Levels of Organization
Unit 5: Membrane Structure and Function
Learning Objectives
At the end of this unit, you should be able to:
I. Describe the “fluid mosaic” model of membrane structure including the membrane components.
II. Describe how the structure of the cell membrane affects membrane permeability.
III. Describe the following passive processes: diffusion, facilitated diffusion and osmosis. Explain the function of each in a cell.
IV. Describe and explain the effects of placing red blood cells in hypertonic, hypotonic and isotonic solutions, respectively.
V. Describe the following active processes: primary and secondary active transport, endocytosis (phagocytosis, pinocytosis), and exocytosis. Explain the function of each in a cell.
Learning Objectives and Guiding Questions
At the end of this unit, you should be able to complete all the following tasks, including answering the guiding questions associated with each task.
I. Describe the “fluid mosaic” model of membrane structure including the membrane components.
- Describe the characteristics of the plasma membrane that are captured by describing its structure as a ‘fluid mosaic’. (i.e.: explain why it is appropriate to refer to the membrane as ‘fluid’ AND why it is appropriate to refer to the membrane as a ‘mosaic’.)
II. Describe how the structure of the cell membrane affects membrane permeability.
- Describe how the structural components of the plasma membrane make it “selectively permeable”, rather than permeable or impermeable. In your description be sure to refer to the types of molecules that may pass easily (or not) through the membrane, and what chemical characteristics they share that makes them capable (or incapable) of doing so.
III. Describe the following passive processes: diffusion, facilitated diffusion and osmosis. Explain the function of each in a cell.
IV. Describe and explain the effects of placing red blood cells in hypertonic, hypotonic and isotonic solutions, respectively.
- Describe and explain the effects (i.e.: on cell size, cell shape, and cytosol solute concentrations) of placing red blood cells in a solution that is:
- Hypertonic relative to the cytosol
- Hypotonic relative to the cytosol
- Isotonic relative to the cytosol
V. Describe the following active processes: active transport, endocytosis (phagocytosis, pinocytosis), and exocytosis. Explain the function of each in a cell.
- Compare and contrast (with the use of annotated diagrams) the characteristics of the following in terms of (a) ATP requirements, (b) molecules moved, (c) size of material moved, and (d) the direction of movement (i.e.: relative to its own concentration gradient, relative to another molecule or molecule type’s concentration gradient, and/or relative to the cell’s internal vs. external environment):
- Active and passive transport mechanisms
- Simple and facilitated diffusion
- Facilitated diffusion and osmosis
- Facilitated diffusion and secondary active transport
- Exocytosis and endocy