Cell Membrane Permeability

The cell membrane has a wide range of functions beyond separating the cell from its external environment.

Identify the functions of a plant cell membrane from the list below. You can select more than one.

• It receives signals and transmits these to the inside of the cell

• It regulates the entry and exit of substances into and out of the cell

• It can contain enzymes that digest substrates

• It supports the cell and prevents lysis (bursting) if there is a net gain of water by osmosis

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NGSS.HS-LS1-3

Solution A has a concentration of 2.500 × 10^-³ g dm^-³.

The instructions below explain how to prepare a range of further solutions.

*solution B – add 10 cm³ of distilled water to 10 cm³ of solution A

*solution C – add 5 cm³ of distilled water to 5 cm³ of solution B

*solution D – add 9 cm³ of distilled water to 1 cm³ of solution A

*solution E – add 9 cm³ of distilled water to 1 cm³ of solution C

Select the correct statements from the list below. You can select more than one.

• Using the method of proportional dilution, solution B has a concentration of 1.250 × 10^-3 g dm

• Using the method of proportional dilution, solution C has a concentration of 6.125 × 10^-4 g dm^-³

• Using the method of serial dilution, solution E has a concentration of 1.250 × 10^-4 g dm^-3

• Using the method of proportional dilution, solution D has a concentration of 6.125 × 10^-4 g dm^-3

In the investigation you carried out, a colorimeter was used to measure the absorbance of the red solution following the incubation of beetroot cylinders in distilled water.

Select the correct statement.

• The absorbance of red light is measured because red light is reflected most effectively by the red solution

• The absorbance of green light is measured because green light is reflected most effectively by the red solution

• The absorbance of red light is measured because red light is absorbed most effectively by the red solution

• The absorbance of green light is measured because green light is absorbed most effectively by the red solution

Select all of the variables in the list below that should be standardised in the experiment that you carried out.

• Mass and surface area of beetroot cylinders

• Absorbance of the solution

• Beetroot from which cylinders were extracted

• Volume of water

• Time for incubation

When beetroot tissue is placed into water at a temperature of more than 60°C, a high concentration of red-purple pigments called betalains diffuse into the surrounding water.

Select the statement(s) that explain why the same effect is not seen when beetroot tissue is placed in water at room temperature. You can select more than one reason.

• Betalain molecules are insoluble in water

• Betalain molecules cannot be converted into colourless compounds because the enzymes that do this have been denatured

• Betalain molecules are polar

• Betalain molecules are large, relative to the size of phospholipid molecules

In an investigation into the permeability of plant cell membranes, a student incubated six cylinders of beetroot tissue in different concentrations of ethanol. After a period of incubation, the absorbance of the solutions was measured using a colorimeter.

Select the statement(s) below that best describe how the graph of the data from the above experiment should be drawn. You can select more than one

• The points should be plotted as a bar chart

• The points should be plotted as a line graph

• The ethanol concentration should be on the y-axis of the graph

• When the points are plotted, the line that joins them together should be extrapolated from 15% to 0% ethanol concentration (back to the origin).

• A linear scale should be used on both axes