BIOL1001 Lab #6 Osmosis and Diffusion PDF

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Alyssa Fields BIOL1001 Virtual Post-Lab #6: Cellular Transport This lab comes from page 91-99 in your lab manual. Ex 5.3- Procedure 2: Diffusion across a membrane Diffusion takes place when molecules move from an area with a higher concentration to an area with a lower concentration. An example of diffusion occurring is when you peel an orange in the kitchen and the orange scent travels through the air from an area of high concentration (the orange peel in the kitchen) to an area of low concentration. When given enough time and space for the scent to travel, you will smell the diffused orange scent in rooms close to the kitchen, like your office or bedroom. Simulation #1: Permeable Membrane Diffusion https://www.labxchange.org/library/pathway/lx-pathway:c5725a90-4298-4cf5-a2f59b1b719def95/items/lx-pb:c5725a90-4298-4cf5-a2f5-9b1b719def95:lx_simulation:68ff2e15 Simulation Directions: Cell membranes are composed of two layers of phospholipids (bilayer). Some molecules are able to cross a membrane directly, without using assistance from membrane channels or transporters. Oxygen and carbon dioxide are small non-polar molecules capable of freely moving through a cell membrane. But keep in mind that molecules don’t always move in one direction. Instead they attempt to reach equilibrium, an equal concentration of molecules inside and outside of the cell, and molecules may pass several times over a membrane before equilibrium is reached. Click “Start Simulation” and set the model up with high oxygen and low carbon dioxide outside the cell. Then set the model to low oxygen and high carbon dioxide inside the cell. This is similar to the way our human cells behave. We need to get oxygen from the outside air into our cells so they don’t die. Diffusion makes it possible for oxygen to get in. Inside the cells chemical reactions produce carbon dioxide waste. Our cells want to get rid of this garbage inside the cell and diffusion makes it possible. 1) In which direction do the oxygen molecules move initially across the membrane? The oxygen molecules move to the right 2) In which direction do the carbon dioxide molecules move initially across the membrane? The carbon dioxide move to the left 3) True or False: When the levels of carbon dioxide are equal on both sides of the cell, carbon dioxide stops moving across the membrane. False Next try changing the simulation to different levels of oxygen or carbon dioxide on either side of the membrane. Watch the concentration levels change until they are equal inside and out (equilibrium). 1

Permeable Membrane Diffusion: Interactive created by Concord Consortium using Next-Generation Molecular Workbench software, with funding by a grant from Google.org. Copyright © 2021 The Concord Consortium. All rights reserved. The software is licensed under the MIT license. Please see license.md for other software and associated licensing included in this product. Please provide attribution to the Concord Consortium and the URL https://concord.org.

Simulation #2: Semipermeable Membrane Diffusion https://www.labxchange.org/library/pathway/lx-pathway:c5725a90-4298-4cf5-a2f59b1b719def95/items/lx-pb:c5725a90-4298-4cf5-a2f5-9b1b719def95:lx_simulation:381a1f4f Not all molecules are able to move across a cell membrane because the cell membrane is semipermeable. Large molecules and charged ions are unable to enter or exit a cell without assistance. A semipermeable membrane allows these types of substances to pass through it only if there is a membrane pore, channel, transporter, or other gateways through the membrane. Click “Start Simulation”. Leave the set-up the way it is displayed and click the “play” button. Pause the simulation after 10 seconds. 4) How many large green molecules are on the left side of the screen? 10 5) How many large green molecules are on the right side of the screen? None 6) How many small blue molecules are on the left side of the screen? 7 7) How many small blue molecules are on the right side of the screen? 49 Next reset the simulation. This time make the pores larger. Click “play” and allow the simulation to continue for 10 seconds. 8) How many large green molecules are on the left side of the screen? None 9) How many large green molecules are on the right side of the screen? 10 10)How many small blue molecules are on the left side of the screen? 16 2

11)How many small blue molecules are on the right side of the screen? 40 Reset the simulation one more time. This time make the pores tiny. Click “play” and allow the simulation to continue for 10 seconds. 12)How many large green molecules are on the left side of the screen? 10 13)How many large green molecules are on the right side of the screen? None 14)How many small blue molecules are on the left side of the screen? None 15)How many small blue molecules are on the right side of the screen? 56 Semipermeable Membrane Diffusion: Interactive created by Concord Consortium using Next-Generation Molecular Workbench software, with funding by a grant from Google.org. Copyright © 2021 The Concord Consortium. All rights reserved. The software is licensed under the MIT license. Please see license.md for other software and associated licensing included in this product. Please provide attribution to the Concord Consortium and the URL https://concord.org.

Ex 5.4: Osmosis Osmosis occurs when water diffuses across a cell membrane, either entering or exiting the cell. The process of osmosis must be tightly controlled by cells, otherwise they will die. In animal cells too much water inside a cell can cause it to POP! like a water balloon, but too little water inside a cell can cause a cell to shrink up and die. For example: A blood cell has many salts, proteins, and water inside the cell. If you place a red blood cell in water, it will quickly take up water until it bursts. That is why plasma, the liquid portion of our blood, is made of water mixed with proteins and salts. This liquid plasma mixture prevents the unnecessary gain of water by our blood cells, and stops the POP! In plants, osmosis is just as important. Plant cells have an additional cell wall that surrounds the outside of the cell membrane which prevents plant cells from taking on too much water through osmosis. Plant cells don’t POP! like animal cells. However, plants with too little water become wilted and shrunken. This happens when water moves out of the plant cells by osmosis. Without a lot of water inside the plant cells to make them bloated and strong, plant cells deflate and the plant can no longer support itself against the pull of gravity and wilts. However, after watering the plant, the cells will once again swell with water and the plant stands upright. Tonicity of a solution impacts the pressure on a cell, and refers to the concentration of solutes (salt) in the solvent (water). The concentration of salt and water in a solution can cause a cell to gain water, lose

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water, or have no net increase/decrease of water due to osmosis. There are three types of tonic solutions: Hypotonic, Hypertonic, and Isotonic.  Hypotonic: Outside a cell, a hypotonic solution has a lower solute concentration compared to the solution inside the cell. Water then moves into the cell because the inside of the cell is saltier and causes an animal cell to lyse (POP!) or a plant cell to become turgid (tight and bloated).  Hypertonic: Outside a cell, a hypertonic solution contains a higher concentration of solutes compared to the solution inside the cell. Water then moves out of the cell into the saltier water outside of the cell causing an animal cell to shrivel and a plant cell to plasmolyze (underneath the cell wall the cell shrivels inside).  Isotonic: Outside the cell, an isotonic solution has the same solute concentration, the solution inside the cell. Water then moves into and out of the cell at the same rate, causing no net gain or loss of water to the cell.

LadyofHats https://commons.wikimedia.org/ w/index.php?curid=1685492

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Hypertonicity and Hypotonicity of Plant Cells: Lab Book Exercise 5.4 Procedure 2 (page 97 Lab manual) Observe the following video showing the impact of a hypertonic solution (sucrose) onto cells in an elodea leaf. After a few seconds a hypotonic solution of pure water is placed on the cells. https://www.youtube.com/watch?v=zVvHn6Sj9PQ Note: The cells look like little greenish/brownish bricks stacked on each other, the cell walls make a faint gray rectangle on the outside of the cell. Inside the cells you can observe the bright green chloroplasts and cytoplasm (cell liquid). Record you observations: 16) What do the cells look like in the original isotonic solution? The cells look normal as they would look in a pond, all the cells look the same and moving water in and out at the same rate. 17) What do the cells look like in the hypertonic solution? The Cell shriveled and pulled away from the cell wall.

18) What do the cells look like in the hypotonic solution? The cell was pressed against the cell wall and the cell was about to burst.

Osmosis Experiment: Complete the simulated Cell Homeostasis Virtual Lab - Explore: Tug of War(ter). Virtual Experiment: https://www.texasgateway.org/resource/cell-homeostasis-osmosis  Use your post-lab worksheet as your lab notebook to complete this assignment.  Begin by watching the water video in the experiment.  Scroll down on the page and Click “Start” to begin the Experiment  Fill in the table below with the measured numbers from the experiment. The “cell” is considered the dialysis tubing in this experiment.

A: Control

B

C

D

E

Beaker Solution

0% Sugar

0% Sugar

5% Sugar

10% Sugar

15% Sugar

Dialysis Tube “Cell” Solution

0% Sugar

10% Sugar

10% Sugar

10% Sugar

10% Sugar

Initial Mass of Tube “Cell”

17.59

8.75

11.27

10.71

18.05

Final Mass of Tube “Cell”

17.66

10.40

12.10

10.57

15.60

Gain or Loss of Mass (+ or -)

+

+

+

-

-

Solution Outside “Cell”?

Isotonic

Hypotonic

Hypotonic

Isotonic

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Hypertonic

Hypotonic Hypertonic Isotonic

19) If the change in concentration of the sugar solutions in the beakers is the independent variable what was the dependent variable? The amount of time the dialysis tubes were exposed to the sugar solutions in the beakers.

20) Name two variables that were held constant in this experiment? The amount of water in the beakers, and the type of solute (dissolved solid)

21) If you were to plot this data what would you use? A) Line graph B) Bar graph C) Pie Chart D) Skin graph 22) Why was water (0% sugar inside/0% sugar outside) used as a control in this experiment? To let us observe if the treatment has an effects while we do the experiment.

Content Covered in Lab #6 Osmosis and Diffusion This lab comes from page 91-99 in your lab manual. 1. Lab book Exercise 5.3 Diffusion Procedure 1: Simple Diffusion Exercise – simulation Procedure 2: Diffusion across a membrane – simulation 2. Lab Book Exercise 5.4: Osmosis Procedure 1: Observing Osmosis – Virtual Experiment Procedure 2: Hypotonocity and Hypertonocity in Plant cells – Youtube video

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