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AQA A-Level Biology required practical 4: Investigation into the effect of a named variable on the permeability of cell-surface membranes$9.90
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AQA A-Level Biology required practical 4: Investigation into the effect of a named variable on the permeability of cell-surface membranes
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Course
Unit 2 - Cells
Institution
AQA
AQA A-Level Biology practical report with data and citations
required practical 4: Investigation into the effect of a named variable on the permeability of cell-surface membranes
4 The effect of a names variable on the permeability of the cell
membrane
The effect of alcohol concentration on the leakage of pigment from beetroot cells.
The cell membrane on the surface of a cell is made of several biological molecules
alongside the phospholipid bilayer, including proteins, carbohydrates and cholesterol. The
phospholipid bilayer causes the cell membrane to be selectively permeable which can be
affected depending on variables such as temperature and the concentration of solvents e.g
ethanol. In this experiment, permeability of a membrane is measured with beetroot cells
which contain betalain (a purple pigment). This means that at a higher permeability there will
be more betalain leakage, allowing us to measure permeability via a colorimeter.
The aim of this experiment is to investigate the effect of alcohol concentration on the
permeability of the cell membrane using beetroot cells.
IV: Alcohol concentration
DV: Leakage of pigment/permeability
Control variables and how they were controlled:
Temperature (can affect membrane permeability so needs to be controlled using a water
bath and measured regularly with a thermometer)
Volume of alcohol (measure the volume using a 5cm² syringe)
size of beetroot (need to be as close to the same size as possible-easier and more accurate
comparison- use a ruler when curing them with a scalpel)
Safety/precaution: Goggles, gloves, caution using scalpel and glass equipment and
hot/scalding water.
Results:
Label 0 2 4 6 8 10
Volume of 0 20 40 60 80 100
beetroot/
cm²
Volume of 100 80 60 40 20 0
water/cm²
%Concentratio 0 20 40 60 80 100
n of extract
Absorbance/ 0 0.37 0.63 0.95 1.30 1.97
colorimeter
What is meant by subjective results and quantitative results and what equipment is
required to gather these results?: Subjective results are based upon opinion and are often
biased. Quantitative results focuses on counting and classifying features using numerical
data and constructing statistical models and figures to explain what is observed, equipment
that allows you to gather measurements would be used.
Experiment
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