Learn: Core Practical 3 - Membrane Permeability

Welcome!You've already learned about cell membranes, diffusion, osmosis, and the fluid mosaic model. Now, let's build on that knowledge and investigate how alcohol concentration or temperature affects membrane permeability.

What is Membrane Permeability?Membrane permeability refers to how easily substances can pass through a cell membrane. This depends on factors like temperature, the presence of chemicals (e.g., alcohol), and the membrane's structure.

Why Study Membrane Permeability?Changes in permeability can affect how cells function, as they rely on regulated exchange of substances. For example, damage to membranes can cause leakage of vital molecules, like proteins or ions.

Factors That Affect Membrane PermeabilityTwo key factors are temperature and alcohol concentration. High temperaturesalcohol

Core Practical OverviewIn this investigation, you will test how different concentrations of alcohol or changes in temperature affect membrane permeability in beetroot cells. The pigment betalain, stored in vacuoles, will leak out of the cells through damaged membranes, allowing us to measure permeability.

Key Materials and EquipmentYou'll need beetroot, distilled water, alcohol solutions of varying concentrations (e.g., 10%, 20%, 30%), a colorimeter, test tubes, and a scalpel to prepare beetroot slices.

Steps for the PracticalFollow these steps to investigate membrane permeability:Prepare equal-sized beetroot slices using a scalpel.Rinse slices to remove excess pigment.Place slices into test tubes containing different alcohol concentrations or water at varying temperatures.Incubate for a set time (e.g., 30 minutes).Use a colorimeter to measure pigment concentration in the solution.

How Does a Colorimeter Work?A colorimeter measures the absorbance of light by a solution. The higher the absorbance, the more pigment has leaked out, indicating greater membrane permeability.

Review Time!Great work! You've learned about membrane permeability, the effects of temperature and alcohol, and the steps of the core practical. Now let's test your understanding with a few questions.