This essay focuses on : Osmosis and Diffusion in Elodea. Please provide your instructor a copy of the Memorandum of Accommodation
BIO 101 Lab 05: Osmosis and Diffusion in Elodea and Red Blood Cells.
Notification: If you have a disability that makes it difficult to complete this lab, please contact your instructor. Please provide your instructor a copy of the Memorandum of Accommodation (MOA) from NVCC Disability Support Services.
Firstly, Review cell membrane structure and the components that make it a semipermeable barrier.
Secondly, Observe plant and animal cells placed in solutions, hypotonic, isontonic, and hypertonic to the cells and observe the effect of each of the solutions on the cells.
Thirdly, Observe plazmolyzed and turgid and flaccid plant cells.
Further, Observe healthy red blood cells, crenated and hemolyzed blood cells.
Further, Interpret images of plant cells or red blood cells in different solutions.
Cells and Cell Membrane structure
Living cells are filled with an aqueous solution, the cytosol. Many small solutes or particles, are dissolved in this watery cytosol, including ions, nutrients, waste and enzymes. Larger organelles (such as mitochondria and chloroplasts) and large complexes of molecules (e.g. ribosomes) are also located in this cytosol; organelles and complexes combine with the cytosol to form the cytoplasm of cells.
(plasma membrane). Because the cell membrane is comprised of both phospholipids and proteins it is semi-permeable: select molecules can easily pass through the phospholipid bilayer, while other molecules cannot. Phospholipids are comprised of hydrophobic fatty acid tails and polar phospho- heads. In the bilayer, the fatty layers are sandwiched in between the hydrophilic polar heads; one layer of polar heads lines the inside (cytosolic face) of the cell membrane and a second polar head, lines the outside of the cell membrane or surface.
Molecules that can easily pass through a cell membrane are small and nonpolar, such as gases: oxygen, carbon dioxide, and nitrogen. Hydrophobic lipids, (fats and steroids) can dissolve in the hydrophobic fatty layer of the cell membrane and also will diffuse into or out of a cell.
Some small molecules (e,g. sugars) and ions (sodium or chloride) can diffuse across a membrane if there is a protein (transport protein or ion channel) These small solutes will move from areas of high concentration to low concentration through a select protein that is part of the membrane.\
Osmosis occurs when water moves down its gradient. Active transport occurs when a solute, such as sugar, moves against its gradient. Both energy and protein transporters are required for active transport to occur.
Osmosis is a type of diffusion
Osmosis occurs when water moves by diffusion across a membrane from high water concentration to low lower water concentration. In this case, the solutes are not diffusing because they have positive or negative charge or are too large, and their protein transporter are closed.
Tonicity. Three terms refer
to the concentrations of solutes in which a cell or organism is place:
● Isotonic solutions have an equal concentration of solutes outside a cell as the cytosol in the cell
(is also referred to as having an equal osmotic pressure)
lower solute concentration outside a cell than the cytosol in the cell
● Hypertonic solutions have a higher solute concentration inside a cell than the cytosol in the cell.
Historic methods of food preservation have relied on the principle of osmosis. By placing foods (vegetables, fruits and meats) in a salty solution, call brine, or a sucrose solution, water is draw out of the cells by osmosis. The result is a preserved or dry food which is much less likely to spoil; some examples are sauerkraut, beets, salted cod and ham. While these methods for preserving food have a long history, they remain useful today.