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CAIE A-Level Biology 4.2.1 Membrane Transport Processes

Practise distinguishing diffusion, facilitated diffusion, osmosis, active transport, endocytosis and exocytosis from gradient direction, proteins, ATP and vesicles.

Syllabus
2028–2030
Course
Biology 9700
Level
AS

Exam points

  • identify passive movement down a gradient as simple or protein-mediated facilitated diffusion
  • define osmosis as net water movement down a water-potential gradient through a permeable membrane
  • recognise ATP-driven pumps and vesicle-based endocytosis or exocytosis from their mechanisms

4.2.1—Membrane transport processes question 1

[Maximum number: 4]

Question (a)

(a)

Explain why sodium ions cannot cross phospholipid bilayers by simple diffusion.

[ 1 ]

Question (b)

(b)

Ions and some molecules move across cell surface membranes by facilitated diffusion and active transport.

Compare facilitated diffusion and active transport by stating one way in which they are similar and two ways in which facilitated diffusion is different from active transport.
similarity
difference 1
difference 2

[ 3 ]
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