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CAIE A-Level Biology 4.1 Fluid Mosaic Membranes Question Bank

Practise fluid-mosaic membrane questions by labelling bilayer components, explaining cholesterol effects and outlining ligand-receptor signalling.

Syllabus
2028–2030
Course
Biology 9700
Level
AS

Exam points

  • label phospholipids, cholesterol, proteins, glycolipids and glycoproteins on membrane diagrams
  • explain fluidity, stability and permeability using fatty acid tails, cholesterol and bilayer movement
  • outline cell signalling from ligand secretion and transport to receptor binding and cell response

Covered syllabus points

4.1.1—Fluid mosaic membrane model4.1.2—Membrane component arrangement4.1.3—Role of membrane components4.1.4—Cell signalling process

4.1 Fluid Mosaic Membranes question 1

[Maximum number: 4]

Question (a)

(a)

Fig. 1.1 is a diagram representing part of the phospholipid bilayer of a cell surface membrane.

Fig. 1.1

Fig. 1.1

[ 2 ]

Question (i)

(i)

Cholesterol is an important lipid component of many cell surface membranes. Fig. 1.2 shows the structure of a cholesterol molecule.

Fig. 1.2

Fig. 1.2

Using the information in Fig. 1.2, explain the orientation (positioning) of cholesterol molecules in the phospholipid bilayer, as shown in Fig. 1.1.

[ 1 ]

Question (ii)

(ii)

State one role of cholesterol in phospholipid bilayers.

[ 1 ]

Question (b)

(b)

Prostaglandins are small lipids produced in many tissues of the body. One role of prostaglandins is to cause inflammation at the site of an injury or infection. Inflammation is the normal first response of the immune system to injury or infection.

Cyclooxygenase (COX) is an enzyme that catalyses one of the steps in the reaction pathway for the formation of prostaglandins from phospholipids. The reaction pathway occurs in the smooth endoplasmic reticulum (SER) of cells. Part of the reaction pathway is shown in Fig. 1.3.

Fig. 1.3

Fig. 1.3

[ 2 ]

Question (i)

(i)

Prostaglandins are examples of cell-signalling molecules.

Outline the process of cell signalling that leads to a response by the cells involved in inflammation.

[ 2 ]
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