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BIOL 1121 Unit 3 written assignment
Biology 1 for Health Studies Majors (BIOL 1121)
University of the People
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Unit 3 -Written Assignment
Name withheld for peer grading
University of the People BIOL 1121 - AY2021-T Dr. Yih Woei Fridell September 2020
Structure of a eukaryotic plasma membrane The plasma membrane consists of a phospholipid (i. a lipid molecule that consists of two fatty acid chains and one phosphate group) bilayer that’s embedded with protein. It helps in separating the cells inner contents from the external environment. It regulates the movement of organic molecules and ions in and out of the cell. Also, wastes like carbon dioxide passes through this plasma membrane to leave the cell. Microvilli are fingerlike projections that are present in cells that specialize in absorption. "The fluid mosaic model describes the plasma membrane structure as a mosaic of components—including phospholipids, cholesterol, proteins, and carbohydrates— that gives the membrane a fluid character." (Clark, M., Choi, J. & Douglas, M. 2020).
Proteins are the second major component of the plasma membrane (first being the phospholipid molecules). According to Clark, M., Choi, J. & Douglas, M. (2020)., Integral proteins integrates fully into the membrane and their hydrophobic membrane-spanning region reacts with hydrophobic area of the phospholipid bilayer. Other complex proteins (consisting of 12 or less segments which are folded as well as embedded in the plasma membrane) consists of a single hydrophilic region and one or more than one hydrophobic region. This is because the regions of the protein change its direction along with the phospholipids. On the other hand, Peripheral proteins are membrane proteins that temporarily binds to the membrane that they are connected with. These proteins bind the peripheral regions of lipid bilayer to integral proteins. Also, these proteins do not interact with the hydrophobic region of the phospholipid layer. Proteins found in the plasma membrane help the cell to interact with the external environment. They also help in enzyme related activities and inter-cellular joining's.
"Proteins present in the cell membrane helps to move molecules quickly and swiftly. So the movement of molecules which involves the proteins as their helpers is called as facilitated diffusion." (C, R. 2018) The main difference between active and passive transport is that the former require energy for transportation and the later does not. Another main difference between the two is that active transport is fast, uni-directional and molecules move upwards, whereas passive transport is slow, bi-directional and molecules move downwards.
Endocytosis and Exocytosis Endocytosis is the process of bring large molecules into the cell. It is of four types namely, caveolae, micropinocytosis, phagocytosis and receptor-mediated endocytosis. Each of these types corresponds to different pathways for bringing in large molecules in the cell. Example of endocytosis is engulfing bacteria by phagocytes. Exocytosis refers to the fusion of vesicles with plasma membranes to release the cells content to external environment. There are three types of exocytosis namely, phagocytosis, receptor mediated endocytosis and pinocytosis. Example of exocytosis is realizing hormone outside the cell.
Reference:
Clark, M., Choi, J. & Douglas, M. (2020, Jan 18). Biology 2e. Open Stax. Available online openstax/books/biology-2e/pages/preface
Aryal, S. (2019). Membrane Carbohydrate. Retrieved from: microbenotes/membrane-carbohydrate/
Biology Online (n). Active Transport. Retrieved from: biologyonline/dictionary/active-transport
C, R. (2018). Difference Between Active and Passive Transport. Retrieved from: biodifferences/difference-between-active-and-passive-transport.html
BIOL 1121 Unit 3 written assignment
Course: Biology 1 for Health Studies Majors (BIOL 1121)
University: University of the People
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