p88 Q 4
a. The water
potential of rbc cytoplasm is hypertonic to (lower than) distilled water. There
is a net water movement into rbc and pressure is being built up. The rbc burst eventually
and the (red) cell content leaches out to the solution. It is the reason that
the test tube A shows red colour.
The net water
movement is reversed in the test tube C. The rbc shrinks and saline keeps
clear.
b. The water
potential of solution B may slightly higher than that of rbc cytoplasm. Some of
the rbc with “weak membrane” burst, so the solution is lighter red colour.
c. Observation on
the solid matters will find some cell fragments (burst cell without cell
content)
d. The
single-celled animals lose water in hypertonic solution
p 89 Long Q 1
a. Draw your own
graph.
b. Your data
should be in between 45-90.
c. Repeat
experiment with concentrations between 45 to 90 with smaller interval, e.g. in
steps of 5
d. Work out by
extrapolation of the graph.
e. As the tissue
was placed in 0.25mol dm-3 solution, the mass of the tissue
increases up to 4% gradually. Once the tissue was taken out, blotted dried and
immersed into 1.0mol dm-3 solution, the mass of the tissue decreased
gradually. It is because the 1.0mol dm-3 solution is hypertonic to
the cytoplasm. Since the tissue was placed in hypotonic solution before, the
some of the tissue cells may be killed and the cell membranes of those death
cells were fully permeable. Time may not enough for mass change from +4% to –7%
within 2 hours, so the %mass change may not be –7% as shown in the data.