Biological membrane ke baare mein hai ....

1. TOPIC (IWS) -BIOLOGICAL
MEMBRANE
By- Shashwat Awasthie
265 Group(General Medicine)
Submitted to- Rosa Ma’am
Department of Department of General and
Biological Chemistry.

2. CONTENTS
DEFINITION COMPOSITION
FORMATION FUNCTION

3. DEFINITION
A biological membrane, also known as a biomembrane or a cell
membrane, is a permeable membrane that divides a cell from
its surroundings or generates internal compartments.
Eukaryotic cell membranes are made up of a phospholipid
bilayer containing embedded, integral, and peripheral proteins
that are involved in chemical and ion communication and
transportation.
The existence of an annular lipid shell, composed of lipid
molecules linked closely to the surface of integral membrane
proteins, enables proteins to adapt to the high membrane
fluidity environment of the lipid bilayer.
Mucous membranes, basement membranes, and serous
membranes are examples of isolating tissues created by layers
of cells.

4. A cross-sectional picture of the
configurations that phospholipids in an
aqueous solution can create.

5. COMPOSITION
ASYMMETRY
• The lipid bilayer consists of two layers- an outer leaflet and an inner
leaflet.
• To induce asymmetry between the outer and inner surfaces, the
components of bilayers are dispersed unequally across the two surfaces.
• This asymmetric organization is important for cell functions such as
cell signaling.
• The biological membrane's asymmetry describes the different roles of
the membrane's two leaflets.
• Proteins, lipids, and glycoconjugates facing the lumen of the ER and
Golgi are expressed on the extracellular side of the plasma membrane
during membrane trafficking.
• Enzymes attached to the section of the endoplasmic reticulum
membrane that confronts the cytoplasm produce new phospholipids in
eucaryotic cells.
• Half of the new phospholipid molecules must subsequently be
transported to the opposing monolayer in order for the membrane to
expand evenly as a whole. Flippase enzymes are responsible for the
transfer. Flippases transmit distinct phospholipids preferentially across
the plasma membrane, resulting in a concentration of various kinds in
each monolayer.
• Glycolipids, the lipids with the most prominent and constant
asymmetric distribution in animal cells, are governed by a distinct
process.
LIPIDS
• The Lipids with hydrophobic tails and hydrophilic heads constitute the
biological membrane.
• Hydrophobic tails are hydrocarbon tails whose length and saturation
are crucial in determining the cell's individuality.
• The lipid content of red blood cells (erythrocytes) is unique. Cholesterol
and phospholipids are found in equal amounts in the bilayer of red
blood cells.
• The erythrocyte membrane is essential for blood coagulation.
Phosphatidylserine is found in the bilayer of red blood cells. This is
normally on the membrane's cytoplasmic side. However, during blood
clotting, it is flipped to the outer membrane.

6. PROTEINS
• Membrane proteins have a variety of roles and features, and the
ability to catalyse a range of chemical processes. Integral proteins have
separate domains on both sides of the membranes.
• Integral proteins are strongly linked to the lipid bilayer and are
difficult to separate.
• Only a chemical treatment that disrupts the membrane will cause
them to separate. In contrast to integral proteins, peripheral proteins
have weak connections with the bilayer's surface and can easily
separate from the membrane.
• Peripheral proteins are located on only one face of a membrane and
create membrane asymmetry.
OLIGOSACCHARIDES
• Sugar-containing polymers are known as oligosaccharides. They can
be covalently attached to lipids to create glycolipids or to proteins to
form glycoproteins in the membrane. Glycolipids are sugar-containing
lipid molecules found in membranes.
• The sugar groups of glycolipids are exposed at the cell surface in the
bilayer, allowing them to establish hydrogen bonds.
• Glycolipids are the most severe example of lipid bilayer asymmetry.
Glycolipids play a variety of roles in the biological membrane, the
majority of which are communicative, such as cell recognition and cell-
cell adhesion.
• They play an important role in the immune response and protection.

7. FORMATION
Membrane lipids clump together in
aqueous liquids, forming a
phospholipid bilayer.
The hydrophobic effect, in which
hydrophobic ends come into touch
with each other and are sequestered
away from water, causes aggregation.
This configuration maximises
hydrogen bonding between
hydrophilic heads and water while
reducing unfavourable interaction
between hydrophobic tails and water.
The entropy of the system grows as
the available hydrogen bonding
increases, resulting in a spontaneous
process.

8. FUNCTION
Biological molecules are amphiphilic or amphipathic,
implying they are both hydrophobic and hydrophilic
at the same time. Charged hydrophilic headgroups
interact with polar water in the phospholipid bilayer.
The layers also have hydrophobic tails that interact
with the corresponding layer's hydrophobic tails.
Fatty acids with different lengths make up the
hydrophobic tails. The physical features of lipid
bilayers, such as fluidity, are determined by lipid
interactions, particularly the hydrophobic tails.
Membranes in cells often establish enclosed regions
or compartments in which cells can maintain a
chemical or biological environment distinct from the
surrounding environment. The membrane enclosing
peroxisomes, for example, protects the remainder of
the cell from peroxides, which may be hazardous to
the cell, and the cell membrane divides the cell from
its surroundings.
Most organelles are defined by such membranes and
are called "membrane-bound" organelles.

9. SELECTIVE PERMEABILITY
• A biomembrane's most essential property is that it is a selectively
permeable structure. This implies that whether atoms and molecules
attempting to cross it successfully will be determined by their size,
charge, and other chemical features. For successful isolation of a cell or
organelle from its environment, selective permeability is required.
Generally, small hydrophobic molecules can readily cross phospholipid
bilayers by simple diffusion.
• Particles that are essential for cellular activity but cannot easily diffuse
across a membrane are taken in by a membrane transport protein or
endocytosis, in which the membrane permits a vacuole to attach to it
and push its contents into the cell. Apical, basolateral, presynaptic, and
postsynaptic plasma membranes, membranes of flagella, cilia,
microvillus, filopodia, and lamellipodia, the sarcolemma of muscle cells,
and specialised myelin and dendritic spine membranes of neurons are
all examples of specialised plasma membranes that can separate cells
from their external environment. Caveolae, postsynaptic density,
podosome, invadopodium, desmosome, hemidesmosome, focal
adhesion, and cell junctions are examples of "supramembrane"
structures formed by plasma membranes. The lipid and protein content
of these membranes differs.
• Distinct types- Endosome; smooth and rough endoplasmic reticulum;
sarcoplasmic reticulum; Golgi apparatus; lysosome; mitochondrion
(inner and outer membranes); nucleus (inner and outer membranes);
peroxisome; vacuole; cytoplasmic granules; cell vesicles (phagosomes,
autophagosomes, clathrin-coated vesicles (including synaptosome,
acrosomes, melanosomes, and chromaffin granules).
• Different types of biological membranes have diverse lipid and protein
compositions.
FLUDITY
• Rotations around the bonds of lipid tails keep the hydrophobic core of
the phospholipid bilayer in motion. Bilayer hydrophobic tails flex and
latch together. The hydrophilic head groups, on the other hand, have
reduced mobility and rotation due to hydrogen bonding with water. As
a result, the lipid bilayer's viscosity increases as it gets closer to the
hydrophilic heads.
• When the highly mobile lipids display reduced movement below a
transition temperature, the lipid bilayer loses fluidity and transforms
into a gel-like solid. The length of the hydrocarbon chain and the
saturation of the fatty acids in the lipid bilayer determine the transition
temperature. For bacteria and other cold-blooded animals,
temperature-dependent fluidity is a crucial physiological trait. These
organisms keep their fluidity constant by adjusting the fatty acid
content of their membrane lipids in response to changes in
temperature.
• The presence of the sterol cholesterol in animal cells regulates
membrane fluidity. This molecule is found in particularly high
concentrations in the plasma membrane, where it accounts for around
20% of the membrane's lipids by weight. Because cholesterol molecules
are small and inflexible, they fill the gaps created by the kinks in their
unsaturated hydrocarbon tails between nearby phospholipid molecules.
Cholesterol stiffens the bilayer, making it more rigid and less
permeable in this way.
• Membrane fluidity is critical for all cells for a variety of reasons. It
allows membrane proteins to diffuse quickly in the plane of the bilayer
and interact with one another, which is important in cell signalling, for
example. It allows membrane lipids and proteins to diffuse to different
parts of the cell from the places where they are placed into the bilayer
after production. When a cell splits, it permits membranes to fuse and
mix their molecules, and it guarantees that membrane molecules are
distributed uniformly amongst daughter cells. It's difficult to fathom
how cells might survive, develop, and reproduce if their membranes

10. THANKYOU FOR YOUR ATTENTION
SHASHWAT AWASTHIE