Learning Objectives

Section 5.1 How Is the Structure of a Membrane Related to Its Function?

• Describe the major functions of cell membranes.
• Explain the fluid mosaic model of cell membranes.
• Explain how the polar nature of phospholipids gives rise to the membrane structure.
• Describe how the hydrophobic tails of phospholipids contribute to isolating the cell from its environment.
• Describe the functions of the five different types of membrane proteins.

Section 5.2 How Do Substances Move Across Membranes?

• Discuss the relationship between the terms solute, solvent and concentration.
• Explain how random motion combined with a concentration gradient results in diffusion.
• Describe the external factors affecting the rate of diffusion.
• Discuss the major difference between passive and active transport.
• Explain the basis for the selective permeability of the membrane.
• Describe the differences and similarities between simple diffusion, facilitated diffusion and osmosis.
• Explain the terms isotonic, hypertonic and hypotonic and their relationship to osmosis between a cell and its environment.
• Explain how osmosis and turgor pressure provide support for plants.
• Explain why cells engage in active transport.
• Discuss the various types of endocytosis and exocytosis.
• Relate the process of diffusion to the size limit of a single cell.

Section 5.3 How Do Specialized Junctions Allow Cells to Connect and Communicate?

• Describe the structural and functional differences between desmosomes, tight junctions and gap junctions.
• Describe the structure and functions of plasmodesmata.