The cell membrane is composed of phospholipids, cholesterol, proteins, and carbohydrates. Phospholipids are amphipathic molecules with a hydrophilic head and two hydrophobic tails. They form a bilayer with different types concentrated on either side. Cholesterol modulates membrane fluidity and prevents small molecules from crossing. Membrane proteins carry out functions like transport and signaling, and can be integral or peripheral. Carbohydrates attached to proteins or lipids on the external surface form the glycocalyx and enable cell adhesion, recognition, and responses.

1. -Ladi Anudeep
ISM-IUK

5.  Components of cell membrane
1. phospholipids
2. cholesterol
3. proteins
4. carbohydrates

6.  Structure of phospholipid
 It is amphipathic
 Consists of
> two non polar hydrophobic tail made up
of two strings of hydrogen and carbon
> one charged polar hydrophilic head that
bears a phosphate group
>Phospholipids has two fatty acid chains and
a glycerol molecule and a phosphate group.

8.  Phospholipids in each half of the layer are
different
 For example, rbc consists of four types of
phospholipids.
 Phosphatidycholine and sphinogomycetin
seen more abundant in outer layer
 Phosphatidylserine and phosphodiethanol
amine concentrated towards inner layer of
plasma membrane

9.  Cholesterol
 A sterol lipid
 Very important component of cell membrane
 Made up four rings of hydrogen and carbon
 Modulates the fluidity and movement of cell
membrane components
 Strengthen the membrane by preventing some
small molecules from crossing it
 Found among hydrophobic tails in lipid layer
 When cholesterol molecules are more the fluidity
of membrane is less and vice versa

11.  Proteins
 Major components of cell membrane
 About 50% weight in cell membrane
 Functions as enzymes to speed up chemical
reactions
 Act as receptor for specific molecules
 Transports materials across cell membrane

12.  Two types of proteins
 1) INTERGRAL PROTEINS
> incorporated with in bi-layer
> can be extracted only by using
detergents to disrupt lipids
2) peripheral proteins
> exhibit a looser association with one if the
two membrane surfaces
> can be easily extracted from cell
membrane by using salt solutions

13.  Polypeptide chains of many integral proteins
span the membrane several times from one
side to other are called Multipass trans-
membrane proteins.
Types of transmembrane proteins
>Receptors
>Channels

15.  Carbohydrates
 Found attatched to proteins or lipids
 Found on outside of cell membrane
 When attatched to proteins called as
glycoproteins
 When attached to lipids are called as
glycolipids

16.  Carbohydrates moeties of glycoproteins and
glycolipids project from external surface of
plasma membrane contribute to form
glycocalyx
 Functions of glycocalyx
> cell adhering
>cell recognition
> response to hormones