Practical - the effect of osmosis on plant tissue

• Substances must move into and out of cells for an organism to function.
• Three processes contribute to this movement – diffusion, osmosis and active transport.
• Diffusion is the process of mixing particles.
• Osmosis is the movement of water molecules across a selectively permeable membrane from a region of higher water concentration to a region of lower water concentration.
• Active transport is the process where substances move against their concentration gradient.
• The effect of osmosis on plant tissue can be investigated practically.
• Scientists investigate the effects of osmosis close osmosis.
• The higher the concentration, the more particles of the substance are present.
• The concentration of a solution tells us how much of a substance is dissolved in water.
• Changes in cylinders or discs of fresh potato or beetroot can be measured due to the effect of osmosis.
• Cylinders will have a larger mass than discs, so scientists will have larger measurements to work with.
• Sucrose is a disaccharide made from glucose and fructose and is used as table sugar.
• The experiment could also be carried out using salt – sodium chloride solution – instead of sucrose.
• The aim of the experiment is to investigate the effect of a range of sucrose solutions on the mass of potato cylinders.
• The concentration of the cell sap of potato cells is determined in the experiment.
• The cell sap of plant cells consists of water with dissolved sugars, salts and amino acids.
• in beetroot because the cell sap is red.
• The range for a sucrose solution can be from 0.2 mol dm -3 to 1.0 mol dm -3 .
• Care must be taken when using the scalpel.
• This allows you to make the experiment more repeatable – not all potato cylinders might behave in the same way.
• Set up one containing distilled water.
• It is easy to see the process of plasmolysis close plasmolysed Description of a plant cell in which the vacuole has shrunk and the membrane has pulled away from the wall due to water loss by osmosis
• The molar concentration of a solution is the amount of substance per dm 3 of a solution, or one mole per litre of solution.
• Wear eye protection when using chemical solutions.
• Set up a series of boiling tubes with each of these solutions.
• Carry out the investigation.
• The concentration of sucrose in distilled water is 0.0 mol dm -3 and will act as the control in the experiment.
• Making a series of repeat experiments means that any anomalous results close anomalous result A result that is very different from the rest of the results
• For each sucrose concentration, repeat the investigation for several potato cylinders.
• Make sure when weighing the potato cylinders, that their masses are not mixed up when recording them.
• The effects on plant tissues at a cellular level can be observed using a microscope .
• Prepare a blank results table before you begin.
• Another way of looking at osmosis in plant cells is to mount a piece of onion skin, or beetroot on microscope slides in drops of different concentrations of sugar or salt.
• This experiment shows the effect of osmosis on plant tissue.
• Make sure each tube is labelled with the concentration.
• A 1.0 mol dm -3 solution of a substance contains one mole close mole The amount of substance that contains the same number of particles as there are atoms in 12 g of carbon-12 (contains the Avogadro's constant 6.0 ×10²³ number of particles)
• The amount of substance that contains the same number of particles as there are atoms in 12 g of carbon-12 (contains the Avogadro's constant 6.0 ×10²³ number of particles) is referred to as a mole.
• Risks Make sure that the potato is placed on a ceramic tile when using the cork borer – do not cut the potato cylinders towards your hand.
• can be identified and ignored when a mean close mean The mean is calculated by adding all of the data and dividing by the number of items of data
• The cylinders will decrease or increase in mass if they lose or gain water by osmosis.