Tissue from an onion is a good first exercise in using he microscope and viewing plant cells. The cells are easily visible under a microscope and the preparation of a thin section is straight forward. An onion is made of layers, each separated by a thin skin or membrane. In this exercise you will make a wet mount on a microscope slide and look at the cells of the onion membrane magnified by the high power, compound microscope. We also can observe the actual structure of plant cells which consists of nucleus, vacuole, cytoplasm, cell wall etc.
This experiment indicates the transport across membrane in plant cells when involving water through osmosis. Materials and methods : Materials I Apparatus I Onion Distilled waterfall sugar/sucrose I Small knife Glass slipcover oscilloscope Filter paramagnetic stirrer/stirring arthropods Beakers (250 ml & 500 mi) I l. Scale off carefully the epidermal layer of an onion and place it on a drop of distilled water on the glass slide. II. Lower down the glass cover slowly on the epidermal layer using the needle. Ill. Examine the onion cells through the microscope. IV.
Draw the structure of the onion cells as observed under microscope. V. Remove the distilled water using filter paper. VI. Place a drop of 5% (w/v) sucrose solution at a side of the cover slip and draw the solution across the epidermal layer by placing filter paper on the other side of cover slip. VII. Examine the onion cells once again through the microscope. Draw the structure of the onion cells as observed under microscope. VIII. Repeat step (v – vii) using 30% (w/v) sucrose solution. IX. Compare the structure of onion cells in solutions at different concentrations.
Experiment Transport Across Membrane Lab Report Matriculation
Results : The onion cells in distilled water under microscope I The onion cells in 5% (w/v) sucrose solution under microscope I The onion cells in 30% (w/v) sucrose solution under microscope I Discussion : In this experiment we had done 3 different solutions to see the effects of these solutions with plant cells (onion cells). For hypotonic solution (distilled water), because of the different pressure water moves into the cell by osmosis is faster or we can also say pressure potential is higher. Thus it caused the cell to swell without bursting due to the presence of cell wall.
The increased pressure pushes the cytoplasm against the cell wall and the cell becomes turgid. For isotonic elution (5% (w/v) sucrose solution), water moves in and out of the cell at the same rate hence there is no net movement of water. In the other term solute potential is equal to pressure potential. The cell retains its shape. On the other hand, for hypersonic solution (30% (w/v) sucrose solution), water moves out from the cell by osmosis, the cytoplasm pulls away from the cell wall and the cell becomes flaccid.
Its the same as solute potential is higher in other terms. In this situation, the cell is said to be polymerase. Experiment 2 : The purpose of doing this experiment is to determine the effects of isotonic, hypotonic, and hypersonic solutions to potato cells. From a brief opinion we can conclude the hypothesis ; the concentration of an external solution which is isotonic to the cell sap does not affect the size, shape and mass of the potato strips. Particularly in this experiment we have to use a specific formula to calculate percentage change in the mass of potato strips.
Given formula : Percentage change = Final mass – Initial mass x 100 Initial mass This is because, the easiest way to observe the changes occur to the potato strips was to weigh the initial mass and its final mass after being put into the three illusions. Material and methods : Potato Table salt/Inaccessibility water Small knife Penchant digital balanced Vials Beakers (250 ml & 500 ml )Magnetic stirrer/stirring radiation I l. Slice your potato into sticks that 4-6 CM long and 1 CM diameter. Record their initial weight (g) in 2 decimal places, e. G: 3. 15 g. II.
Prepare 4 vials with different salt solutions: 10% (w/v) Nasal, 3. 5% (w/v) Nasal, 0. 88% (w/v) Nasal, and distilled water. Ill. Put one potato stick into each solution. Record the weight of the potato sticks again after 20 min. Calculate the change in weight: final wet. Initial wet. IV. Calculate the percentage of water gain or loss as follow: V. % weight change = Final Wet- Initial Wet x 100 Initial Wet Salt concentration I Initial weight of potato stick (g) I Final weight of potato stick (g) I Change in weight (g) Change in weight (%) I Rank relative Water loss or gain | Nasal | 0. 88 | 0. 76 | -0. 12 13. 6 Loss 3. % Nasal | 0. 88 | 0. 83 | -0. 05 5. 68 Loss 0. 88% Ana | 0. 88 0. 88 +0. 00 | 0. 00 | No change I Distilled Water | 0. 88 | 0. 97 | +0. 09 | 10. 2 | Gain I The data table for long stick potato gain | Niacin | 0. 28 | 0. 26 | -0. 02 7. 14 | 3. % Nasal | 0. 28 | 0. 24 | -0. 04 14. 3 Loss I 0. 88% Nasal | 0. 28 0. 28 +0. 00 | 0. 00 | No change I Distilled Water | 0. 28 | 0. 36 | +0. 08 | 28. 6 | Gain I The data table for short stick potato In this experiment , potato cells were put into four different solution concentrations which are distilled water, 10% (w/v), 3% (w/v) and 0. 88% (w/v) of sodium chloride.
The concentration of the external solution (0. 88% (w/v) sodium chloride) which is isotonic to the cell sap of the potato cell will not produce any percentage change in the mass of the potato. The water moves in and out of the ell at the same rate and the potato strip remains turgid. We can also conclude that the solute potential is equal to pressure potential. In distilled water, the potato strips become longer and increased in mass. The potato strips are hypotonic when immersed in distilled water. The rate water moves into the cells are faster then water moves out thus the pressure potential is higher.
In solution with the concentration of 3. 5% (w/v) and 10% (w/v) of sodium chloride, the potato cells become smaller and least in mass. The potato strips are hypersonic when immersed in these concentrations. The rate of water that eves out from the cells are faster then rate of water that moves into the cells hence the solute potential is higher. Experiment 3 : The osmotic gradient is the difference in concentration between two solutions on either side of a comparable membrane, and is used to tell the difference in percentages of the concentration of a specific particle dissolved in a solution.
Usually the osmotic gradient is used while comparing solutions that have a comparable membrane between them allowing water to diffuse between the two solutions, toward the hypersonic solution (the solution with the higher concentration). Eventually, the force of the column of water on the hypersonic side of the comparable membrane will equal the force of diffusion on the hypotonic (the side with a lesser concentration) side, creating equilibrium.
When equilibrium is reached, water continues to flow, but it flows both ways in equal amounts as well as force, therefore stabilizing the solution. Osmosis is the diffusion of molecules from where they are abundant to where they are scarce through a semi permeable membrane. In red blood cells, this semi permeable membrane is the cell membrane. If red blood cells were placed in a solution abundant with water molecules, they would diffuse into the cells through the membrane Materials and Methods : Distilled water 4. 0% (w/v) Nasal 0. 5% (w/v) Niacin I Glass slide Cover slip Microscope Test tubes Cotton Lancet Beakers (250 ml & 500 ml) Magnetic stirrer/stirring rod Spatula I i. Label test tubes with A, B, and C. Ii. Fill the test tube A, B, and C with 5 ml of distilled water, 4. 0 % (w/v) Nasal and 0. 85% (w/v) Nasal, respectively. Iii. Add a drop of blood into each test tube and left them for 5 min. Iv. Examine a drop of each solution under microscope. The red blood cells in distilled water under microscope I The red blood cells in 4. 0% (w/v) Niacin solution under microscope I The red blood cells in 0. 5% (w/v) Nasal solution under microscope I When the osmotic pressure of the solution outside the blood cells in higher than the osmotic pressure inside the red blood cells, the solution is hypersonic. The water inside the blood cells exits the cells in an attempt to equalize the osmotic pressure, causing the cells to shrink. When the osmotic pressure outside the red blood cells is the same as the pressure inside the cells, the solution is isotonic with respect to the cytoplasm. This is the USUal condition of red blood cells in plasma. The cells are normal.