Membrane Transport: Cell Membrane Transport and Signal TransductionAuthor(s): Dr. Garima Peeters
Specialized cell functions can be localized, contained, and independently regulated by organelles. Membranes that are selectively permeable are frequently used to achieve this separation. These membranes allow for the control of molecular transport, signalling between compartments, and the confinement of factors that cause stress. Here, we examine the cell's various membrane systems and their functions: the endoplasmic reticulum membrane, the plasma membrane, and the nucleus, the cell's chromatin storage and regulatory hub. Ions, metabolites, proteins, and messenger RNA can be moved to and from the nucleus through nuclear pores. Translocation across the nuclear envelope also alters the activity of transcription factors and signalling molecules. The nuclear pores, Ran-GTP activity, and the nuclear lamina may be responsible for regulating many of these processes, which require "active transportation" against a concentration gradient. We also discuss how mechanical signals are carried from outside the cell into the nucleus through integrins, the cytoskeleton, and the "linker of nucleo- and cyto-skeletal" (LINC) complex, which spans the nuclear envelope. Cells must respond to a combination of biochemical and physical inputs. Cells are able to maintain homeostasis within functional tissue through regulation and response to internal and external stresses and signals. The ability of a membrane to precisely regulate the concentration of solutes in the inside and outside aqueous compartments that bathe it is essential for life. The solutes that enter and leave a cell are controlled by the membrane. Complex interactions between membrane lipids, proteins, and carbohydrates control Tran’s membrane transport. This chapter examines how the membrane performs these functions.