The document presents a comprehensive overview of the cell membrane, including its definition, history, structure, and functions. It discusses the chemical composition, including lipids and proteins, and outlines the processes of passive and active transport across the cell membrane. Key concepts such as diffusion, osmosis, and facilitated diffusion are explained, along with the significance of the lipid bilayer and membrane proteins in cellular function.

1. TOPIC: CELL MEMBRANE
SCHOOL OF CLINICAL SCIENCES – MAKENI
GROUP 5
Lecturer: DR. MASERAY
MODULE: BIOCHEMISTRY PRESENTATION

2. 1. PETER S. SAMURA LEADER
2. ZAINAB KADIATU KAMARA
3. JOHN ET KALLON
4. NOAH JALLOH
5. SENNATU KOROMA
6. OSMAN CONTEH
GROUP MEMBERS

3.  DEFINATION OFCELL MENBRANE
 HISTORY OF CELL MEMBRANE
 STRUCTURE OF CELL MEMBRANE
 FUNCTION OF CELL MEMBRANE
 CHEMICAL COMPOSITION
 REACTION OF CELL MEMBRANE
OUTLINE

4. CELL MEMBRANE

5. Plasma/ cell membrane
The Plasma membrane or cell membrane is a thin,
biological membrane present in all eukaryotic and
prokaryotic cells that forms a boundary between the
cell and it’s environment and regulating the flow of
materials into and out of the cell.
Intro:……….

6. The first incite into chemical nature of the membrane was
obtained by Ernst Overtom in 1890s.
He knew that the non- polar solutes dissolved very easily in
the non-polar solvents then polar solvents and the polar
solvents has opposite solubility.
So he realised that the substances entering the cell has to be
dissolved in the outer boundary of cells is due to lipids.
Irvin Langmuir in 1970s doing his research in nature of oil
film, found that the membrane was made of mono layers of
lipids and they are arranged vertical with hydrocarbon chains
away from water and carboxyl groups in contact with the
surface of water.
This finding was a key in understanding the lipid bilayers and
cell membrane structure.
History

7.  the two Dutch scientists E’Gorter and F’Grendel in the 1925
were the first to find that the membrane was made of two
layers of lipids (lipid bilayer) with hydrophilic heads and
hydrophobic tails , but they could not explained about the
solute permeability or the surface tension.
In 1935 Hugh Davson and James Danielle proposed that the
membrane is made of lipids bilayers and on both outer
and inner surface there was a lining of globular proteins.
Cont:…………

8.  THE structure is made up of two micro molecules either lipids
and protein .
 The structure of the cell membrane is not fixed neither regal but
dynamic
 Cell membrane structure gives the cell a unique structure and
shape
 The cell membrane structure help to organize the cell in an
organized manners
 The cell membrane structure allows specifics substances to
enter from the environment selective permeable membrane
STRUCTURE OF CELL MEMBRANE

10. The basic function of the cell membrane is to protect the
cell from its surroundings
Its consists of the phospholipids bilayers with embedded
proteins
Regulate transport in and out of the cell ( selectively
permeable)
Water can freely pass the membrane
Contains the cytoplasm(fluid in the cell)
Provide a binding sites for enzymes
Allow cell recognition
Ions and large molecules cannot cross without assistance
Interlocking surface binds cells together (junction)
Provide anchoring site for filaments of cytoskeleton
Function of cell membrane(plasma)

11. Cell membranes
contain a variety of
biological molecules,
mainly lipids and
proteins.
Carbohydrates are
present in a very small
amount,
predominantly as
glycoproteins.
.
Chemical composition of plasma
membrane
plasma membrane
lipids
40-45 %
carbohydrate
1-5%
proteins
50 - 55%

12. PHOSPHOLIPIDS > 55%
CHOLESTEROL =40-45%
GLYCOLIPID=2%
1. MEMBRANE LIPIDS

13. They are lipids that form bilayers of plasma
membrane.
It contains hydro phobic tail which face towards each
other and hydrophilic head facing the cytoplasm and
extracellular fluid.
The hydrocarbon chains forms hydrophobic tail while
the phosphate group and amino acids form
hydrophilic heads.
The lipid bilayer is semi permeable, allowing only
certain substances to diffuse through.
PHOSPHOLIPIDS

15. CHOLESTEROL

17. They are lipids
with a
carbohydrate
attached to it
It provides
energy and acts
as markers for
cellular
recognition.
GLYCOLIPIDS

19. Integral membrane proteins
Peripheral membrane proteins
Glycoproteins
2. MEMBRANE PROTEINS

20. These are proteins which are
embedded within the lipid bilayer
and it acts as channels through
which substances diffuse between
the extracellular and intracellular
fluid.
INTEGRAL MEMBRANE PROTEINS

21. It is attached to the inner surface
of the membrane and do not
penetrate the lipids bilayer.
They function as enzymes and
receptors.
PERIPHERAL PROTEINS

22. They are embedded in the cell
membrane.
Its is formed by attachment of
carbohydrate molecules to the protein.
It helps in cell – cell communication and
molecule transport across the
membrane.
GLYCOPROTEIN

23. Chemical reaction
Passive transport
In order to understand how substances move passively across a cell
membrane, it is necessary to understand concentration gradient and
diffusion.
A concentration gradient is the different in concentration of a substance
across a space.
Molecules(ion) will spread or diffuse from where they are more
concentrated to where they are less concentrated until they are equally
distributed in that space. (when molecules move in this way, they are said
to move down their concentration gradient.)
Three common type of passive transport includes
1. Simple diffusion
2. Osmoses diffusion
3. Facilitated diffusion
REACTION OF CELL MEMBRANE

24. It is the net movement of solvents from a area of high
concentration to a area of less concentration until the
concentration of solute reaches the state of equilibrium.
Due to lipids nature of the plasma membrane holding non-
polar molecules like oxygen, carbon dioxide and nitrogen
pass rapidly across the membrane according to their
concentration gradient.
It occurs because the molecules has free energy and they
are always in motion .
Simple diffusion

25.  When aver a substance exists in greater concentration on
one side of a semi permeable membrane, such as the
plasma membrane, any substance that move down it
concentration gradient across the membrane will do so .
Consider substance that can easily diffuse through the
lipids bilayer of the cell membrane, such as the gases,
oxygen (o2) and CO2.
 O2 generally diffuse into the cell membrane it is more
concentrated outside of them and CO2 typically diffused
out of the cells because it more concentrated inside of
them.
 Neither of these examples requires any energy on the part
of cell membrane and therefor they use passive transport
to move across the membrane.
Cont…….

26.  Osmosis is the diffusion of water through a semi
permeable membrane water can move freely across
the cell membrane of all cells either through protein
channels or by slipping between the lipids tails of the
membranes itself .
 However, it is concentration of solute within the
water that determine weather or not water will be
moving into the cell, out of the cell, or both.
Osmosis

27.  Facilitated diffusion is the diffusion process used for those
substances that cannot cross the lipid bilayer due to their
side and or polarity a common examples of facilitated
diffusion is the movement of glucose into the cell, where it
is use to make ATP. Although glucose can be more
concentrated outside of the cell, it cannot cross the lipids
bilayers via simple diffusion because it is both large and
polar. to resolve this, a specialized carrier protein call the
glucose transporter will transfer glucose molecule into the
cell to facilitate it inward diffusion.
 There are many other solute that most undergo facilitated
diffusion into the cell, such as amino acid or to move out of
the cell such as wastes.
 Because facilitated diffusion is a passive process, it does
not required energy expenditure by the cell .
Facilitated diffusion

28.  it is the transport of molecules across the cell membrane
from an area of low concentration to and area of high
concentration using cellular energy .
Active transport occurs with the help of carrier proteins.
 There are two actives site in this carrier proteins.
One it receptors site which is recognizes the substances to
be carried and the other it that which releases the energy
in form of ATP. Example transportation of sodium out of
cell and potassium into the cell.
Active transport

29. There are two form of active
transport
1. Primary active transport
2. Secondary active transport
Form of active transport

30. When the process used chemical energy in the form of
ATP, redox energy or photon energy to transport
substances across the membrane, it is call primary active
transport
The energy is derived directly from the breakdown of the
ATP or some other high energy phosphate compounds.
The protein act as point to transport ions most of the
enzymes that perform this transport are transfers
membrane ATP-ase then the primary ATP- ase which is
universal to all animal cell is sodium-potassium pump
which maintains the cell potential.
Primary active transport

31. When the process use electrochemical gradient to
transport substances it is called secondary active transport
 here the energy is derived secondarily from the energy
that has been stored in the form of ionic concentration
difference between the two site of the membrane, created
in the first place by primary active transport.
The pore forming proteins acts as channels across the cell
membrane for transporting substances the energy stored
in Na+ , H+ concentration gradient is used to transport
other solutes or ions.
Secondary active transport

32.  By Harshraj s shinde
 K.k. Wagh colledge of Agrculture Biotechnology
 Dr.Areeba Ghayas
Refrences

33. Thanks!!!
Any questions