The Permeability of the Beet Root Membrane
IB Biology SL
Performed: Due:
Foreword
Permeability of a cell to solutes in an aqueous solution depends upon the physical
and chemical make-up of the membrane. The maintenance of the living cell depends
upon the continued presence and functioning of a selectively permeable membrane.
If the nature of the membrane is altered in any way, this may affect it’s permeability
and thus the properties of the cell of which it is a part. Irreversible changes in the
permeability of the membrane usually lead to the death of the cell. In this
experiment, we will study the effects of changes in the environmental conditions on
the permeability of living beet root cells.
Roots of beet (Beta vulgaris ) contain large amounts of a reddish pigment called
betacyanin, localized almost entirely in the large central vacuoles of the cells.
Betacyanin in healthy cells remains inside the vacuoles, surrounded by a vacuolar
membrane called a tonoplast. The entire cell is surrounded by a cellular or plasma
membrane. Environmental stresses can damage the membranes, allowing
betacyanin to leak through the tonoplast and plasma membrane. This leakage of
betacyanin will produce a red colour in the water surrounding the stressed beet.
Thus the degree of membrane damage can be determined by monitoring the
intensity of the colour leakage resulting from a treatment.
Objectives
By the end of this investigation the student should be able to:
1. Describe the effect of temperature on the permeability of beet root tissue.
2. Relate the theory of membrane structure as considered in class, with the
observations made during this activity.
Introduction:
Discuss the structure of the cell membrane as it relates to its permeability. You may
use figures or diagrams if they will aid in illustrating this structure [all figure must
be numbered, titled and referred to in the text of your work]. Include relevant
research information concerning the affect of the experimental treatments on the
permeability of plasma membranes. When refering to facts which are not general
knowledge, use the MLA style to cite the source of the information [ i.e. The cell
membrane consists of protein molecules embedded in a phospholipid bilayer
(Bretscher, 1985)]. There is no word minimum. (4 marks)
