CELL MEMBRANESTRUCTURE AND FUNCTIONS

By. Dr Nazish

Learning ObjectivesLearning Objectives

1.1. The bilayer structure of plasma membrane The bilayer structure of plasma membrane 2.2. Types of lipids in the membrane: physiological Types of lipids in the membrane: physiological

significance significance 3.3. Physiological importance of proteins in the Physiological importance of proteins in the

plasma membrane plasma membrane 4.4. Types of carbohydrates: physiological Types of carbohydrates: physiological

importance importance 5.5. Selective permeability characteristics of the Selective permeability characteristics of the

plasma membrane. plasma membrane.

Lipid bilayer

Intracellularfluid

Extracellularfluid

Choline

Phosphate

Glycerol

Fatty acid

Head(polar, hydrophilic)

Tails(nonpolar, hydrophobic)

-

= Negative charge on phosphate group-

Lipid bilayer is

phospholipids

Lipid bilayer

ICF (water)

ECF (water)Polar heads(hydrophilic)

Nonpolar tails(hydrophobic)

Polar heads(hydrophilic)

Phospholipids form a bilayer That has a hydrophobic interior.

This interior is sandwiched between hydrophilic inner and outer surfaces.

Functions of the lipid bilayer

Cholesterol : allows the membrane to be fluid.

- Forms the basic structure of the membrane.- Hydrophobic interior is a barrier to water- soluble substances- allows diffusion of fat soluble substances

Extracellular fluid

Lipid bilayer

Intracellularfluid

Dark lineLight space

Appearance using an electron microscope

Dark line

Glycoprotein GlycolipidCarbohydratechain

Channel

Variousmembraneproteins

Cholesterolmolecule

Phospholipid molecule

Functions of plasma membrane

Channel proteins

Functions of membrane proteins

Carrier proteins

Functions of plasma membrane

Receptor proteins

Functions of plasma membrane

Docking marker acceptors

Functions of plasma membrane

cell adhesion molecules

Functions of cell membrane

Self identification markers

Membrane-Membrane-bound bound enzymesenzymes

ReceptorReceptorCarrierCarrier moleculesmolecules

Functions of membrane proteins

ChannelsChannels

Docking-Docking-marker marker

acceptorsacceptors

Cell adhesion Cell adhesion moleculesmolecules Cell identity Cell identity

markersmarkers

Channels: span the membrane as water-filled poresChannels: span the membrane as water-filled poresCarrier moleculesCarrier moleculesReceptor sites: proteins that bind with specific moleculesReceptor sites: proteins that bind with specific moleculesDocking-marker acceptors (on inner surface for Docking-marker acceptors (on inner surface for secretory vesicles)secretory vesicles)Filamentous meshwork (cytoskeleton)Filamentous meshwork (cytoskeleton)Membrane-bound enzymesMembrane-bound enzymesCell adhesion molecules : protrude from surfaceCell adhesion molecules : protrude from surfaceCell identity markers in conjunction with carbohydrates Cell identity markers in conjunction with carbohydrates

Functions of membrane proteins.

CHO containing Surface markers involved in tissue CHO containing Surface markers involved in tissue growth.growth.Cell identity markers in conjunction with proteins Cell identity markers in conjunction with proteins

Functions of membrane carbohydrates.

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