Plasma Membranes
DEFINE THE PLASMA MEMBRANE
The plasma membrane is defined as the boundary between the cells and its environment.
According to Roush.R. Fowler.S. and Wise.J. a cell’s plasma membrane defines the boundary of
the cell and determines the nature of its contact with the environment. Plasma membranes
enclose the borders of cells, but rather than being a static bag, they are dynamic and constantly in
flux. The plasma membrane must be sufficiently flexible to allow certain cells, such as red blood
cells and white blood cells, to change shape as they pass through narrow capillaries. The plasma
membrane is also known as the cell membrane or cytoplasmic membrane.
The modern understanding of plasma membrane is referred to as the fluid mosaic model says
College Biology by Hardy.M. . The plasma membrane is composed of a bilayer of phospholipids
with their hydrophobic, fatty acid tails in contact with each other. The landscape of the
membrane is studded with proteins, some of which span the membrane. Carbohydrates are
attached to some of the proteins and lipids on the outward facing surface of the membrane,
forming complexes that function to identify the cells to other cells. The fluid nature of the
membrane is due to temperature, the configuration of fatty acid tails, the presence of cholesterol
embedded in the membrane and the mosaic nature of the proteins and protein-carbohydrates
which are not firmly fixed in a place. Plasma membranes enclose and define the bodies, the
borders of the cells, they are dynamic and constantly in flux.
STRUCTURE OF THE PLASMA MEMBRANE
The plasma membrane is made up of both lipids and proteins. The fundamental structure of the
membrane is the phospholipid bilayer, which forms a stable barrier between two aqueous
compartments. Referencing Jones.M.,Fosberg.R.,Gregory.J. and Taylor.D. , they state that the
phospholipid bilayer is visible using the electron microscope at a very high magnification at least
x100 000. The plasma membrane is made up primarily of a bilayer of phospholipids with
embedded proteins, carbohydrates, glycolipids, and glycoproteins, and, in animal cells,
cholesterol. The amount of cholesterol in animal plasma membranes regulates the fluidity of the
membrane and changes based on the temperature of the cell’s environment. In other words,
cholesterol acts as antifreeze in the cell membrane and is more abundant in animals that live in
cold climates according to Roush.R. Fowler.S. and Wise.J.
In 1972, S. J. Singer and Garth L. Nicolson proposed a new model of the plasma membrane that,
compared to earlier understanding, better explained both microscopic observations and the
function of the plasma membrane. This was called the fluid mosaic model. The model has
evolved somewhat over time, but still best accounts for the structure and functions of the plasma
membrane as we now understand them. They put forward the theory of the fluid mosaic model of
DEFINE THE PLASMA MEMBRANE
The plasma membrane is defined as the boundary between the cells and its environment.
According to Roush.R. Fowler.S. and Wise.J. a cell’s plasma membrane defines the boundary of
the cell and determines the nature of its contact with the environment. Plasma membranes
enclose the borders of cells, but rather than being a static bag, they are dynamic and constantly in
flux. The plasma membrane must be sufficiently flexible to allow certain cells, such as red blood
cells and white blood cells, to change shape as they pass through narrow capillaries. The plasma
membrane is also known as the cell membrane or cytoplasmic membrane.
The modern understanding of plasma membrane is referred to as the fluid mosaic model says
College Biology by Hardy.M. . The plasma membrane is composed of a bilayer of phospholipids
with their hydrophobic, fatty acid tails in contact with each other. The landscape of the
membrane is studded with proteins, some of which span the membrane. Carbohydrates are
attached to some of the proteins and lipids on the outward facing surface of the membrane,
forming complexes that function to identify the cells to other cells. The fluid nature of the
membrane is due to temperature, the configuration of fatty acid tails, the presence of cholesterol
embedded in the membrane and the mosaic nature of the proteins and protein-carbohydrates
which are not firmly fixed in a place. Plasma membranes enclose and define the bodies, the
borders of the cells, they are dynamic and constantly in flux.
STRUCTURE OF THE PLASMA MEMBRANE
The plasma membrane is made up of both lipids and proteins. The fundamental structure of the
membrane is the phospholipid bilayer, which forms a stable barrier between two aqueous
compartments. Referencing Jones.M.,Fosberg.R.,Gregory.J. and Taylor.D. , they state that the
phospholipid bilayer is visible using the electron microscope at a very high magnification at least
x100 000. The plasma membrane is made up primarily of a bilayer of phospholipids with
embedded proteins, carbohydrates, glycolipids, and glycoproteins, and, in animal cells,
cholesterol. The amount of cholesterol in animal plasma membranes regulates the fluidity of the
membrane and changes based on the temperature of the cell’s environment. In other words,
cholesterol acts as antifreeze in the cell membrane and is more abundant in animals that live in
cold climates according to Roush.R. Fowler.S. and Wise.J.
In 1972, S. J. Singer and Garth L. Nicolson proposed a new model of the plasma membrane that,
compared to earlier understanding, better explained both microscopic observations and the
function of the plasma membrane. This was called the fluid mosaic model. The model has
evolved somewhat over time, but still best accounts for the structure and functions of the plasma
membrane as we now understand them. They put forward the theory of the fluid mosaic model of
