2. Content
● Phospholipids: chemical structure and functions by
Shweta Kumaii (05)
● Phospholipids: subclasses by Naman Sinha (06)
● Lipid bilayer: structure, functions, and formation by
Pieina (08)
● Lipid bilayer: properties, and various similar models
by Shatakshi Bisht (07)
4. ● Phospholipids are one of the methods the body uses to control the flow of molecules, by forming
a bilayer that controls the flow of water loving and water fearing molecules.
● Most abundant type of conjugated lipid. Consisting of :
○ Two fatty acids (CH3(CH2)nCOOH)
○ A phosphate group (PO 3-)
4
○ A Glycerol molecule (CH2OH-CHOH-CH2OH)
● Major constituent of cell membrane.
of the
○ Amphiphatic in nature.
○ Anchor proteins within in cell membrane.
○ Components of bile and lipoproteins.
○ Regulate cellular functions & integrity
membranes of organelles.
Source: https://www.toppr.com/ask/question/describe-the-structure-of-phospholipids-how-are-they-arranged-in/
What are phospholipid ?
6. ● The glycerol backbone of the phospholipid molecule consists of
three carbon atoms connected together. Each carbon atom is bonded
to one oxygen atom, and the remaining bonds are to hydrogen atoms.
This is the same backbone that is found in mono, di, and
triglycerides.
● The fatty acid chain is simply any fatty acid group. A fatty acid group
starts with a carbon double bonded to an oxygen atom and then a
chain of carbon molecules bonded to each other.
● The phosphate group is a phosphorus atom bonded to four oxygen
atoms. One of these oxygen atoms is attached to the glycerol
backbone. Another is an oxygen-hydrogen group (OH or alcohol
group). Another is double bonded to the phosphorous. The final
oxygen atom has a negative charge which attracts another group (this
group differs in different types of phospholipids).such as
serine,choline,Ethanolamine,Inositol,glycero.- Giving a diverse set of
phospholipids.
Source:https://study.com/learn/lesson/phospholipid-structure-function.html#:~:text=The%20phospholipid%20structure%2C%20which%20consists,bonds%20are%20to%20hyd
rogen%20atoms.
Phospholipid structure, which consists of
glycerol backbone, a fatty acid chain, and
a phosphate group.
CHEMICAL STRUCTURE
7. A phospholipid bilayer is formed due to phospholipid stacking tail to tail
PHOSPHOLIPID BILAYER
● The phospholipid bilayer is where two layers of phospholipids are stacked together. This is
what forms the protective barrier for the cell. This stack has hydrophilic heads on the
outside, like the bread of the sandwich, and the hydrophobic tails on the inside.
Image source: https://en.m.wikiversity.org/wiki/File:Bilayer_scheme.svg
8. Functions of Phospholipids
● Cell Membrane Structure:
● Form the fundamental structural component of cell membranes.
● Create a lipid bilayer that separates the cell's interior from the external environment.
● Selective Permeability:
● Regulate the passage of molecules in and out of cells.
● Enable selective transport of ions, nutrients, and waste products.
● Signal Transduction:
● Participate in cell signaling pathways.
● Act as secondary messengers in signal cascades.
● Cell Recognition:
● Important for cell adhesion and recognition.
● Play a key role in immune responses and tissue-specific interactions.
● Additional Roles:
● Formation of lipid rafts for specialized membrane microdomains.
● Energy storage in cells with energy released upon ester bond hydrolysis.
● Utilization in drug delivery systems, such as liposomes.
● Commonly used as emulsifiers in the food industry.
● Found in skincare products for skin hydration and as a protective barrier.
9. APPLICATIONS
Phospholipids, which are a fundamental component of cell membranes, have various real-life applications across
different fields. Here are some notable applications:
1. Drug Delivery Systems: Phospholipids are used to create liposomes, which are tiny vesicles formed from lipid
bilayers. Liposomes can encapsulate drugs, allowing for controlled and targeted drug delivery. This is especially
useful in cancer treatment, as it can reduce the side effects of chemotherapy.
2. Food Industry: Phospholipids are used as emulsifiers in the food industry to improve the stability and texture of
products like mayonnaise, salad dressings, and chocolate. They help mix ingredients that would naturally
separate, such as oil and water.
3. Pharmaceuticals: Phospholipids are utilized in pharmaceutical formulations to improve the solubility and
bioavailability of poorly water-soluble drugs. This enhances drug absorption and effectiveness.
4. Cosmetics and Skincare: Phospholipids are found in many cosmetics and skincare products due to their
moisturizing and emollient properties. They help maintain skin hydration and create a barrier to protect against
external factors.
5. Biotechnology: Phospholipids are used in biotechnology for the formation of liposomes and lipid nanoparticles,
which are employed in drug delivery, gene therapy, and vaccine development.
These applications showcase the versatility of phospholipids in various industries, from healthcare to food production
and scientific research. Their unique properties make them valuable in creating diverse products and technologies.
11. 1. Glycerophospholipids
A. Major lipid that occur in biological membrane.
B. Consist of glycerols 3-phosphate esterified at its R1 and R2 with fatty
acids.
C. Usually R1 Contain saturated fatty acid.R2 contain unsaturated fatty
acid.
i) PhosphatidicAcid
A. Simple phospholipid.
B. Phosphatidic acid is an intermediate in synthesis of triacylglycerols and
phospholipid.
● Lecithin
A. Most abundant group of phosphatidic in cell membrane.
B. Chemically lecithin in phosphatidic acid with choline as the bags.
14. ● Cephaline
A. Enthanolamine is the nitrogenous base present in cephaline.
B. This lecithin 2 cephaline differ with regard to the base.
ii) Phosphatidylinositol
A. Important component of cell membrane.
B. Action of certain hormones (e.g oxytocin,vasopressin) is mediated through
PI
C. In response to hormonal action PI is cleaved to diacyloglycerol and inositol
triphosphate.
D. Both these compounds act as second messengers for hormonal action.
iii) Phosphatidylserine
A. Amino acid serine is present in the group of Glycerophospholipid.
iv) Plasmalogens
A. When fatty acid is attached by an ether linkage at C1 of glycerol in
the glycerophospholipid resultant compound is plasmalogen.
17. v) Cardiolipin
A. Consist of 2 molecules of 2 molecules of phosphatidic acid held by an
additional glycerol through phosphate group.
B. Cardiolipin is the only phosphoglyceride that possess antigenic properties.
vi) Sphingomycelins
A. Sphingosine is an amino alcohol present in sphingomycelins.
B. Do not contain glycerol.
C. Important constituents of myeline and are found in good quantity in brain
and nervous tissue.
19. Lipid Bilayer Formation :
Chemical Structure and Functions in cell membrane
Presented by : Prerna
(08)
20. Importance OF Cell
Membrane
The cell membrane is an essential
component of cell’s overall function. The
cell membrane provides an important
barrier that protects the cell's interior. The
cell membrane also keeps molecules like
proteins, carbohydrates, and nucleic acids
inside the cell. It also keeps toxic materials
like ions, alkalis, and acids outside the cell.
The cell membrane is also essential for the
regulation of molecule transport into and
out of the cell.
Role As A Selective Barrier For Cell
The cell membrane also known as plasma membrane, is found in all cells and separates the
interior of the cell from the outside environment. The cell membrane consists of lipid bilayer i.e.
semipermeable. The cell membrane regulates the transport of materials entering and exiting the
cells.
Selective Permeability:The cell membrane is
selectively permeable, meaning it allows
specific substances to enter or exit the cell
while restricting others.This selectivity is
essential for maintaining the cell's internal
conditions and regulating the exchange of
molecules.
Role as a Selectively Permeable Membrane:
• Controlled Transport
• Active Transport
• Passive Transport
• Osmosis
• Homeostasis
Cell Membrane
21. Role of Lipids in
cell membrane
LIPID
Lipids are fatty compounds that perform a variety of functions in
your body. Lipids play a crucial role in the cell membrane. The cell
membrane is primarily composed of a lipid bilayer, which consists
of various lipid molecules. They're part of your cell membranes and
help control what goes in and out of your cells. They help with
moving and storing energy, absorbing vitamins and
making hormones.
ROLE OF LIPID IN CELL MEMBRANE
Structural Component: Lipids are the primary structural elements of the cell
membrane. Phospholipids, in particular, are the most abundant lipid
molecules in the bilayer.They form the basic framework of the membrane.
Barrier Function: Lipids create a barrier that separates the cell's internal
environment from the external surroundings.
Fluidity and Flexibility: Lipids provide fluidity to the cell membrane. The
hydrophobic tails of phospholipids can move laterally within the bilayer,
allowing the membrane to remain dynamic and adaptable.
Energy Storage: Some lipids, like triacylglycerols, are stored in the cell
membrane and serve as an energy reservoir.When needed, these lipids
can be hydrolyzed to release energy for cellular processes.
22. Lipid bilayer formation is a fundamental process in cell biology. Here's an overview of how lipid bilayers
are formed:
Lipid Molecules: Lipid bilayers consist primarily of phospholipid molecules. Phospholipids have a
hydrophilic (water-attracting) head and two hydrophobic (water-repelling) tails.
Hydrophilic-Hydrophobic Interaction: When phospholipids are placed in an aqueous environment, their
hydrophilic heads orient themselves towards the surrounding water, while their hydrophobic tails cluster
together away from the water.
Bilayer Formation: The hydrophilic heads face outward, interacting with water, while the hydrophobic tails
are shielded from water within the bilayer.
Self-Assembling Property: Phospholipids self-assemble to form a continuous, double-layered structure.
This bilayer is often referred to as the lipid bilayer or cell membrane.
Fluid Mosaic Model: The lipid bilayer is dynamic, allowing for lateral movement of lipids and proteins
within it.This dynamic nature is described by the fluid mosaic model.
Membrane Proteins: Proteins are embedded in the lipid bilayer, contributing to its structure and function.
These membrane proteins have diverse roles, including transport, signaling, and cell adhesion.
Lipid bilayer formation
23. Cholesterol: Cholesterol, a type of lipid, is interspersed within the bilayer. Cholesterol molecules help
regulate the fluidity of the membrane. They make the membrane more stable and less permeable to
small, uncharged molecules.
The lipid bilayer is the barrier that keeps ions,
proteins and other molecules where they are
needed and prevents them from diffusing into areas
where they should not be, and identification ,
communication, regulation of solute exchange
through the membrane, and isolation of the
cytopla.sm from the external environment.
24. Lipids are a diverse group of organic molecules that are insoluble in water but soluble in nonpolar
solvents like benzene and ether.. The basic components of many lipids are fatty acids and glycerol.
2. Glycerol : Glycerol is a three-carbon alcohol
with a hydroxyl group (-OH) attached to each
carbon atom. It serves as the backbone of many
lipids, especially triglycerides.
Structure of Glycerol:
CH2-OH
|
CH-OH
|
CH2-OH
1. Fatty Acids: Fatty acids are the building blocks of
most lipids.They consist of a long hydrocarbon
chain (hydrophobic "tail") with a carboxyl group
(-COOH) at one end (hydrophilic "head").The
carbon atoms in the chain are typically numbered
starting from the carbon adjacent to the carboxyl
group.
CHEMICAL STRUCTURE OF LIPID
26. ● Phospholipids are amphiphilic.
● The presence of membrane proteins in the bilayer
facilitates their transport across the impermeable
barrier.
● The characteristic architecture of the lipid bilayer is
stabilized by the hydrophobic and Van der Waals
interactions between the lipid chains.
● Phospholipids in the lipid bilayer show either
rotation or lateral movement in one bilayer, while
transverse movement between bilayers in a “flip-
flop” manner.
27. ● Membrane fluidity is increased
by phosphoglycerides while
decreased by sphingolipids and
cholesterol
● Phospholipids are structural
units of biological membranes
and facilitate anchoring the
membrane proteins.
● Phospholipids exhibit
asymmetrical distribution in the
two leaflets of the bilayer.
29. Sandwich Model
● The Davson–Danielli model was a model of the
plasma membrane of a cell, proposed in 1935 by
Hugh Davson and James Danielli.
● The model describes a phospholipid bilayer that
lies between two layers of globular proteins and it
is trilaminar and lipoproteinous.
● It was the first model that attempted to describe the
position of proteins within the lipid bilayer found
in membranes.
● Danielli and Davson proposed a model whereby
two layers of protein flanked a central
phospholipid bilayer.
● The model was also described as a ‘lipo-protein
sandwich’, as the lipid layer was sandwiched
between two protein layers.
30. Unit Membrane Model
● Robertson proposed the unit membrane model of
the plasma membrane in 1959A.D.
● The Biomembrane model proposed by Robertson
stated that these are made up of three layers and
out of these three layers, two are protein layers and
one is a phospholipid layer.
● Both the Danielli and Davson model and
Robertson’s model of the unit membrane are
collectively called lamellar models.
● Although each of these membranes may serve
different functions, they all share two common
properties: they exhibit both a selective
permeability to lipid solvents as well as a high
electrical resistance.
31. Fluid Mosaic Model
● The fluid mosaic model describes the structure of
the plasma membrane as a mosaic of components
including phospholipids, cholesterol, proteins, and
carbohydrates, that gives the membrane a fluid
character.
● The combined evidence from electron microscopy
and studies of chemical composition, as well as
physical studies of permeability and the motion of
individual protein and lipid molecules within
membranes, led to development of the fluid mosaic
model for the structure of biological membranes.
● Individual phospholipids can move laterally and
spin within the plane of membrane, giving it a
fluid-like consistency similar to olive oil.
