OCR
A-LEVEL
BIOLOGY
Foundations in Biology
Biological Membranes 1
Time allowed
74 minutes
QUESTION PAPER
Score Percentage
/62 %
4.1 | CELL BIOLOGY | QUESTION PAPER 1 1
, 1 (a) Describe the structure of a plasma (cell surface) membrane.
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(b) A student investigated the movement of substances through the cell surface membrane of
yeast cells using an indicator.
• The student was supplied with a suspension of yeast cells in a slightly alkaline solution.
• The indicator used is yellow in alkaline conditions but turns red in acidic conditions.
The student mixed the indicator with the yeast suspension and labelled the tube containing
this suspension A. The suspension was red/pink in colour.
(i) The student took a small sample from tube A and centrifuged this sample.
After centrifuging, the student observed that the liquid portion was colourless but the
cells at the bottom were red/pink.
Suggest the mechanism by which the indicator enters the cells and suggest the
component of the membrane involved.
mechanism ........................................................................................................................
component ................................................................................................................... [2]
(ii) The student took a small sample from suspension A and added alkaline ammonia
solution. There was no colour change.
What could the student conclude about the permeability of the yeast plasma membrane?
...........................................................................................................................................
...................................................................................................................................... [1]
PhysicsAndMathsTutor.com
A-LEVEL
BIOLOGY
Foundations in Biology
Biological Membranes 1
Time allowed
74 minutes
QUESTION PAPER
Score Percentage
/62 %
4.1 | CELL BIOLOGY | QUESTION PAPER 1 1
, 1 (a) Describe the structure of a plasma (cell surface) membrane.
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
.............................................................................................................................................. [3]
(b) A student investigated the movement of substances through the cell surface membrane of
yeast cells using an indicator.
• The student was supplied with a suspension of yeast cells in a slightly alkaline solution.
• The indicator used is yellow in alkaline conditions but turns red in acidic conditions.
The student mixed the indicator with the yeast suspension and labelled the tube containing
this suspension A. The suspension was red/pink in colour.
(i) The student took a small sample from tube A and centrifuged this sample.
After centrifuging, the student observed that the liquid portion was colourless but the
cells at the bottom were red/pink.
Suggest the mechanism by which the indicator enters the cells and suggest the
component of the membrane involved.
mechanism ........................................................................................................................
component ................................................................................................................... [2]
(ii) The student took a small sample from suspension A and added alkaline ammonia
solution. There was no colour change.
What could the student conclude about the permeability of the yeast plasma membrane?
...........................................................................................................................................
...................................................................................................................................... [1]
PhysicsAndMathsTutor.com
