BI110 Lecture Notes - Lecture 14: Electrochemical Gradient, Cell Membrane, Facilitated Diffusion
Document Summary
Is the plasma membrane impermeable: the plasma membrane is selectively permeable, semipermeable. Diffusion: there is net movement of solute from the area of high concentration to an area of low concentration, when concentrations are equal there is no movement of solute but diffusion continues. Whereas, symporters/uniporters move molecules in the same direction. Effects of osmosis: hypertonic solutions have a higher solute concentration than inside the cell. Isotonic is normal when concentration of water is the same inside and outside the cell: hypotonic solutions have a lower solute concentration than inside the cell. Plant cell wall and vacuoles: cell wall are external to the plasma membrane, help to maintain cell shape in plants, fungi and bacteria, the force exerted by water pressing against an object is turgor pressure (hydrostatic pressure) In plant and fungal cells, the vacuole also absorbs water and contributes to turgor pressure.