Structure and Function of the Eukaryotic Plasma Membrane

Structure and Function of the Eukaryotic Plasma Membrane

The eukaryotic plasma membrane structure comprises proteins and a bilayer of lipids. It also comprises a small percentage of carbohydrates, which combine with glycolipids and glycoproteins to form glycocalyx. Phospholipids form a double-layer membrane because their molecules have charged (polar) heads and uncharged (nonpolar) tails. The polar heads are hydrophilic (attracted to water molecules) and are exposed to the cell’s extracellular and intracellular aqueous fluids. The nonpolar tails are hydrophobic.

Macromolecules of the plasma membrane include lipids and proteins. Lipids consist of phospholipids and cholesterol. Phospholipids assemble around damaged sites for repair, while cholesterol provides stability to the plasma membrane by limiting the movement of lipids. Additionally, proteins are classified into integral and peripheral proteins. They function as marker molecules allowing cells to identify other cells or molecules; attachment proteins anchoring cells to other cells or to other molecules; transport proteins allowing movement of ions or molecules across the plasma membrane; receptor proteins providing binding sites for chemical signals in the extracellular fluid and as enzymes catalyzing chemical reactions (Vanputte et al., 2020).

The plasma membrane is selectively permeable and allows entry of specific substances only through different transport mechanisms depending on the chemical characteristics of the substances. These mechanisms include simple diffusion, osmosis, facilitated diffusion, active transport, and coupled transport. Simple diffusion is the movement of molecules from high to low-concentration regions, while osmosis is the diffusion of water molecules through a selectively permeable membrane from high to low-concentrated regions. Facilitated diffusion is the movement of substances from highly to lowly concentrated areas through plasma membrane pores with the help of carrier proteins, while active transport uses ATP-powered pumps to move substances from low to high regions of concentration across the plasma membrane. Coupled transport is an ion-driven secondary active transport.

Endocytosis requires ATP and involves transporting substances into the cell through a vesicle formed by the plasma membrane around these substances. On the other hand, exocytosis involves packaging manufactured materials by the cell into secretory vesicles and the fusion of these vesicles to the plasma membrane to release the materials outside the cell, utilizing ATP.

To conclude, the eukaryotic plasma membrane has a flexible and stable structure and a chemical characteristic that helps accomplish its essential functions, such as covering the entire cell, repairing damages, selective transport of substances, and helping cells identify other cells or molecules.

References

Vanputte, C., Regan, J., Russo, A., Seeley, R., Stephens, T., and Tate, P. (2020). Seeley’s Anatomy & Physiology. 12th ed. New York: McGraw-Hill Education.

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Membranes are essential components of all cells.
• Briefly describe the structure of a eukaryotic plasma membrane, identifying at least two component macromolecules and describing what their basic function is within the membrane.

The plasma membrane protects the integrity of the cell’s interior by allowing certain substances in while keeping others out.
• Summarize the manner in which small molecules are permitted to pass through the membrane, ensuring you explain the difference between passive, facilitated, active, and coupled transport by comparing and contrasting them.
• Finally, explain the difference between endocytosis and exocytosis and provide an example of a molecule (remembering to state its function) that is transferred using this method.
Written Assignment Requirements
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