 ums away from its point of origin. The 4 micrometer bead moved a total of only 1.4 ums away from its point of origin. The 8 micrometer bed moved only .75 ums in total.

In the second half of the lab, we watched the cells of an onion react with different levels of salt within water. When the cells were placed in the 3% salt solution, we noticed that the cells' membranes were mostly turgid, although is some of the coners of the cells, there was slight plasmolyzation. In the distilled water, the cells were completely turgid, and fianlly in the 25% solution, the cells became very plasmolyzed, with the membranes clumpy together, pulling all the internal organelles closer together within the cell wall. (The wall itslef does not move).

Therefore, given these observations and our previous observations, we have found the meaning of life and the orgin of clumpy diversity.

The membrane retracting from the wall is a consequence of its interaction with the salt, an interaction due to the fact that water continually moves and passes through the membrane.

Once upon a time there was not a whole lot of salt in the ocean, right? That is analogous to the distilled water, so the cell (ie the earth's diversity) was turgid (and the reason for that more species and variations can exsist in distilled H2O then in the salt solution). THEN, salt slowly began to be more prevalent in the ocean and along with this, there came a little tiny bit of plasmolyzity (ie, clumpiness, because some of the intermediary species, like perhpas Heterotrophs with cell walls, couldn't manage). Even more salt came, and so the end result, which is the plasma all being CLUMPED together in the middle of the cell, was that all of the intermediary species that didn't work became extinct, and what you have left is clumpiness.


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