Essential idea: The structure of biological membranes makes them fluid and dynamic.

Q1-5: These questions refer to this diagram of a cell membrane:

cell membrane detailed

1. The thickness of the cell membrane (Z) is:
  • A. 7.5 – 10 nm
  • B. 7.5 – 10 mm
  • C. 7.5 – 10 µm
  • D. 7.5 – 10 cm
2. The molecules making up the two layers in Z are:
  • A. Phospholipids
  • B. Carbohydrates
  • C. Lipids only
  • D. Proteins
3. Molecule T is ...
  • A. cholesterol
  • B. channel protein
  • C. integral protein
  • D. peripheral protein
4. The phospholipid molecules are described as amphipathic. This means that ...
  • A. the molecules form a bilayer
  • B. part of the molecule attracts water whilst a different part repels water
  • C. the molecules are bipolar
  • D. the molecules are found on the outside of the membrane
5. Which structure reduces the fluidity of the membrane?
  • A. W
  • B. U
  • C. T
  • D. V
6. Using Electron micrographs The Davson-Danielli model of membrane structure was formulated in the 1950s.

What did the Davson-Danielli model of membrane structure suggest?

  • A. A phospholipid monolayer with intrinsic and extrinsic proteins
  • B. A layer of protein sandwiched between two layers of lipid
  • C. A phospholipid bilayer with intrinsic and extrinsic proteins
  • D. A layer of lipid sandwiched between two layers of protein

7. Which of the following pieces of evidence falsified the Davson-Danielli model of the structure of the cell membrane and lead scientists to adopt the Singer-Nicolson model?

I. Globular structures scattered through freeze-etched images of the centre of membranes.
II. Biochemical analysis identified many different types of structural proteins in the membrane.
III. Fluorescent tagging showed that proteins were free to move within the membrane.

  • A. I only
  • B. I and II
  • C. II and III
  • D. I, II and III
8. The function of the cell membrane is to form a barrier through which ions and hydrophilic molecules cannot easily pass.

Which molecules carry out this function?

  • A. Cholesterol
  • B. Integral proteins
  • C. Phospholipids
  • D. Peripheral proteins
9. Which of the following helps maintain the structure of the cell membrane?
  • A. Hydrophobic interactions between fatty acid chains
  • B. Hydrophobic interactions between phosphate heads
  • C. Hydrophilic interactions between water and fatty acid chains
  • D. Hydrogen bonding between water and cholesterol
10. Animal cells may secrete glycoproteins as extracellular components. What is the role of these glycoproteins?
  • A. Increase cell adhesion
  • B. Enhance membrane fluidity
  • C. Increase water uptake
  • D. Aid cell to cell communication