Passive Transport Worksheet

Passive Transport It Just Happens//! The job of the cell membrane is to regulate what enters and exits the cell. The cell membrane acts in a way that is similar to the doors and windows of your house. Since some "stuff" can come in and some "stuff" must stay out, the cell membrane is said to be selectively permeable. For the most part, your cell membrane does not have to work very hard in order to perform its job. Small molecules and molecules that do not have a charge can easily pass through the cell membrane without any energy required by the cell. This type of movement, when no energy is required, is called Passive Transport (no energy required - it just happens). Passive Transport always happens when molecules that are in a high concentration area (crowded area) have the opportunity to move to a lower concentration area (less crowded area). Molecules will always move to areas where it is less crowded for them, without any energy needed. This movement of molecules from a high concentration area to a low concentration area is called "moving down the concentration gradient (concentration difference)". If you think about it, don't all things move "down" without any energy required? There are 3 types of passive transport that you will have to know - Diffusion, Osmosis and Facilitated Diffusion. Remember that all 3 are passive transport - no energy required, all movement is from high concentration to low concentration! Diffusion is when any molecule moves from high to low concentration. Osmosis is when water moves from high to low concentration. Facilitated Diffusion is when large or charged molecules move from high to low concentrations through a channel protein in the cell membrane. The channel protein is similar to a "doggie door" in your house - it is just the right size hole for your dog to enter or exit without any energy required by you! Since molecules will always move from high to low concentrations, living things use this mechanism of transport for most substances. When you breathe in air with a high concentration of oxygen in it, yet your blood has a lower concentration of oxygen - the oxygen will simply diffuse into your blood cells! If your blood fluid has a higher concentration of water than your cells, then osmosis will occur into your cells! If your blood sugar concentration is higher than your muscle cells, then facilitated diffusion will occur through channel proteins! In addition, because of this natural movement of molecules, living things must keep water, sugar, salts, etc. at a constant level (homeostasis) to prevent major problems from occurring. Your body tries to maintain fluids in your body that are Isotonic to your cells (same concentrations). That way movement still happens in and out of the cell but it is in equilibrium - same amounts are going in as coming out. If your body fluids became Hypotonic (high water concentration, little sugars & salts) compared to the cells, the cells would fill up with too much water and burst. If your body fluids became Hypertonic (low water concentration, and lots of sugars & salts), water would leave your cells and your cells would shrivel up and die! In conclusion, most molecules will move in or out of cells without any energy required - passively! To test your knowledge of passive transport, color the following diagrams and answer the analysis questions on the following page. lF���[lJu�u�[Q) ulR1�lM�[p)(Q)lR1u* @[lJLJJ�(Q)�� [MJ(Q)[L��(UJ[L�F �lR1Wu[l={]lR1(Q)�Wu�A [p)(UJ[R1� w�u�lR1s (Ot®�o/@ ��[Lu �(Q)[L(UJu�(Q)lMc �o/@ ��[LLi �(Q)[L(UJ1J�(Q)[M o I\ o,,Y·•_.,;_ .. ';.\;.;_.;.: .-. A B c. 1>