Effect of Temperature on Permeability of Cell Membrane
To investigate the effect of variation in temperature on the permeability of cell membranes using fresh beetroot
Aims
In this investigation, you will subject fresh, washed beetroot discs to different temperatures to investigate the effect of temperature on the permeability of the plasma membrane.
Overview
The beetroot discs will be placed in distilled water at different temperatures. You will compare the intensity of the beetroot pigment that has leaked out from the cells subjectively and possibly objectively using a colorimeter. You can relate the findings to the effect of different temperatures on the permeability of cell membranes in beetroot (as well as in other organisms).
Features of experimental design
The investigation contains these main features of experimental design:
■ There is one independent variable (IV) with a good range. The IV is temperature.
■ The dependent variable (DV) is what is observed or measured as the IV changes. The DV is measured quantitatively and is the amount of beetroot pigment that leaks from the discs.
■ There are many controlled variables (CVs) or constants. They allow a fair test so that we can link the changes in the DV to changes in the IV more reliably.
■ There will be replication through three trials at each value of the IV.
■ There is a control in order to check that the procedure itself does not generate pigment. Not all factors can be controlled, especially the biological material (a confounding variable).
Background information
Fresh beetroot tissue is used in this experiment because it contains a dark red pigment within the vacuole of its cells. The dark red pigment is betacyanin. There is also a yellow pigment called betaxanthin in the vacuole. The pigments are retained in the vacuole by a selectively permeable membrane called the tonoplast. It has a similar fluid-mosaic structure to that of the plasma membrane with protein molecules embedded in a phospholipid bilayer. If these two membranes are
Aims
In this investigation, you will subject fresh, washed beetroot discs to different temperatures to investigate the effect of temperature on the permeability of the plasma membrane.
Overview
The beetroot discs will be placed in distilled water at different temperatures. You will compare the intensity of the beetroot pigment that has leaked out from the cells subjectively and possibly objectively using a colorimeter. You can relate the findings to the effect of different temperatures on the permeability of cell membranes in beetroot (as well as in other organisms).
Features of experimental design
The investigation contains these main features of experimental design:
■ There is one independent variable (IV) with a good range. The IV is temperature.
■ The dependent variable (DV) is what is observed or measured as the IV changes. The DV is measured quantitatively and is the amount of beetroot pigment that leaks from the discs.
■ There are many controlled variables (CVs) or constants. They allow a fair test so that we can link the changes in the DV to changes in the IV more reliably.
■ There will be replication through three trials at each value of the IV.
■ There is a control in order to check that the procedure itself does not generate pigment. Not all factors can be controlled, especially the biological material (a confounding variable).
Background information
Fresh beetroot tissue is used in this experiment because it contains a dark red pigment within the vacuole of its cells. The dark red pigment is betacyanin. There is also a yellow pigment called betaxanthin in the vacuole. The pigments are retained in the vacuole by a selectively permeable membrane called the tonoplast. It has a similar fluid-mosaic structure to that of the plasma membrane with protein molecules embedded in a phospholipid bilayer. If these two membranes are