PMT exam questions (2) & answers 2023/2024
1 The cell vacuoles of beetroot (Beta vulgaris) contain the red pigment betalain.
A student investigated the effect of temperature on the permeability of beetroot cell
membranes.
In this investigation, five pieces of beetroot were used. One piece of ...
PMT exam questions (2) & answers
2023/2024
1 The cell vacuoles of beetroot (Beta vulgaris) contain the red pigment betalain.
A student investigated the effect of temperature on the permeability of beetroot cell
membranes.
In this investigation, five pieces of beetroot were used. One piece of beetroot was left in 10 cm3 of
distilled water for 20 minutes at 20 °C.
After 20 minutes, the piece of beetroot was removed and the intensity of the colour of the water was
measured using a colorimeter.
This was repeated with the other pieces of beetroot using water temperatures of 40 °C, 60 °C, 80 °C and
90 °C.
(a) The student's results are shown in the graph below. ) Using the information in the graph, describe the
effect of temperature on the permeability of the cell membranes. - ANSWER-an increase in temperature
increases the permeability / eq ;
2. idea that increase in permeability is non-linear e.g. greatest increase between 40 and 60 oC, less
change up to 40oC ;
3. credit correct manipulation of figures e.g. 4.9 increase between 40 and 60 oC
(ii) Using the information in the graph and your knowledge of membrane structure, explain the effect of
temperature on the cell membranes. - ANSWER-idea that increased kinetic energy increases movement
of molecules ;
2. reference to phospholipids moving / eq ;
3. idea that (membrane) proteins denatured ;
4. idea that there is more {denaturation / disruption / eq} at {higher temperatures / above 40 oC } ;
5. idea that {betalain / pigment} can escape from the {cell / vacuole /eq } when the membrane is
disrupted ;
6. comment on the disruption of the vacuole membrane / eq
*(b) Using all the information given in the question, describe how this investigation could be carried out
to provide valid and reliable results - ANSWER-appropriate standardisation of source of beetroot tissue ;
, 2. standardisation of size of beetroot pieces / eq ;
3. need for {washing / rinsing / eq} {beetroot / eq} (thoroughly) ;
4. use of waterbath (to maintain / change temperature) ;
5. reference to repeats at each temperature / replicates / eq ;
6. se of temperatures {below 20 / above 90 0C / smaller intervals / eq };
7. reference to one other suitable variable e.g. time beetroot pieces left between cutting and use ;
8. reference to {calibration / zeroing / eq} of colorimeter ;
What have antiviral drugs been developed to treat people with? - ANSWER-Patients infected with HIV
2 Anti-viral drugs have been developed to treat patients infected with Human Immunodeficiency Virus
(HIV).
The diagram below shows the structure of HIV.
A glycoprotein has a carbohydrate attached to a protein molecule. Describe the 3D structure of a
glycoproteind - ANSWER-1. proteins consist of amino acids joined together by peptide bonds;
2. credit reference to named bonds (between R groups) involved in holding {3D structure / eq} ;
3. carbohydrates consist of {monsaccharides / glucoses / eq} ;
4. reference to glycosidic {bonds / eq} between (adjacent) {glucose / eq} molecules ;
Using the information in the graph and your knowledge of membrane structure, explain the effect of
temperature on the cell membranes - ANSWER-1. idea that the drugs could {bind to / alter shape of}
{glycoproteins / gp120} ;
2. idea that drugs bind to {receptors / antigens} on membrane / eq ;
3. called CD4 (antigen / molecules) ;
4. preventing virus attaching to T (helper / CD4+) cells / eq ;
Using all the information given in the question, describe how this investigation could be carried out to
provide valid and reliable results - ANSWER-1. reference to reverse transcriptase ;
2. idea of formation of (viral) DNA ;
3. from (viral) RNA ;
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