B. Osmosis How is osmosis different from diffusion? It only deals with movement of water
Isotonic: same concentration of dissolved particles inside and outside of cell; cell stays the same size Three Types of Solutions Hypotonic: less dissolved particles outside cell than in cell; cell gains water and swells Hypertonic: more dissolved particles outside cell than in cell; cell loses water and shrinks
Practice Problem: Sea water has a higher concentration of salt than human body cells have. Why might drinking large amounts of sea water be dangerous for humans?
Facilitated diffusion is passive transport of materials across the plasma membrane with the aid of transport proteins. Molecules such as sugars or amino acids enter the cell through facilitated diffusion Channel protein shown at right – provides a tubelike opening for small molecules C. Facilitated Diffusion
Carrier proteins change shape to let larger molecules into the cell
Cells use energy to transport materials against the concentration gradient II. Active Transport
Active transport is powered by chemical energy (ATP). Active Transport Active transport occurs through transport proteins
A cell can import large materials in vessicles during the process of endocytosis. Cells use energy to transport material in vessicles. Endocytosis