Structure and Composition of Cell Membrane
Despite differences in structure and function, all living cells in multicellular organisms are surrounded by a cell membrane. Just like the outer layer of the skin separates the body from its environment similarly, the cell membrane, also known as 'plasma membrane,' separates the inner content from its exterior environment.
Cell Membrane
The cell membrane is known by different names like plasma membrane or cytoplasmic membrane, or biological membrane. The term "cell membrane" was first introduced by C. Nageli and C. Cramer in the year 1855. Later on, in 1931, the term "plasmalemma" for cell membrane was given by J. Plowe. The cell membrane separates the cell's internal environment from the extracellular space. This separation allows the protection of cells from their environment.
Prokaryotes vs Eukaryotes
The cell is defined as the basic structural and functional unit of life. The cell membrane bounds it. It is capable of independent existence.
The following image is based on real results from an influential experiment in cell biology. This experiment studied the role of the proteins Ran and importin in nuclear protein transport. The experiment used flourescently-labeled proteins containing a nuclear localization sequence (the "substrate"). Ran, importin, and GTP were either present or absent, as indicated in the figure. Cells were exposed to these different conditions and then analyzed by fluorescence microscopy.
Circles are the cells' nuclei. Very light circles are the nuclei without the substrate attached.
Study the figure below and then answer the questions that follow.
1. What actions does Ran perform by itself?
2. What actions does importin perform by itself?
3. How do Ran and importin act together in the nuclear import of protein?
4. Why is GTP required?
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