Passive Transport (A) FILLED IN PDF

Transport in Cells In order for cells to maintain homeostasis, they must have a way of moving substances through the cell membrane. The cell membrane controls movement of dissolved molecules from the solution on one side of the cell membrane to the solution on the other side. The concentrat...

Transport in Cells In order for cells to maintain homeostasis, they must have a way of moving substances through the cell membrane. The cell membrane controls movement of dissolved molecules from the solution on one side of the cell membrane to the solution on the other side. The concentration of a solution is the amount of solute in a liquid (solvent). HIGH concentration means LOTS of solute.  What is concentration? In order to measure the concentration of a solution, you find out the mass of the solute in the solution and divide it by the volume of solvent. For example, if you dissolved 12 grams of salt (solute) into 3 liters of water (solvent), the concentration would be: 12g / 3L = 4 g/L (grams per liter!) ***There are two kinds of ways that the cell regulates solute concentration in cells: passive and active transport.***  Methods of Cell Transport Passive Transport Active Transport Diffusion Protein Pumps Facilitated Endocytosis Diffusion Exocytosis Osmosis  Passive Transport: Diffusion In diffusion, molecules move from an area of higher concentration to an area of lower concentration without using energy The solute particles will continue to move until equilibrium is reached (same amount of solutes on both sides of the membrane).  Diffusion Through Cell Boundaries Solutes always move DOWN their concentration gradient (from high to low concentration). Even solutes want some space for themselves! There is a higher Solute move from high When equilibrium is concentration of concentration to low reached, solute solute on one side of concentration (HIGH particles continue to the membrane as LOW). The solute will diffuse across the compared to the other continue to diffuse membrane in both side of the membrane. across the membrane directions. until equilibrium.  Rate of Diffusion 3 factors affect how fast diffusion occurs: – Concentration: diffusion is faster at higher concentrations – Temperature: diffusion is faster at higher temperatures – Pressure: diffusion is faster at higher pressures  Diffusion: Non-polar molecules Small, non-polar molecules diffuse easily across the phospholipid bilayer of a membrane Example: – In our lungs, passive transport down concentration gradients is how oxygen (a small, non-polar molecule) enters red blood cells & carbon dioxide leaves them  Facilitated Diffusion Molecules that are too big, polar, or Glucose charged cannot move through the lipid molecules bilayer on their own They use the help of a protein When a protein facilitates the diffusion of a molecule from high to low concentration, it is called facilitated Glucose diffusion protein channel Each facilitator protein is specific to each kind of molecule (for example, glucose can only go through glucose facilitator proteins).  Passive Transport: Facilitated Diffusion Channel Proteins Carrier Proteins open and close to allow change shape to help substances to diffuse move particles through through the plasma the membrane membrane  Osmosis In osmosis, water diffuses through a selectively permeable membrane. Water will always move from where there is MORE water (high concentration of water) to where there is LESS water (lower concentration of water).  Passive Transport: Osmosis When a cell is in a solution, that solution may be hypertonic, hypotonic, or isotonic to the cell. Hypertonic- when a solution has a higher concentration of solutes (and less water) than the cell Hypotonic- when a solution has a lower concentration of solutes (and more water) than the cell. Isotonic- when a solution has the same concentration of solutes as the cell.  Isotonic Hypotonic Hypertonic Solution with same Solution with Solution with higher solute concentration as lower solute conc. solute conc. than cell cell than cell (water (water moves OUT moves INTO cell) of cell)  Draw a cell in a hypertonic environment Which way will the water = solute travel? molecule Cell 13  Draw a cell in a hypotonic environment Which way will the water = solute travel? molecule Cell 14  Draw a cell in a isotonic environment Which way will the water = solute travel? molecule Cell 15  Practice Problem #1 Steps: 1.Compare the solute percentages only. a) If the solution has MORE solute, then it is hypertonic. b) If the solution has LESS solute, then it is hypotonic. 60% water c) If the solution has the SAME 40% solute amount of solute, then it is isotonic. 2.Look at the water percentages only. Draw an arrow showing which way the water will travel (it will always go from the high percentage to the low percentage) 25% water 75% solute Hypertonic What type of solution is the cell in? ________________________  Practice Problem #2 Steps: 1.Compare the solute percentages only. a) If the solution has MORE solute, then it is hypertonic. b) If the solution has LESS solute, then it is hypotonic. 80% water c) If the solution has the SAME 20% solute amount of solute, then it is isotonic. 2.Look at the water percentages only. Draw an arrow showing which way the water will travel (it will always go from the high percentage to the low percentage) 10% water 90% solute Hypertonic What type of solution is the cell in? ________________________  Water Movement in Animal Cells Isotonic Hypotonic Hypertonic solution solution solution H2O H2O H2O H2O Anim al cell (1) (2) (3) Normal Lysed Shriveled In an isotonic In a hypotonic solution, a In a hypertonic solution, a solution, a cell stays cell gets very big and cell shrivels up normal swells  Osmoregulation in Animal Cells For an animal to survive in a hypotonic or hypertonic environment, it has to have a way to prevent excessive uptake or loss of water This control of water balance is called osmoregulation Example: a freshwater fish, which lives in a hypotonic environment, has kidneys and gills that work constantly to prevent excessive buildup of water in the body  Water Balance in Plants Water balance is different for plant cells because of their rigid cell walls A plant cell in an isotonic solution is flaccid, and non-woody plants (such as most houseplants) wilt In hypotonic environments, a plant cell is turgid and healthiest – The elastic cell wall expands a bit, but the pressure it exerts prevents the cell from taking in too much water and bursting In an hypertonic solution, a plant cell loses water and its plasma membrane pulls away from the cell wall, known as plasmolysis Isotonic Hypotonic Hypertonic Plasma H2O H2O H2O membrane H2O Plan t cell Flaccid Turgid Shriveled