BIO1120L Expieriment 3 PDF

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Experiment lab 3: Osmosis and Diffusion...

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Buckner, 1 Lindsey Buckner BIO-1120L-01 Mike McKean February 8, 2021 Osmosis and Diffusion Introduction: Osmosis is when water is the molecule moving down a concentration gradient. Osmosis requires the presence of a semipermeable membrane. When a solution has a balance of water leaving and exiting the cell, the solution is called isotonic. All solutions move towards a homeostasis environment; isotonic. When there is too much water in a solution, the cell walls expand creating a hypotonic solution. When there is not enough water in a solution, the cell wall shrinks creating a hypertonic solution. In this lab, Osmosis and diffusion is tested in two different procedures: Osmosis and diffusion in plant cells, and Osmosis and Diffusion in protist cells.

Materials and Methods: Step 1: 1. Obtain seven large test tubes labeled 0, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8. Place 5 mL of different ranging concentrations of glucose (0-0.8 M). 2. Use a cork to obtain 7 pieces of potato that are the length of approximately 3 cm. 3. Use a paper towel to remove excess water before placing potatoe slices into the test tubes 4. Weigh each slice of potato and document it. After weighing each slice, place one slice in a tube of glucose concentration 5. Incubate all sevel potato samples for approximately 45 minutes. Gently swirl each test tube for 10-15 minutes. 6. Remove the potato pieces one tube at a time. Use a paper towel to gently absorb excess moisture. Record the potato pieces final weight and discard the sample when completed.

Buckner, 2 Step 2: 1. Obtain a clean slide and place a drop of amoeba on your slide. Cover the slide with a coverslip. 2. View the amoeba at 40x objective 3. Note the approximate size and shape of the amoeba and the contractile vacuole(s). 4. Add 3% NaCl solution drop. Observe the amoeba and notate the effects of the salt solution on the contractile vacuole(s). 5. Finally, add a distilled water solution. Observe and notate the effects of the water with the amoeba and vacuoles. -

In this experiment, it is noted to add a red solution to see the amoeba better under the microscope. In this experiment the staining has been disregarded.

Results: Table 3.1 Glucose (M)

Initial Weight (g)/Time

Final Weight (g)/ Time

Percent Change

0

1.77

1.85

104%

0.2

1.64

1.65

100%

0.3

1.69

1.65

97%

0.4

1.7

1.59

93%

0.5

1.74

1.59

91%

0.6

1.66

1.44

86%

0.8

1.6

1.34

83%

**Graphs for this data are represented below**

Buckner, 3 **The red line represents final weights and blue line represent initial weight**

Buckner, 4 Table 3.2: Amoeba 1 Condition

Size of Amoeba

Size of Contractile Vacuole(s)

Start- Water

130 mm

15 mm

Notes

-

3% NaCl added

90 mm

10 mm

-

Water added

60 mm

5 mm

-

-

-

Before the salt solution was added, amoeba was about 100mm. Moves very quickly, long and creates few pseudopods. Amoeba started to form more pseudopods Amoeba started to move slowly Amoeba pseudopod burst open and content came out Amoeba was around 60 mm when distilled water was added back to solution The amoeba leaked more content which can be assumed the cell wall burst The amoeba died

In step two, the first Amoeba died due to the solution becoming hypertonic too quickly. Adding salt caused a hypertonic solution. The cell wall caved in quickly on the amoeba which explains why one of the pseudopods burst. After the pseudopod burst, distilled water was added back to the solution. Adding water will either create an isotonic solution but if too much is added, the solution will become hypotonic. After water was added back to the Amoeba, the cells contents continued to leak out of the cell wall which can be assumed the solution at this point became hypotonic. When a solution becomes too hypotonic, the cell wall will buist and the cell will die which was the result of the first amoeba .

Buckner, 5 Table 3.2: Amoeba 2 Condition

Size of Amoeba

Size of Contractile Vacuole(s)

Notes

Start- Water

120 mm

10mm

-

Amoeba was viewed at 10x objective and measurements were taken at 40x objective

3% NaCl added

75 mm

0.7 mm

-

Amoeba contracted Formed more pseudopods Moved more slowly than without salt solution Only one drop of sodium solution was added to amoeba

-

-

Water added

100 mm

10 mm

-

-

-

Started to move faster Tried to form original shape before salt was added Created less pseudopods At very end observations, contractile vacuole measured about 5 mm

All measurements of amoeba size and contractile vacuole are only estimates as it is hard to measure accurately through a computer screen. This is where error could be calculated.

Conclusions: In step 1, the hypotonic solutions were test tubes 0. The percentage change of the initial weight and final weight was 104%. There was no glucose to mix with the potato therefore water was only entering the membrane creating a hypotonic solution. The isotonic solution in this experiment was glucose molarity of 0.2. The initial weight was 1.64g and the final weight was 1.65g. A difference of .01 gram constitutes the 0.2 glucose solution as an isotonic solution. The rest of the solutions were hypertonic. The rest of the solutions were hypertonic because the final weight was less than the initial weight signifying water was leaving the potato samples creating a hypertonic solution. If the glucose solution had a 5℃ temperature increase, the results could be different. When you cook potatoes, they become softer and more permeable to water absorption. If the glucose solution was

Buckner, 6 warmer, it would cause the potato samples to increase in temperature causing a difference in results. This is only a hypothesis as this hasn't been tested in the experiment. Another hypothesis to think about is if we used animal cells rather than plant cells in step 1. If we were to use animal cells, the initial and final weight is predicted to be different however the results would be similar. One thing that is not being taken into consideration in this hypothesis is if animal cells have a stronger cell wall than plant cells. Animal cells are also not as permeable as plant cells which could also create different outcomes. If 5% glucose was used as a maintenance fluid for patients unable to drink water, the solution would be hypotonic compared to the red blood cells. If someone is given fluids because they are unable to drink it can be assumed they are unable to eat. The body breaks down sugar for energy; glucose is sugar. If the patient is unable to drink it can be assumed they are dehydrated meaning their cells are hypertonic. To try to balance this out and create homeostasis, the patient would need a hypotonic solution to created a balanced isotonic internal state. To conclude results with step 2, if the amoeba was placed in a higher salt concentration, the amoeba would die. The first amoeba in step 2 died because the internal state of the cell became too unstable. It can be assumed when the sodium solution was added, the amoeba’s cell wall contracted too quickly causing the cell wall to collapse. When water was added back to the solution, the amoeba expanded too quickly causing the rest of the cell wall to burst and allowing the internal organelles to seep out. Cells have to live in an isotonic state. If cells become too hypotonic or hypertonic, they will die. This is why it is important to make sure organisms stay hydrated. It is also important that an organism has balanced sodium levels, as too much sodium dehydrates....