Essential idea: The structure of biological membranes makes them fluid and dynamic.
Above is are models of a plasma membrane showing how it's fluidity allows lipid soluble molecules to move directly through the membrane.
Understandings, Applications and skills:
| 1.3.U1 | Phospholipids form bilayers in water due to the amphipathic properties of phospholipid molecules. [Amphipathic phospholipids have hydrophilic and hydrophobic properties.] |
| 1.3.U2 | Membrane proteins are diverse in terms of structure, position in the membrane and function. |
| 1.3.U3 | Cholesterol is a component of animal cell membranes. |
| 1.3.A1 | Cholesterol in mammalian membranes reduces membrane fluidity and permeability to some solutes. |
| 1.3.S1 | Drawing of the fluid mosaic model. [Drawings of the fluid mosaic model of membrane structure can be two dimensional rather than three dimensional. Individual phospholipid molecules should be shown using the symbol of a circle with two parallel lines attached. A range of membrane proteins should be shown including glycoproteins.] |
| 1.3.S2 | Analysis of evidence from electron microscopy that led to the proposal of the Davson-Danielli model. |
| 1.3.S3 | Analysis of the falsification of the Davson-Danielli model that led to the Singer-Nicolson model. |
[Text in square brackets indicates guidance notes]
Starters
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The cell membrane rap by Mr W
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Drawing the structure of the plasma membrane
a good knowledge check for the start of lessons, use the video to check your understanding and test yourself |
Presentation and notes
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The presentation is designed to help your understanding. The notes outline is intended to be used as a framework for the develop of student notes to aid revision.
VocabularyCorrect use of terminology is a key skill in Biology. It is essential to use key terms correctly when communicating your understanding, particularly in assessments. Use the quizlet flashcards or other tools such as learn, scatter, space race, speller and test to help you master the vocabulary.
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Labs
Membrane integrity
Investigating the effect of temperature on beetroot membranes n.b. this outline was written for the old syllabus, the document needs updating, but the lab is still a valid one. Concept mapping activity
Try out this mapping activity on membrane structure from BiologyForLife:
hint: one strategy is to first try to separate the phrases into small groups with obvious links, then link together the groups slowly making the map larger until all the cards are used. example of a completed map Quick Quiz
Quick quiz Use the BioK Quick Quiz on 1.3 Membrane structure (as directed) to check your understanding of the topic.
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Weblinks:
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Membrane structure
Phospholipid bilayer by the College of Siskiyous Membrane structure tutorial by Davidson College Construction of the cell membrane by Wisconsin online Membrane structure and the fluid mosaic model by Candle light productions Phospholipid membranes by Carnegie Mellon A series of helpful animation concerning biological membranes by Carnegie Mellon Membrane fluidity Membrane fluidity from Learn.Genetics Animated plasma membrane, by John Kyrk Membrane fluidity from John Gianni Origin of cells Exploring Life's Origins - the importance of membranes lipids to the development of cells is discussed in this well written article - this article links nicely with 1.5 Origin of cells _ |
Here's a fun musical interlude from the Standford biologists
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Nature of science:
Using models as representations of the real world—there are alternative models of membrane structure. (1.11)
Falsification of theories with one theory being superseded by another—evidence falsified the Davson-Danielli model. (1.9)
(both NoS points are well dealt with in the presentation)
Falsification of theories with one theory being superseded by another—evidence falsified the Davson-Danielli model. (1.9)
(both NoS points are well dealt with in the presentation)
Theory of knowledge:
The explanation of the structure of the plasma membrane has changed over the years as new evidence and ways of analysis have come to light. Under what circumstances is it important to learn about theories that were later discredited?
