The cell membrane, diffusion and osmosis Caylor Day Five The cell membrane, diffusion and osmosis

Journal 5 Complete the Venn diagram below: Animal Cell Plant Cell 1. 2. 1. 2. 1. 2.

Describe the functions of the cell membrane. Provides boundary for cell Controls flow in and out of cell Selectively permeable Maintains homeostasis: balance within the cells

Relate the structure of the cell membrane to its function. Membrane is a lipid bilayer Made up of molecules which are free to move; called fluid-mosaic Phospholipids: fatty areas that attract and repel water; makes membrane behave like a fluid Embedded proteins: determine which particles can pass through Also serve as recognition markers Form channels from one side of the cell to the other

Compare diffusion and osmosis. DIFFUSION: movement of particles from high concentration to low concentration Causes substances to move across membrane Does not require the cell to use energy Substances move across membrane until there are equal amounts on either side: EQUILIBRIUM

OSMOSIS: diffusion of water through a membrane How osmosis works: water moves from where there is a lot to where there is a little until equilibrium is reached Osmosis exerts pressure (OSMOTIC PRESSURE) which can cause some problems for certain cell swelling Higher Concentration of Water Water molecules Lower Concentration of Water Sugar molecules

Quiz 5 Which of the following is NOT found in the plasma membrane? a. phospholipids b. proteins c. plasma If a cell only lets certain things in and certain things out, it is referred to as ___. a. permeable b. selectively permeable c. osmotic ___ is the movement of particles from high concentration to low concentration. a. diffusion b. selectively c. osmosis Since the plasma membrane moves around the surface of the cell, it is called a ___ model. a. fluid-mosaic b. passively transported c. static If a salt water worm is placed in a container of fresh water, what would happen to the worm? a. it would shrink up b. nothing c. it would swell up Quiz 5