Table Two — Chemical Test Results Glucose Blue-colored Glucose Indicator Solution Amber-colored Starch Indicator Solution What test would you need to perform to prove that it is the combination of glucose and the Glucose Indicator Solution that changes color when heated and not just the glucose or the Glucose Indicator Solution alone? What do you think would happen if you watered your houseplants with salt water? The bag was filled with 5. The observation under the microscope of a cell of an onion skin soaked for 15 minutes in distilled water showed that the cell membrane was pressed against the cell wall. As a result your blood may become more viscous but I don't believe anything would happen the the red blood cells specifically. Your teacher will provide a small, curved section of an onion for you to use. Record your prediction here: 10. Popcorn sold at most movie theaters is very salty, causing people to become thirsty and buy soft drinks.
Carefully remove the outer layer of cells. Explain why or why not. Osmosis in Red Onion Cells By: Youssef Gharib Brief Description of Osmosis in Red Onion cells: Osmosis is the diffusion of water from an area of low concentration to an area of high concentration across a semi-permeable membrane. In salt water, the concentration of water outside is either less than concentration of the water in the cells, so the water loss would occur passively, without the need for the vacuole. In other words, equal numbers of water molecules move into and out of the cell. Question: How will the vacuole inside the cells of the outer membrane of a red onion react when deionized water, a 1%, and a 10% saline solution are added to the cells? Specifically, it is the diffusion of water across a membrane. Microscope - while collecting data, and observing what happens to the red onion, the same microscope shall be used for observing what happens to the vacuoles.
Record qualitative and quantitative observations again on the change in size of the onion cell vacuole. You can calculate the percentage of plasmolysed cells and plot a graph of percentage plasmolysis against sodium chloride concentration. We call the liquid with more dissolved solutes in it a hypertonic solution and the liquid with less dissoved solutes is called a hypotonic solution. In general, these membranes are impermeable to organic solutes with larege molecules, such as polysaccharides, while permeable to water and small, uncharged soluts. Label the cell wall, cell membrane, and cytoplasm. Peel off the white tissue and you should get a thin line of intact red cells on the fold line. It is a semipermeable membrane, which means that some particles pass through the membrane easily while others cannot.
You will need to keep them for review before the Regents Examination. Based on your observations, draw and color a typical red onion cell mounted in salt solution. The observation showed a large number of onion cells. Replace it with distilled water added at the other side of the coverslip. Take a dropper and add several drops of salt solution to one side of your cover slip while placing a small piece of paper towel along the opposite edge of the cover slip. If the plant finds itself in a hypertonic solution, water will rush out of the cells causing the cells to shrivel up.
Step four was repeated, then five drops of 10% saline solution were dropped onto the slide. Carefully add a coverslip and examine the. Have your teacher observe your slide with the microscope to be sure you have a good preparation. The structure of one onion cell had a general rectangular shape with a developed cell wall, which gives the rectangular shape to the cell and a cell membrane just beneath it. You can do this by placing a small piece of paper towel against one edge of the cover slip and adding several drops of the salt solution to the other side. Osmosis is defined as the diffusion of water solvent from areas of high solvent more amount of water concentration to areas of low solvent less amount of water concentration across a semi-permeable membrane. Remove the paper towel before it soaks up too much liquid and dries out the slide.
During part 1 of this laboratory activity, one group of students followed the directions incorrectly. The red blood cells will absorb water and increase in size. Explain why some substances were able to pass through the membrane while others were not able to. Teaching notes This experiment could be run as a qualitative investigation of the effects of water and sodium chloride solution on the contents of plant cells. Hypothesis: If a saline solution is added to the outer membrane of a red onion cell, then based on the amount of the solution, it will cause the vacuole inside the cell to become hypertonic thus shrinking in size.
Take care with microscope slides and especially cover slips which are fragile and break easily. The cell swelled because of the increased amount of distilled water but the cell wall kept the same rectangular shape. Have your teacher check your slide with the microscope to be sure you are able to observe the effects of salt on cells. Describe what happens to the water content of the red onion cells when they are placed in a salt solution. Remember that this membrane is only model. Cells are plasmolysed plasmolysis has occurred when the cell contents shrink and come away from the cell wall.
Problem: How do solutions of various salt concentrations influence osmosis in relation to an onion cell? You should see a change in the cells from your previous observation. If the water molecules are diffusing into the cell through the selectively permeable membrane the cell will become turgid. Clean and dry slide and coverslip. Two diagrams of osmosis are shown in figures 1 and 2. Which represents cells in pure water? Materials: per student group : red onion epidermis forceps, dropper distilled water NaCl solution paper towels microscope slide cover slip Procedure 1. A small square of a red onion skin membrane was observed under a microscope at high power X40 magnification. Make a properly labeled, careful drawing of the cells' appearance.
Results Figure 1 The Change in Mass g of Osmosis Bags Over Time When Subjected to Various Conditions Bag 1 represents the control. The goal is to make that end completely leak-proof. To prevent the cells from bursting lysis , plant cells are surrounded by a hard cell wall. Suppose you were trapped on a desert island with no sources of fresh water. The observation under the microscope of a cell of an onion skin soaked for 15 minutes in distilled water showed that the cell membrane was pressed against the cell wall. Many fresh-water one-celled organisms have structures called contractile vacuoles.
Overall the results proved the hypothesis correct with major findings being a higher concentration of salt causing a hypotonic environment and a low concentration. Observe the effects of the saline salt solution on the onion cells. When a Red Blood Cell is submersed in a high concentration of saline solution it will create a hypertonic environment and therefore cause the cell to rupture due to the process of osmosis. As abeove, suppose a permeable membrane seperates equal amounts of pure solvent and a solution. A small square of a red onion skin membrane was observed under a microscope at high power X40 magnification. Diffusion is the process by which the collisions between molecules cause them to continually spread apart from each other.