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1. CHEMISTRY OF CELL MEMBRANE ,
RECEPTOR AND DRUG RECEPTOR
INTERACTION
SUBMITTED TO :-
Prof.- Asmita Gajbhiye
Mrs. Swati Rathore
Mrs. Richa Tripathi
PRESEMTED BY:-
Satyam Asati
Y21254022
M.Pharm 2nd SEM
Master of pharmacy
Session – 2021-22
DEPARTMENT OF PHARMACEUTICAL SCIENCES,
Dr. Harisingh gour Vishwavidyalaya sagar M.P.
(A Central University ) -470003

2. INDEX
• Introduction
• Chemical Composition
• Molecular Structure
• Membrane Lipids
• Membrane Proteins
• Membrane Carbohydrates Receptor
• Types Of Receptor
• Drug Receptor Interaction

3. • plasma membrane is also known as cell membrane or cytoplasm
membrane.
• It is the biological membrane, separates interior of the cell from the
outside environment.
• Selective permeable to ions and organic molecules.
• Its basic function is to protect the cell from its surroundings.
• It consists of the phospholipids bilayer with embedded proteins.
• Cell membranes are involved in: cell adhesion, ion conductivity and
cell signaling and serve as the attachment surface for several
extracellular structures.
INTRODUCTION

5. MOLECULAR STRUCTURE
The molecular structure of cell membrane is primarily composed of :-
(a) Membrane Lipids
(b) Membrane Proteins
(c) Membrane Carbohydrate
Cell membranes contain a variety of biological molecules, notably
lipids and proteins.
Some of the proteins and lipids, however, may have oligosaccharides,
covalently attached to them.
The sugar containing sequences of these glycoprotein and glycolipids
also play a role in determining the identity of cells.

6. A) MEMBRANE LIPIDS
• The cell membrane consists of three classes of amphipathic lipids:
phospholipids, glycolipids, and sterols.
• The fatty chains in phospholipids and glycolipids usually contain an
even number of carbon atoms, typically between 16 and 20.
• The entire membrane is held together via non covalent interaction of
hydrophobic tails.
• In animal cells cholesterol is normally found in the irregular spaces
between the hydrophobic tails of the membrane lipids, where it confers
a stiffening and strengthening effect on the membrane.
• The major lipids in the cell membrane is phospholipids.

7. • Each phospholipid molecule has hydrophilic (polar) head and a
hydrophobic (non-polar) tail.
• The hydrophilic heads interact with water while hydrophobic tails remain
away from it and in contact with each other.
• hydrophilic molecules dissolve readily in water because they contain
charged groups or uncharged polar groups that can form either favorable
electrostatic interactions or hydrogen bonds with water molecules.
• Hydrophobic molecules, by contrast, are insoluble in water because almost
all, of their atoms are uncharged and nonpolar and therefore cannot.
• For that reason, lipid molecules spontaneously aggregate to bury their
hydrophobic tails in the interior and expose their hydrophilic heads to
water.
CONTINUE...

8. STRUCTURE:- Phospholipids

9. MEMBRANE PROTEINS
The cell membrane has large content of proteins, typically around 50% of
membrane volume.
Large variety of protein receptors and identification proteins, such as
antigens, are present on the surface of the membrane.
Functions of membrane proteins can also include cell-cell contact, surface
recognition, cytoskeleton contact, signaling, enzymatic activity, or
transporting substances across the membrane.
There are three types of proteins in plasma membrane.
1. Integral proteins.
2. Transmembrane proteins.
3. Peripheral proteins.

10. INTEGRAL PROTEINS
Integral proteins are usually globular and they normally extend in the
interior of the lipid bilayer.
It directly interacts with hydrophobic regions of the bilayer.
The hydrophilic regions of integral proteins are generally exposed to the
cytoplasm and external aqueous phase outside the cell.
They carry out all the functions of the membrane such as transport of
molecules across the membrane, receiving signals from hormones and
establishing cell shape.
Transmembrane proteins are also integral proteins.

11. TRANSMEMBRANE PROTEIN
Transmembrane protein is a type of
integral protein spanning the
entirety of the biological membrane
to which it is permanently attached.
transmembrane proteins span from
one side of a membrane through to
the other side of the membrane.
Many transmembrane proteins
function as gateways to deny or
permit the transport of specific
substances across the biological
membrane.

12. PERIPHERAL MEMBRANE
PROTEINS
Peripheral membrane proteins are proteins that adhere only temporarily to
the biological membrane with which they are associated.
These molecules attach to integral membrane proteins, or penetrate the
peripheral regions of the lipid bilayer.
The reversible attachment of proteins to biological membranes has shown
to regulate cell signaling and many other important cellular events.
Membrane binding may promote rearrangement, dissociation, or
conformational changes within many protein structural domains, resulting
in an activation of their biological activity.

13. MEMBRANE CARBOHYDRATE
Carbohydrates (oligosccharides) in plasma membrane occur as
glycoproteins and glycolipids most of the membrane carbohydrates
are bound to protein molecules.
Carbohydrate chains of all the cell membranes are located
extensively on the exoplasmic surface, i.e. Outside the cell.
Although the functions of membrane carbohydrate seem to be cell
recognition (cell-cell recognition).

14. RECEPTOR

15. RECEPTOR
A receptor is a protein molecule usually found embedded within
the plasma membrane surface of a cell that receives chemical
signals from outside the cell and when such chemical signals bind
to a receptor, they cause some form of cellular/tissue response.
A receptor is a protein molecule in a cell or on the surface of a cell
to which a substance (such as a hormone, a drug, or an antigen) can
bind, causing a change in the activity of that particular cell

16. TYPES OF RECEPTOR
CELL SURFACE
RECEPTOR
ION CHHANEL
RECEPTOR
G-PROTEIN LINKED
RECEPTOR
ENZYME
RECEPTOR
INTRACELLULAR
RECEPTOR
Nuclear receptor

17. ION CHANNEL-LINKED
RECEPTORS
Receptors bind with ligand. (Ex:Nicotinic Receptor)
Open a channel through the membrane that allow
specific ions to pass through
Conformational change in the protein's structure that
allows ions such as Na, Ca, Mg, and H, to pass through.

18. IONOTROPIC RECEPTOR
The first receptor family comprises ligand-gated ion channels
that are responsible for regulation of the flow of ions across cell
membranes.
The activity of these channels is regulated by the binding of a
ligand to the channel. Response to these receptors is very rapid,
having durations of a few milliseconds.
The nicotinic receptor and the gamma-amino butyric acid
(GABA) receptor are important examples of ligand-gated
receptors, the functions of which are modified by numerous
drugs.

19. CONTINUE…
Agonist binding open the channel and causes the depolarization/
hyperpolarization/change in cytosolic ionic composition-action
potential generated and biological response produce.
In this receptor the involvement of 2"d messenger or G-protein are
absent.
Example-Ach ,local anesthetics, general anesthetics etc.
Ach :- Stimulation of the nicotinic receptor by acetylcholine results
in sodium influx.

20. G-PROTEIN LINKED RECEPTOR
It have Seven transmembrane (7TM) α helices coupled to effecter system
(enzyme/channel) through GTP/GDP binding protein called G-proteins
An extracellular domain which G Protein binds to the ligand
(drug/neurotransmitter)
An intracellular domain which couples to G-protein
GPCR Binds with a ligand and activate a membrane protein called a G-
protein
The activated G-protein then interacts with either an ion channel or an
enzyme in the membrane.
Each receptor has its own specific extracellular domain and G-protein-
binding site.
Example : Beta-adrenergic receptor

21. A family of membrane proteins anchored to the
membrane.
Recognize activated GPCR's and pass the message to the
effector system.
Named as G-protein because of their interaction with
guanine nucleotides (GTP/GDP).
Consist of three subunits: alpha, beta and gamma.
Guanine nucleotides bind to the alpha subunit, has
GTPase enzymetic activity.
Functions as a molecular switches. when bind with GTP
they are "on" & when with GDP they are "off".
G- PROTEIN

22. G-PROTEIN SUBUNITS WITH
SECOND MESSENGER

23. ENZYME-LINKED RECEPTORS
These are also known as Catalytic Receptor, is a transmembrane receptor,
where the binding of an extracellular ligand causes enzymatic activity on
the intracellular side.
Cell surface receptors with intracellular domains that are associated with
an enzyme.
Normally have large extracellular and intracellular domains.
When a ligand binds to the extracellular domain, a signal is transferred
through the membrane and activates the enzyme, which eventually leads
to a response.
Example : Tyrosine Kinase receptor, Insulin etc.

25. LIGAND: Any molecule which attaches selectively to particular receptor
AFFINITY: Capability of drug to bind to the receptor and form receptor
complex
INTRINSIC ACTIVITY: Ability of the drug to trigger the
pharmacological response after forming complex
Efficacy: The 'strength' of the agonist-receptor complex in evoking a
response of the tissue
Potency: Amount of drug needed to produce an effect.
DRUG RECEPTOR INTERACTIONS

26. OCCUPATION THEORY, CLARK'S
(1926)
Drugs act on independent binding sites and activate them, resulting in a
biological response that is proportional to the amount of drug-receptor
complex formed
D + R <> DR = RESPONSE
Intensity of pharmacological effect is directly proportional to number of
eceptors occupied
The response ceases when this complex dissociates
Maximal response occurs when all the receptors are occupied at equilibrium

27. PATON'S RATE THEORY (1961)
The response is proportional to the rate of drug-Receptor complex
formation.
Effect is produced by the drug molecules based on the rates of association
and dissociation of drugs to and from the receptors
Antagonists act much more slowly than agonists do and hence the rate of
dissociation is inversely proportional to the potencies of antagonists while
is directly proportional to the agonists
Type of effect is independent of number of receptors rather rate of binding
and release from the receptor.

28. THE INDUCED-FIT THEORY, DANIEL
KOSHLAND (1958)
States that the morphology of the binding site is not necessarily
complementary to the preferred conformation of the ligand
Binding produces a mutual plastic molding of both the ligand and the
receptor as a dynamic process.
The conformational change produced by the mutually induced fit in the
receptor macromolecule is then translated into the biological effect,
eliminating the rigid and obsolete " key and lock" concept
Agonist induces conformational change - response
Antagonist does not induce conformational change – no response

29. THE TWO-STATE (MULTISTATE)
RECEPTOR MODEL
Developed on the basis of the kinetics of competitive and allosteric
inhibition.
It postulates that a receptor, regardless of the presence or absence of a
ligand, exists in two distinct states: the R(active) and R* (inactive) states.
R and R* are in equilibrium (equilibrium constant L), which defines the
basal activity of the receptor.
Occupied receptor can switch from its 'resting' (R) state to an activated
(R*) state, R* being favored by binding of an agonist but not an
antagonist.

30. AGONIST
A drug that binds to physiological receptor and mimic the regulatory
effects of endogenous substance.
It has high affinity and high intrinsic activity

31. PARTIAL AGONIST
• Full affinity + low intrinsic activity
• Partly as effective as agonist
• Cannot produce a full biological
response at any concentration
• ex: Pentazocine

32. INVERSE AGONIST
Full affinity & intrinsic activity <0 (0 to-1)
inverse agonists bind with the constitutively active receptors, stabilize
them, and thus reduce the activity (negative intrinsic activity).
Examples:-
Beta carbolines on BZD receptor
Chlorpheneramine on H1,
Risperidone/clozapine/chlorpromazine on 5-HT2a
Ziprasidone/olanzapine on 5-HT2c

33. ANTAGONIST
A drug is said to be an antagonist when it binds to a
receptor and prevents (blocks or inhibits) a natural
compound or a drug to have an effect on the
receptor. An antagonist has no activity.
Types of Antagonism
1. Chemical antagonism
2. Physiological /Functional antagonism
3. Pharmacokinetic antagonism
4 . Pharmacological antagonism
Competitive ( Reversible/irreversible)
Non competitive (Irreversible)

34. REFERENCES
• Goodman and Gilman's Pharmacological basis of therapeutics, 12thed
• Rang and Dale's pharmacology, 7th edition
• Alexander SPH, Mathie A, Peters JA (2011). Guide to Receptors and
• Channels (GRAC), 5th edn. Br J Pharmacol 164 (Suppli): $1-$324.
• Gurevich, E.V., et al., G protein-coupled receptor kinases: More than just
• kinases and not only for GPCRs, JPT Elsevier
doi:10.1016j.pharmthera.2011.08.001JPT-06382; GLIDA-GPCR ligand
database version 2.04 10/10/2010

35. THANKYOU