1.3: Membrane structure

prior learning & retrieval practice

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

S1: Drawing of the fluid mosaic model.

Exercise 1: Draw the structure of the fluid mosaic model of cell membranes.

U1: Phospholipids form bilayers in water due to the amphipathic properties of phospholipid molecules.

Exercise 2: Define the following terms and add them to your glossary: phospholipid, hydrophobic, hydrophilic, amphipathic.

Exercise 3: Outline the amphipathic properties of phospholipids and explain why this makes them form bilayers.

U2: Membrane proteins are diverse in terms of structure, position in the membrane and function.

Exercise 4: Create a table that outlines the structure, position and function of different membrane proteins.

A1: Cholesterol in mammalian membranes reduces membrane fluidity and permeability to some solutes.

U3: Cholesterol is a component of animal cell membranes.

Exercise 5: Answer the following questions:

• • What is Chloesterol?

  • Where in the fluid mosaic model is it found?

  • What affect does it have on the membranes?

  • What solutes does it reduce the permeability of the membrane to?

NoS: 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Falsification of theories with one theory being superseded by another—evidence falsified the Davson-Danielli model.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)

S2: Analysis of evidence from electron microscopy that led to the proposal of the Davson-Danielli model.

Exercise 6: Outline the electron microscopy evidence that led to the proposal of the Davson-Danielli model

S3: Analysis of the falsification of the Davson-Danielli model that led to the Singer-Nicolson model.

Exercise 7: Outline the evidence that led to the falsification of the Davson-Danielli model and the proposal of the Singer-Nicolson model.