Aim: The aim of this experiment is to investigate the movement of water into and out of plant cells by osmosis. The cells chosen for study will be taken from potato tubes as they provide a ready supply of homogeneous material.
I did the investigation in two parts, the first part of my investigation was my preliminary investigation and then I did my official investigation. In both of my investigations there are several similarities, such as fair testing, variables, key variables, reliability of evidence and safety precautions. In both of my investigation there were obviously some differences which were in the method, apparatus, results and means of measuring etc.
Essential Background Reading
Osmosis is the diffusion of water molecules across a partially permeable membrane from a high concentration of water to a low concentration of water.
Movement of substances takes place through the cell membrane, which separates the different substances in the cell from its surroundings. This type of membrane allows small molecules such as water to pass through it, but it denies entry to large particles to pass. This membrane is called a partially permeable membrane. The amount of water inside a cell is called water potential.
Turgor is the name given when osmosis takes place between the cytoplasm and the solution outside the cell. This happens when a plant cell is placed in a high concentrated solution of water, water then passes through the cell wall, the cell membrane, and the cytoplasm and into the vacuole. The increased pressure of water inside the vacuole is called Turgor pressure. Then the cell becomes turgid.
Plasmolysis is the opposite of turgor. This happens when plant cells may be placed in a less concentrated solution of water, although this is very unlikely to happen in nature. Water passes out of the vacuole, the cytoplasm, the cell membrane and the cell wall and into the solution outside the cell. The pressure of the vacuole on the cytoplasm decreases until the cytoplasm pulls away from the cell wall.
Diagrams
I have illustrated the diagrams of turgor and Plasmolysis on a separate page.
Fair Testing
This is when the result is only related to the variable being tested.
For e.g. if there are six variables, five variables must be kept identically the same and only one is changed/tested to see how this affects the outcome. This is ensuring that this investigation shall only be testing one variable (Key Variable).
This cell membrane plays an important part in Diffusion. Cell membrane and Diffusion Diffusion is the movement of the molecules of gas or liquids from a higher concentrated region to a lower concentration through the partially permeable cell membrane along a concentraion gradient. This explanation is in the diagram shown below: [IMAGE] Turgor When a plant cell is placed in a dilute solution or a less concentrated solution then the water particles pass through the partially permeable membrane and fill the cell up with water. The cell then becomes Turgor or hard. An example of this is a strong well-watered plant.
If the concentration of one side of the membrane is greater than the molecules will travel from the higher to lower concentration. Eventually there will be a dynamic equilibrium and there will be no net movement of molecules from one side to the other. Osmosis is the diffusion of water. Like diffusion, the water moves from a region of higher water potential to a region of lower water potential.
If a plant cell is places in a hypotonic solution the cell has a lower water concentration to that of the solution. Water will move into the cell by osmosis from a high water concentration outside the cell to a lower water concentration inside the cell through a selectively permeable membrane. The cell becomes turbid
Osmosis in Carrots Background Osmosis is the diffusion of water from a dilute solution to a more concentrated solution through a partially permeable membrane, which allows the pass of water molecules but not solute molecules. [IMAGE][IMAGE][IMAGE][IMAGE][IMAGE][IMAGE][IMAGE][IMAGE]If a cell is placed in a less concentrated solution water enters because the less concentrated solution will have a high concentration of water than the inside of the cell. Once the cell takes in maximum water the cell becomes turgid. If the cell was to be placed in a high concentrated solution, water would leave the cell because the cell would contain a low concentrated solution. So in the low concentrated solution there will be a high concentration of water and in the high concentrated solution there will be a low concentration of water.
there would be no flow of water into or out of the cell so the cell
Most cell membranes are like that, being permeable to water and some solutes only. Osmosis is therefore the diffusion of water through a partially permeable membrane. The basic principles of diffusion apply here.
Activity 3: Investigating Osmosis and Diffusion Through Nonliving Membranes. In this activity, through the use of dialysis sacs and varying concentrations of solutions, the movement of water and solutes will be observed through a semipermeable membrane. The gradients at which the solutes NaCl and glucose diffuse is unproportional to any other molecule, therefore they will proceed down their own gradients. However, the same is not true for water, whose concentration gradient is affected by solute ...
== = This experiment is based on the concept of Osmosis. Osmosis is the diffusion of water molecules from a region of high water concentration to a low water concentration through a semi permeable membrane (in this case, the cell potato cell membrane). The cell walls of the potato cells are semi permeable meaning that water molecules (which are small) can fit through but other bigger molecules such as glucose cannot pass through. The water molecules can flow both ways through the membrane, letting molecules both in and out.
Diffusion is when any molecule moves from high to low concentration. Molecules will spread until they have equilibrium. Diffusion equilibrium is reached when the concentration gradient reaches zero. In the lab that we did in class was diffusion. We used iodine and starch. We put starch in the plastic tube and tied it making sure there was no starch on the edges. Then we put iodine in the water and put the starch in the iodine. We kept it for a while. The iodine went in the starch making the water clear and the starch to turn from white to dark brown. This shows diffusion because it shows how the iodine went from high concentration to low concentration. A real life example of diffusion is when you spray perfume in one corner of a room, the molecules of the spray will move around the room. That’s
Osmosis is the movement of water molecules from a dilute solution (has a High Water Potential) to a more concentrated. solution (has a Low Water Potential) through a selectively permeable. membrane in order to achieve equilibrium. A membrane that allows water. to pass through, but not solute molecules.
The purpose of this lab was to see firsthand the diffusion of a substance across a selectively permeable membrane. Diffusion is the movement of molecules from an area of high concentration to an area of lower concentration until both concentrations are equal, or as you could more professionally call it, equilibrium. This concept is one that we have been studying in depth currently in Biology class.
The overall purpose of the experiments in this lab was to introduce the function and structure of the plasma membrane, describe the workings of diffusion and osmosis, and to demonstrate how different factors such as particle size, temperature, and space of diffusion area affect the rate of diffusion. With the results from the experiments, it can be concluded that all of the factors listed do affect diffusion, and there may be many more than are unaccounted for.
Transpiration is the loss of water vapour from the leaves of plants; a process that begins when water is carried from the roots of a plant to small pores on the underside of leaves, where the majority of it is changed to water vapour and released into the atmosphere (United States Geological Survey (USGS), 2014). Transpiration has three major roles in the life of a plant. The first is to transport water and other essential minerals around the plant. Plants use xylem vessels, which are vertically elongated vessels with lignified walls, to transport water and dissolved minerals from the roots to the leaves, where they can be used for photosynthesis and cell growth (Roberts, King, 1987). Phloem vessels transport carbohydrates, created during photosynthesis, from the leaves to the rest of the plant to be used in growth (Whiting, 2010). Plants also use transpiration as an evaporative cooling system. This is possible because the process of evaporation is an endothermic reaction; it requires energy to break the hydrogen bonds between liquid water molecules, changing them to free water molecules, or, water vapour. This energy is taken from the leaf in the form of heat, which, in turn, cools the plant (Plant and Soil Sciences, 2014). Transpiration also helps to keep the plant stiff and upright. As water leaves the plant, via evaporation, more is brought up through the roots, maintaining a constant amount of water in the plant pushing against the cell walls; this is known as turgor pressure (Whiting, 2010).
Osmosis is the passage of water molecules from a weaker solution to a stronger solution through a partially permeable membrane. A partially permeable membrane only allows small molecules to pass through, so the larger molecules remain in the solution they originated in. Solute molecule [IMAGE] [IMAGE] Water molecule [IMAGE] The water molecules move into the more concentrated solution. When water enters a plant cell it swells up. The water pushes against the cell wall and the cell eventually contains all that it can hold.
When plants such as seaweeds or others that grow under water, their parts are supported on all sides by hydrostatic pressure. There is not much difference in the density between plant cells and their surrounding liquid environment. Aquatic plants do not require significant structural support; their cell walls only contain polysaccharides, c...