Melia Cordero- Membrane Transport unit write up

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Feb 20, 2024

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MCB181L Membrane Transport Unit Write-Up ______________________________________________________________________________ Initial Observations: Elodea in freshwater seemed to have moderate movement. We were able to observe clear and organized rectangular cell walls and very distinct chloroplasts. The chloroplasts seem to clump into groups within the cell as well as spread out in other parts. Interpretation: Due to the moderate amount of movement observed, we can conclude that there is diffusion or osmosis occurring between the cell and the surrounding freshwater. Considering the cells are large and plump we can infer that the freshwater is hypotonic in relation to the concentration inside of the cell. Elodea in 150 mM NaCl had less movement than in the freshwater cell. The chloroplasts appeared to be smaller and slightly more spread out

MCB181L compared to fresh water. The cell wall was darker and more apparent within this sample. Interpretation: Elodea in 150 mM NaCl had less movement than freshwater which could be since the 150 mM NaCl solution is isotonic in relativity to the inside of the elodea cell. If there is an equal amount of concentration between the inside and outside of the cell that would explain the lack of movement. When we observed elodea in 400 mM NaCl the chloroplasts tended to clump up the most under these conditions. The cell walls started to warp from their rectangular shape to a rounder edge. Interpretation: When observing the Elodea in 400 mM NaCl there was a significant difference in the shape of the cells. The cell walls seemed to be warped and the chloroplasts seemed more grouped together. With this information, we can infer that the 400mM NaCl is hypertonic in relation to the inside of the elodea cell. The net movement of water is out of the cell into the surroundings which results in a more shriveled up shape of the cell. Initial Model:

MCB181L Our initial model shows the net movement of solution between the elodea in freshwater, elodea in 150mM NaCl, and elodea in 400mM NaCl. We concluded that freshwater was hypotonic (net movement of solution into the cell indicated by arrows), 150 mM NaCl was Isotonic (net movement close to 0, equal number of arrows going in and out), and 400 mM NaCl was hypertonic (net movement of solution out of the cell). We inferred that there was some type of protein receptor or channel that controlled the intake and overall flow of water between the inside and outside of the molecule. Results: As we observed the blood cells in 150 mM NaCl we noticed a high movement of cells, mostly disc-shaped cells, but a few cells that appeared to be sort of star-shaped. Interpretation: Considering the blood cells have maintained their original shape we can infer that the 150 mM NaCl solution is Isotonic in relation to the concentration of the erythrocyte.

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MCB181L When observing the erythrocyte in 400 mM NaCl there was less movement of cells and more star- shaped cells than disc-shaped. Interpretation: The warped star shape of the erythrocytes would prove that the 400 mM NaCl solution is hypertonic compared to the concentration within the erythrocytes. The water within the erythrocyte travels outward by the process of osmosis toward the solution causing the cell to shrivel up into its star formation. Collecting data for the erythrocytes in freshwater was by far the most difficult. It took us a significant amount of time to spot what looks like remains of a cell membrane. We observed small sites of “exploded cells.” Interpretation: After finding these exploded cell sites, we can conclude that the freshwater was highly hypotonic compared to the inside of the cell. This caused the net movement of water to flow inward into the cell and ultimately caused the cell to burst.

MCB181L Freshwater 400mM NaCl 150mM NaCl Overall Observation: The Xenopus Oocyte did not change in shape throughout the different solutions. The color slightly shifted however the cell itself is multicolored so the shift in color could be due to the different perspective of the cell. Interpretation: Considering the cell did not ever change in size we can infer that there was no diffusion or osmosis happening between the cell and the solution. Xenopus Oocytes could potentially be deficient in a protein channel or receptor that regulates passages of liquid through the membrane. Published Data: Figure one shows the relationship between purified 28kDa protein and isolated erythrocyte membranes using immunoblotting. The purified 28kDa protein is found in the same region as the isolated erythrocyte membrane which proves a correlation. We can interpret that the antibody is bound to the protein. In our lab, we investigated the relationship between erythrocytes and different solutions. It was apparent that osmosis or diffusion occur when we place the erythrocyte into various solutions, so this could possibly be regulated by the 28kDa protein. Panel A: Shows the change in oocyte volume over time after moving to a

MCB181L hypotonic solution. The oocytes injected with 28kDa significantly increased in volume when placed in a hypotonic solution. The control buffer oocytes did not increase in volume. Panel b: Displays microscopic images of oocytes at different time points. The membrane in the experimental oocytes erupted however the control oocytes did not. We can interpret that the 28kDa protein changed the behavior of the oocyte making the cell intake the hypotonic solution around it. While there was no intake of liquid within the control cells. This concept of protein behavior can relate to our observations. The erythrocytes in freshwater exhibit similar behavior to the 28kDa oocytes while the Xenopus oocytes in all solutions exhibit behavior shown in the control group of panel b. Revised Model: Model Explanation and Reflection: Explanation: I Throughout the past few labs, we have been exploring the behavior of the cell membrane and its processes of osmosis and diffusion. In our second lab, we explored the elodea leaf plant. We concluded that while the elodea was placed in a hypertonic solution, water would move out of the elodea cell causing the cell to shrink. On the flip side in a hypotonic solution water would move into the cell causing the elodea cell to swell. In the 3 rd lab, we explored the Erythrocytes which are red blood cells. When those are exposed to a hypertonic solution, water leaves the erythrocytes causing them to shrink and warp into a star shape. Inversely, in a hypotonic solution water enters the cell causing them to swell and potentially burst. When drawing models for these two labs we predicted some type of protein channel or receptor that regulated the overall flow of solution inside and outside of the cell. In the 3 rd lab, we also observed the Xenopus Oocyte which did not change in size when placed in different solutions. We concluded that the Oocyte was deficient in the “channel or receptor” present within the elodea and erythrocyte. After experimenting with the 3 types of cells we were given different figures of data pertaining to the concepts we were applying in our experiments. It explored data with oocytes having an experimental group with a protein (28kDa) and a control group with no protein. The oocytes with no protein had zero effects in a hypotonic solution while the

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MCB181L experimental group with the protein increased in size and burst. The experimental data can explain the change in shape and size of the elodea and erythrocytes as they must contain a protein like the 28kDa. The control group data aligned with our results of the oocytes in various solutions. Reflection: Our initial predictions were correct and backed up with future data. Our final model has the same descriptions and principles as our first model however it is a bit more detailed. Our overall understanding of the protein membrane has increased throughout these continuous labs. Scoring Rubric for Membrane Transport Unit Write-Up Section Comments Initial Observations (5 pts) - Elodea data are presented (1 pt), described (2 pts), and interpreted (2 pts) for all 3 conditions. Initial Model (5 pts) - Initial model drawing is included. (3 pts) - Model is described and seeks to explain the phenomenon. (2 pts) Results (10 pts) - Erythrocytes and oocytes data are presented (2 pts), described (4 pts), and interpreted (4 pts) for all 3 conditions. Published Data (5 pts) - Figures 1 & 2 are presented (1 pt), described (2 pts), and interpreted. (2 pts) Revised Model (5 pts) - Final model drawing is included. (5 pts) Model Explanation & Reflection (15 pts)

MCB181L - An explanation of the phenomenon is proposed. (5 pts) - All relevant data is discussed that was used to make the explanation. (5 pts) - Revised model is compared to the old model. (3 pts) - Why changes were made/what was learned is discussed. (2 pts)

Melia Cordero- Membrane Transport unit write up

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