Homeoviscous adaptation
Encyclopedia
The maintenance of proper cell membrane
fluidity is of critical importance for the function and integrity of the cell
, essential for the mobility and function of embedded proteins and lipids, diffusion of proteins and other molecules laterally across the membrane for signaling reactions, and proper separation of membranes during cell division
. A fundamental biophysical determinant of membrane fluidity is the balance between saturated
and unsaturated
fatty acids. Regulating membrane fluidity is especially important in poikilothermic organisms such as bacteria
, fungi, protists, plants, fish
and other ‘cold-blooded
’ animals that cannot regulate their own body temperatures. The general trend is an increase in unsaturated fatty acids at lower growth temperatures and an increase in saturated fatty acids at higher temperatures. This compositional adaptation of membrane lipids, called homeoviscous adaptation, serves to maintain the correct membrane fluidity at the new conditions.
Cell membrane
The cell membrane or plasma membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. It basically protects the cell...
fluidity is of critical importance for the function and integrity of the cell
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....
, essential for the mobility and function of embedded proteins and lipids, diffusion of proteins and other molecules laterally across the membrane for signaling reactions, and proper separation of membranes during cell division
Cell division
Cell division is the process by which a parent cell divides into two or more daughter cells . Cell division is usually a small segment of a larger cell cycle. This type of cell division in eukaryotes is known as mitosis, and leaves the daughter cell capable of dividing again. The corresponding sort...
. A fundamental biophysical determinant of membrane fluidity is the balance between saturated
Saturated fat
Saturated fat is fat that consists of triglycerides containing only saturated fatty acids. Saturated fatty acids have no double bonds between the individual carbon atoms of the fatty acid chain. That is, the chain of carbon atoms is fully "saturated" with hydrogen atoms...
and unsaturated
Saturated fat
Saturated fat is fat that consists of triglycerides containing only saturated fatty acids. Saturated fatty acids have no double bonds between the individual carbon atoms of the fatty acid chain. That is, the chain of carbon atoms is fully "saturated" with hydrogen atoms...
fatty acids. Regulating membrane fluidity is especially important in poikilothermic organisms such as bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
, fungi, protists, plants, fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
and other ‘cold-blooded
Poikilotherm
A poikilotherm is an organism whose internal temperature varies considerably. It is the opposite of a homeotherm, an organism which maintains thermal homeostasis. Usually the variation is a consequence of variation in the ambient environmental temperature...
’ animals that cannot regulate their own body temperatures. The general trend is an increase in unsaturated fatty acids at lower growth temperatures and an increase in saturated fatty acids at higher temperatures. This compositional adaptation of membrane lipids, called homeoviscous adaptation, serves to maintain the correct membrane fluidity at the new conditions.