Lab 4 Osmosis PDF

Lab 4 Osmosis Normal and plasmolysis cells Background Cell membranes help organisms maintain homeostasis by controlling what substances may enter or leave cells by its semipermeable membrane. There are two types off passive transpor...

Lab 4 Osmosis Normal and plasmolysis cells Background Cell membranes help organisms maintain homeostasis by controlling what substances may enter or leave cells by its semipermeable membrane. There are two types off passive transport that don’t need any energy , diffusion and osmosis. Osmosis: a process by which the molecules of a solvent pass from a solution of high concentration of solvent to a solution of low concentration of solvent through a semi- permeable membrane. The same definition in other words: the movement of solvent molecules from a solution of low concentration of solute to a solution of high concentration of solute. In most cases, the solvent will be water because water is the universal solvent. Osmotic solutions: there are three types of osmotic solution 1) isotonic solution is one that has the same concentration of solutes both inside and outside the cell. An example to isotonic solution for red blood cells is 0.9% NaCl, you can consider the same for plant cell in our experiment. 2) hypertonic solution is one that has a higher solute concentration outside the cell than inside. 3) hypotonic solution is one that has a lower solute concentration outside the cell than inside. Effect of Osmosis on Cells Osmosis affects the cells differently. An animal cell will burse when placed in a hypotonic solution compared to a plant cell. The plant cell has thick walls and requires more water. The cells will not burst when placed in a hypotonic solution. On the other hand, the plant cell when put in hypertonic solution will be plasmolyzed cell, a cell that lost its cytoplasm and shirked in response to movement of water from inside to outside of the cell. Objective Distinguish between the osmotic solution and their effect on the animal and plant cells Materials Compound microscope. NaCl solution different concentration: 6%, 0.1% or distilled water, 0.9% or tap water. Microscope slides and cover slips. Forceps and scalpel. Purple Onion epidermis. Marker pen Procedure 1) Collect a segment of red onion and all other materials. 2) Label 3 microscope slides: 0.1% NaCl, 6% NaCl, 0.9% NaCl 3) Peel a thin layer of epidermis from a red surface of the onion. Place it on the slides. 4) Add 1‐2 drops of the three solutions to cover the tissue , separately. 5) Place a coverslip over the tissue. 6) View the samples under the compound light microscope at an appropriate magnification (usually 100x or 400x). It helps to close the iris diaphragm to some degree to increase contrast and see the cell walls clearly. Results Make an annotated diagram of your results. Record the magnification. Estimate cell size (if you have previously calibrated your microscope). (For Applied Biology students only) Label all structures observed. If possible, photograph the cells in the microscope view and include a print in your log book  Lab 4 report Introduction --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- Objectives --------------------------------------------------------------------------------------------------------------------- Materials --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- Procedure --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- Results ----------------------------- ------------------------------- -------------------------- ----------------------------- ------------------------------- -------------------------- Discussion 1) Discuss your results --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------  2) Why its preferred to use purple onion not white onion in this experiment ------------------------------------------------------------------------------------------------------------ 3) Why is osmosis important for the cells? --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- 4) How is osmosis different from diffusion? --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- 5) List of some examples of osmosis 1)----------------------------------------------------2)----------------------------------------------------------- 3)-----------------------------------------------------3)---------------------------------------------------------- 6) What is a semipermeable membrane? --------------------------------------------------------------------------------------------------------------------- 7) Do you think hypotonic solution is bad for the plant cell? why --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- 8) What is the relationship between dialysis and osmosis? --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- The end