1.3 Cell membrane structure

1.3  Cell Membrane structure 

Lesson one

Objectives: Understand what is meant by the ampiphatic phospholipid bi-layer. Understand the role of membrane proteins and cholesterol. Understand that the Singer-Nicholson model for membrane structure has replaced the Davson-Danielli model.


  • Ampiphatic: having a hydrophilic (water-loving) and a hydrophobic end (water-hating)
  • Phospholipid: the backbone molecule of the cell membrane. Made from a phosphate group and two fatty acid chains, joined through glycerol.
  • Integral proteins: proteins which span the cell membrane
  • Peripheral proteins: proteins which are embedded in the surface of a cell membrane

Cell membranes surround all cells, as explained in cell theory. Cell membranes also enclose many eukaryotic organelles, e.g. lysosomes. Some organelles have a double membrane eg. chloroplast, mitochondria, nucleus. Perhaps surprisingly, they all have much the same structure.

image credit: cronodon

image credit: cronodon

  • A: Phospholipid A1 phosphate, A2 fatty acid chains
  • B: Glycolipids
  • C: Glycoproteins
  • D: Carbohydrate group
  • E: Cholesterol
  • F: Peripheral protein
  • G: Integral protein






Follow slides Slides 1-7 in the powerpoint below


[slideshare id=52257087&doc=c-150831160046-lva1-app6891]

Task: Model the cell membrane with plasticine. This is an example from an IB Biology class at the Lincoln school. Can you interpret it?


Task: Draw the cell membrane, using the Singer-Nicolson fluid mosaic model.

[slideshare id=52022804&doc=c-150824214449-lva1-app6891]


Task: The cell membrane story. Review the history of the evidence that led to the falsification of the Davson-Danielli cell membrane model and the acceptance of the Singer-Nicolson cell membrane model

Task: Draw the cell membrane from memory. Be careful to use sharp, unbroken lines to show outlines. Label clearly, and indicate the size of the cell membrane (7.5nm thick)

Just for fun: A class challenge! image


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