1. Cell Membrane Structure
Dr. V.P.C. Rajakaruna
MBBS(COLOMBO)

2. Content
Introduction to cell membrane
Composition

3. What is cell membrane? Outer most covering of the cell
Cell membrane separates living cell from nonliving surroundings
Selectively permeable
Consists of phospholipids and proteins mainly and other macromolecules such as cholesterol and carbohydrate

4. Fluid-mosaic model
Phospholipid bilayer with embedded proteins, fluid consistency and a mosaic pattern of embedded proteins

6. Composition

7. Phospholipids Fatty acid tails hydrophobic Phosphate group head
hydrophilic
Arranged as a bilayer
Phosphate
Fatty acid

8. Hydrophilic (water-loving) polar heads of the molecules lie on the outward-facing and inward-facing surfaces of the membrane.
Hydrophobic (water-fearing) nonpolar tails extend to the interior of the membrane.

9. Phospholipid bilayer polar hydrophilic heads nonpolar hydrophobic
tails
polar
hydrophilic
heads

10. Other components

11. Proteins Peripheral proteins Integral proteins
loosely bound to surface of membrane
cell surface identity marker
Integral proteins
penetrate lipid bilayer, usually across whole membrane
transmembrane protein
transport proteins
channels, permeases (pumps)

12. Many Functions of Membrane Proteins
Outside
Plasma
membrane
Inside
Enzyme activity
Cell surface receptor
Transporter
Cell surface identity marker
Attachment to the cytoskeleton
Cell adhesion

13. Carbohydrates
Glycolipids - phospholipids with carbohydrate chains attached
Glycoproteins -proteins have carbohydrate chains attached.
The carbohydrate chains of glycolipids and glycoproteins form the glycocalyx

14. Functions of the Glycocalyx
cell-to-cell recognition
cell-cell adhesion
reception of signal molecules.
The diversity of carbohydrate chains is enormous, providing each individual with a unique cellular “fingerprint”.

15. Cholesterol
Helps maintain the integrity of the cell membrane, and plays a role in facilitating cell signaling ( meaning the ability of your cells to communicate with each other), protecting the proteins and giving them a supportive cover.