Presentation on theme: "Chapter 5 Homeostasis & The Plasma Membrane. It’s all about balance! Failure to adjust….death Cells maintain balance by controlling materials entering/leaving."— Presentation transcript:
Most lipids have two fatty acids attached to glycerol The third fatty acid is replaced by a phosphate group-phospholipid Phospholipids-polar, water-soluble head + long, nonpolar, insoluble tail Align to form double layer with “heads” on outside and “tails” on the inside
Diffusion Cells maintain homeostasis by controlling the movement of substances across the membrane Cells must use NRG to transport some substances…..Ex- Active Transport! Other substances move across the membrane with no NRG required
Diffusion Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration. Goal of diffusion=Dynamic Equilibrium Continuous movement with no concentration change Concentration gradient-difference in concentration across space
Osmosis-Diffusion of Water Osmosis is the diffusion of water molecules through a selectively permeable membrane Movement from high to low concentration Type of passive transport! Isotonic solution-concentration of dissolved substances equal to concentration inside the cell…..NO NET MOVEMENT!
Hypotonic vs Hypertonic Hypotonic-solution where concentration of dissolved substances is lower than inside the cell Water moves into cell…swelling! Increases cell pressure-Turgor Pressure Hypertonic-solution where concentration of dissolved substances is higher than inside the cell Water moves out of cell…Plasmolysis
Protists Have contractile vacuoles that actively remove water from the cell.
Crossing the Membrane Diffusion through ion channels: Ion Channels- transport proteins with polar pores that ions can pass through. Pore is the thickness of the membrane Ion does not have touch the nonpolar interior of the bilayer.
Active Transport In order to move particles from a lower concentration to higher concentration a cell must use energy…Active Transport Proton pumps- specialized proteins for pushing different substances against the concentration gradient. Need ATP for energy!!!!!
Sodium-Potassium Pump Four Steps to the Pump: 1. Three Na ions attach to the pump. 2. Pump changes shape, transporting the ions across the membrane. 3. Two K ions outside bind to the pump 4. Two K ions are transported are released inside the cell.
Transport of Large Particles Endocytosis-process in which cell surrounds and takes in material from its environment Engulfed and enclosed by portion of cell membrane Exocytosis-expelling wastes from interior to exterior environment