Biological Membrane and transport
When it comes to Biochemistry, it is really important to know about biological membranes and its transportation mechanisms. So, here we go….
What is Biological Membrane?
The membrane can be simply
defined as a closed space that comprises of certain components. So, a
biological membrane is a closed surface or a boundary that consists of cell-
organelles in an aqueous environment. They also contain proteins that are
embedded on the membrane, which reacts with the components that are present on
the membrane and Create complex reaction sequences.
These membranes are semi-
permeable to the polar solutes and they help in removing toxic substances and
also promote exchange of nutrients and other substances.
They also exhibit endocytosis
and exocytosis.
They not only act as barriers,
but they also promote exchange of ions, organic solutes and also help the
receptors in the alteration at the molecular level in the cell.
These membranes help in
organizing the process of synthesizing lipids and proteins that are necessary
for the accomplishment of biological processes such as energy production and
transportation in mitochondria and chloroplasts.
Since, the membranes are two-
dimensional, the enzyme- catalysed processes are organized very
efficiently.
A biological membrane generally consists if Endoplasmic Reticulum, Nuclear membrane, enzymes, aqueous solution and other granules.
Structure and Composition
While we are
studying about the structure and Composition, we need to clearly understand
that, few components such as lipids and proteins are common to all kind of biological
membranes. They may also exist as a part of glycolipids and glycoproteins.
A biological
membrane consists of neurons that have sheath like structure, that is present
as bundle over the cell. The myelin sheath is made up of lipids that helps them
in providing electrical insulation while the membrane of mitochondria and
chloroplasts and other components that are involved in enzyme – catalysed
reactions consist more amount of Protein.
Cells have
certain strategies to control their lipid production and the distribution
varies from each cell, each tissue, each organism. For eg:- Plasma membrane
consists of cholesterol and sphingolipids in a large amount while they lack
cardiolipin. On the other hand, mitochondrial membranes consist of Lower amount
of cholesterol and sphingolipids, but contain a vast amount of
phosphatidylglycerol and cardiolipin.
When we
come to protein composition, it can be seen that, they are covalently connected
to oligosaccharides. For eg:- Glycophorin, one of the membrane of red- blood
cells, 60% of the mass consists of oligosaccharides, that is covalently
attached to specific amino acid residues. The sugar portion that are present on
the surface of the glycoproteins, play a major role in the orientation of the
membrane, binding of ligands to glycoprotein surface receptors.
Membrane
proteins that are attached by a covalent bond to one or more lipids, serve as
hydrophobic anchors, that hold the proteins to the membranes.
In the upcoming articles, we will see on properties of the biological membrane and lipid bilayer.
0 Comments