Page 15 - Q & A STPM 2022 Biology

Biology STPM Chapter 3 Membrane Structure and Transport

Question 2
Four groups of potato cells, each with a water potential [ψ] of –300 kPa are
placed in four solutions P, Q, R and S of different water potentials.
In which of the four solutions will there be a net movement of water molecules
Penerbitan Pelangi Sdn Bhd. All Rights Reserved.
into the potato cells?
Solution Water potential, ψ (kPa) Semester
A P 0
B Q –300 1
C R –500
D S –700

Answer : A
Pure water has the highest water potential, (ψ=0). Water will diffuse from a
region of higher water potential (less negative or zero value) to a region of
lower water potential (more negative value) until the concentration of water
molecules in both areas are equal.

Question 3
Which of the following curves best shows the relationship between the
concentration outside the membrane and the movement rate through the
membrane by simple diffusion and facilitated diffusion respectively?
Movement rate

d
a c
b

Concentration
outside membrane
Simple diffusion Facilitated diffusion
A d b
B d c
C c a
D c d

55

Chapter 3.indd 55 11/2/21 9:21 AM