Answer Learning Outcome / Chapter 4 Membrane Structure And Function

Chapter 4 Membrane Structure and Function
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Chapter 4 Membrane Structure and Function
The fluid-mosaic model of membrane structure is the combination of protein, phospholipids, and steroids. The cell membrane of the plasma membrane separates the internal environment from the external environment. To achieve this function, the plasma membrane regulates the flow of molecules insides and outside of the cell. This process is critical as it helps the cell and the entire organism to maintain a steady state of the internal environment or homeostasis (Mader & Windelspecht, 2017). The plasma membrane is made up of phospholipids, a type of lipids that portrays both hydrophilic and hydrophilic properties. The cell membrane is comprised of numerous proteins where the protein molecules are either wholly or partially embedded. The proteins are always scattered either outside or within the membrane and can be either partially or wholly embedded in a phospholipid bilayer. The two types of proteins, integral proteins and peripheral proteins span the membrane, with the proteins in the membrane forming a mosaic pattern. The combination of steroids, phospholipids, and proteins is known as the fluid-mosaic model.
The diverse roles of proteins in membranes include structural functions and can take part in signalling pathways. For instance, integral proteins determine the specific function of a membrane and are of different types, including carrier proteins, channel proteins, cell recognition proteins, enzymatic proteins, and receptor proteins (Mader & Windelspecht, 2017). Channel proteins are largely involved in the passage of substances in and out of the membrane, and while carrier proteins function similar to channel proteins, they combine with molecules to facilitate their movement across the cell membrane. Cell recognition proteins are primarily glycoproteins, which help the body recognize invading pathogens, and receptor proteins have unique shapes that facilitate binding of molecules to their surfaces. Finally, enzymatic proteins are involved in metabolism especially the integral proteins of the electron transport chain.
The cell membrane is selectively permeable because the life of a living cell depends on the maintenance of its normal composition. The plasma membrane controls the passage of molecules in and out of the cell in a selective fashion. This implies that certain substances can freely move across the membrane but others cannot. Usually, small and non-charged molecules such as oxygen, carbon dioxide alcohol and glycerol can freely move across the membrane while polar molecules such as water will not be allowed to freely move across the ce...