Plasma Membrane Division Sam Mielke, Allie Mooney, Lauryn Robberstad

Fluid Mosaic Model The cell membrane is made out of a double layer of phospholipids. The cell membrane protects each cell from the external environment. The cell membrane also regulates what enters and exits the cell so the cell doesn’t lose its nutrients. It is made up of phospholipids, cholesterol, and proteins. The phospholipid part of the membrane is made up of a head (attracted to water) and two tails (repels water) . The membrane forms when water is introduced to the membrane the two layers form from the fact the the heads are attracted to the water and the tails repel the water. The membrane is fluid because it is constantly moving.

Fluidity of the Phospholipid Bilayer Fluidity of the Phospholipid Bilayer can be affected by….. Length of the fatty acid tail: The longer the tails are, the more contact that they’ll have with each other which will cause the membrane to be rigid Temperature: It is crucial that the temperature of the membrane is able to be maintained in order to function properly. If it is too cold the membrane will become stiff, but if it’s too warm the membrane will become very fluid-like Degree of Saturation in the fatty acid tails: Unsaturated tails are bent which makes them ideal for being able to slide past each other. When there are too many saturated fat (straight tails), they are more likely to be intertwined with each other causing rigidness

Crossing Plasma Membrane (A) Passive Transport: Moving from an area of high concentration to low concentration Active Transport: Moving against the concentration gradient from an area of low concentration to an area of high concentration. Channel Proteins: Are specialized proteins that allow for movement across the membrane These are all important because lipid based molecules are hydrophobic so they can’t transport across the membrane without help.

Endocytosis Endocytosis: The process in which a substance passes through the plasma membrane into the cell Three types of endocytosis are phagocytosis, pinocytosis, and receptor mediated endocytosis Phagocytosis: The membrane binds to an item and engulfs it. This is most common in the immune system when the body is trying to destroy bacteria or viruses Pinocytosis: The transport of a fluid into the cell Receptor mediated Endocytosis: Receptors on the cell wall will bind to specific substances which allows the substance to pass through the cell membrane

Endocytosis Phagocytosis Pinocytosis Receptor Mediated

Exocytosis (A) Exocytosis is the reverse of endocytosis It is when material from a cell is transported out by the plasma membrane. It helps the cell by getting rid of unwanted materials and waste that has built up in the cell. It can also help by detecting disease causing bacteria.

Conclusion Plasma membrane is an important division because it is the way that material is transported in and out of the cell. Without it, waste materials could just build up inside the cell and kill it. Or the cell would be missing the important proteins it needs to be able to grow and divide.

Works Cited Crossing Membranes. (n.d.). Retrieved December 06, 2017, from https://alevelnotes.com/Crossing- Membranes/142 Endocytosis and Exocytosis. (n.d.). Retrieved December 06, 2017, from https://oli.cmu.edu/jcourse/workbook/activity/page?context=0baa013680020ca600c2dd2f878d3284 Fluid mosaic model: cell membranes article (article). (n.d.). Retrieved December 06, 2017, from https://www.khanacademy.org/test-prep/mcat/cells/cell-membrane-overview/a/fluid-mosaic-model-cell- membranes-article E. (n.d.). Bilayer structure. Retrieved December 06, 2017, from http://blog.cambridgecoaching.com/what-is- the-phospholipid-bilayer-and-what-determines-its-fluidity