Discipline: Physiology Topic: Cell Membrane I hope this video gonna help you in your in FMGE as well as in various PG entrance exam. Here, I discuss only those topic that are very important regarding your coming exam. Stay tuned with me. For better understanding wacth this https://youtu.be/lNiTDLDxyZg Thanks for your kind attention. Regards, Dr.Nishu Verma

2. Cell Membrane
Prokaryotic and eukaryotic cells are enclosed by Semi permeable membrane that :
Prokaryotic and eukaryotic cells are enclosed by Semi permeable membrane that :
Prokaryotic and eukaryotic cells are enclosed by Semi permeable membrane that :
Prokaryotic and eukaryotic cells are enclosed by Semi permeable membrane that :
separates the interior of the cell
the cell
the cell
the cell from the outside environment
regulates the transport of materials “in” and “out” the cell
the cell
the cell
the cell
Also serves as attachment site for other molecules, serves in cell signaling and
cell communication.
Thickness of Cell membrane is about :
The cell membrane
The cell membrane
The cell membrane
The cell membrane is composed almost entirely of proteins and lipids.
The approximate composition is proteins 55% , phospholipids 25% , cholesterol
proteins 55% , phospholipids 25% , cholesterol
proteins 55% , phospholipids 25% , cholesterol
proteins 55% , phospholipids 25% , cholesterol
13%, other lipids 4%, and carbohydrates 3%.
13%, other lipids 4%, and carbohydrates 3%.
13%, other lipids 4%, and carbohydrates 3%.
13%, other lipids 4%, and carbohydrates 3%.

3. Membranes are asymmetric structures
asymmetric structures
asymmetric structures
asymmetric structures because
o Proteins have unique orientations in membranes
o External location of the carbohydrates attached to membrane proteins

4. 1.Lipid (~ 40%)
• Phospholipids (25%):
Phospholipids (25%):
Phospholipids (25%):
Phospholipids (25%):
1. The polar head (hydrophilic) made from glycerol
and phosphate
2. The non-polar part which has two fatty acid tails
(hydrophobic).
Phospholipids spontaneously arrange in a bilayer
• Phospholipids are held together in a bilayer by
hydrophobic interactions
hydrophobic interactions
hydrophobic interactions
hydrophobic interactions (weak associations)
• Phospholipids can move horizontally or
occasionally laterally to increase fluidity.
• Phospholipids with short or unsaturated fatty
acids are more fluid.

5. Cholesterol (13%):
Cholesterol (13%):
Cholesterol (13%):
Cholesterol (13%):
• Cholesterol found in both leaflets.
o The cholesterol
cholesterol
cholesterol
cholesterol serves to stabilize the membrane at normal body
temperature (37°C).
o Cholesterol is important for the maintenance of the correct
permeability and fluidity membrane.

6. • Other lipids (4%).
• Lipid-soluble substances
Lipid-soluble substances
Lipid-soluble substances
Lipid-soluble substances
• cross cell membranes because they can dissolve in the hydrophobic lipid
bilayer
• e.g. O2 , CO2 , steroid hormones
• Water
Water
Water
Water-
-
-
-soluble substances
soluble substances
soluble substances
soluble substances
• cross through water-filled channels, or pores, or may be transported by
carriers.
• e.g. Na+ , Cl– , glucose, H2O

7. 2.Proteins (~ 55%)
1. Integral proteins:
imbedded in, the cell membrane through hydrophobic interactions and
hydrophobic interactions and
hydrophobic interactions and
hydrophobic interactions and some by
Van der Waals Forces
Van der Waals Forces
Van der Waals Forces
Van der Waals Forces
Function in transport.
Include:
:
:
:
2. Peripheral proteins
loosely attached to:
cell membrane
cell membrane
cell membrane
cell membrane
integral protein
integral protein
integral protein
integral protein
Functions in adhesion and cell recognision.

8. 3.Carbohydrates (3%)
Glycoprotein and glycolipids .
Funtions:
participate in cell recognition and adhesion,
Cell to cell signaling
cell-pathogen interactions during infection
Blood groups are determined by carbohydrates that present on
the cell surface of erythrocytes, and they also have the ability
to trigger immunological responses.

9. Membrane fluidity and the fluid
mosaic model of membrane:
• The fluid mosaic model of membrane structure proposed in
1972 by Singer and Nicolson.
• According to this model:
Integral membrane proteins are like “icebergs” floating in a sea of
phospholipid molecules.
o The fluidity of the membrane is determined by:
• The temperature at which membrane structure undergoes the
transition from ordered to disordered (i.e. melts) is called the
“transition temperature” (Tm).
Increase Tm means more rigid (decrease fluidity) membrane.

10. As
As
As
As temperature
temperature
temperature
temperature increases
increases
increases
increases, the membrane fluidity raises.
The presence of unsaturated fatty acyl chains in phospholipids and
glycolipids also increases membrane fluidity and Decrease Tm.
Longer and more saturated fatty acid decreases membrane fluidity
and increase Tm.
• Cholesterol acts as a buffer to modify the fluidity of membranes.
o At temperatures below the Tm:.
o At temperatures above the Tm:

11. Quick Digest:
Mass Ratio of protein
Mass Ratio of protein
Mass Ratio of protein
Mass Ratio of protein to lipid of biological
membrane is
The ratio is maximum in inner mitochondrial membrane
(3.2) > Sarcoplasmic reticulum (2.0) > Outer
mitochondrial membrane (1.1)
The ratio is minimum in myelin (0.23)
In human erythrocyte the ratio is

12. PREVIOUS YEAR
QUESTIONS
(AIIMS, JIPMER,PGI etc)

13. 1. True about lipid bilayer of cell Membrane: [PGI]
a. Asymmetrical arrangement of cell membrane component
b. Lateral diffusion of ions
c. Symmetrical arrangement of cell membrane components
d. Not made up of amphipathic lipids

14. 2. Membrane fluidity is increased by: [AIIMS]
a. Stearic acid
b. Palmitic acid
c. Cholesterol
d. Linoleic acid

15. 3. Transition temperature of lipid bilayers of cell membrane
is increased by: [AIIMS]
a. Cholesterol
b. Saturated fatty acids
c. Hydrocarbons
d. Unsaturated fatty acids

16. 4. Which of the following membrane has the highest
protein content per gram tissue? [AIIMS]
a. Inner mitochondrial membrane
b. Outer mitochondrial membrane
c. Plasma membrane
d. Myelin sheath

17. 5. Lipids and proteins interact in membrane by: [PGI ]
a. Hydrophobic interactions
b. Both hydrophobic and covalent interactions
c. Covalent bonds
d. Hydrogen bonds

18. 6. The transmembrane region of protein is likely to
have: [JIPMER]
a. A stretch of hydrophilic amino acids
b. A stretch of hydrophobic amino acids
c. A disulphide loop
d. Alternating hydrophilic and hydrophobic amino acids

19. Thanks
for
your Attention!!!