Membrane contact site
Encyclopedia
Membrane contact sites are areas within a cell
where the membranes of two organelle
s are arranged in close proximity (not to be confused with cell junction
s between the cells). These sites are thought to be important in the transport of small molecules such as lipid
s between organelles, and offer an alternative to the classical mechanism of lipid transport through vesicles
. Membrane contact sites may be particularly important in the function of the endoplasmic reticulum
, since this is the major site of lipid synthesis within cells. These structures can form between the ER and many organelles, including mitochondria, peroxisomes, Golgi, peroxisomes, lysosomes and the plasma membrane. They can also form between other organelles, such as between the cell nucleus
and the vacuole
in yeast..
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
where the membranes of two organelle
Organelle
In cell biology, an organelle is a specialized subunit within a cell that has a specific function, and is usually separately enclosed within its own lipid bilayer....
s are arranged in close proximity (not to be confused with cell junction
Cell junction
A cell junction is a type of structure that exists within the tissue of a some multicellular organism . Cell junctions consist of protein complexes and provide contact between neighbouring cells or between a cell and the extracellular matrix...
s between the cells). These sites are thought to be important in the transport of small molecules such as lipid
Lipid
Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...
s between organelles, and offer an alternative to the classical mechanism of lipid transport through vesicles
Vesicle (biology)
A vesicle is a bubble of liquid within another liquid, a supramolecular assembly made up of many different molecules. More technically, a vesicle is a small membrane-enclosed sack that can store or transport substances. Vesicles can form naturally because of the properties of lipid membranes , or...
. Membrane contact sites may be particularly important in the function of the endoplasmic reticulum
Endoplasmic reticulum
The endoplasmic reticulum is an organelle of cells in eukaryotic organisms that forms an interconnected network of tubules, vesicles, and cisternae...
, since this is the major site of lipid synthesis within cells. These structures can form between the ER and many organelles, including mitochondria, peroxisomes, Golgi, peroxisomes, lysosomes and the plasma membrane. They can also form between other organelles, such as between the cell nucleus
Cell nucleus
In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...
and the vacuole
Vacuole
A vacuole is a membrane-bound organelle which is present in all plant and fungal cells and some protist, animal and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic molecules including enzymes in solution, though in certain...
in yeast..