cell membrane and cell transport

Presented by: Nisha Lakra1st sem Applied GeneticsBrindavan College

Presented to : Mr. Aditya Sathyan Cellular Physiology Brindavan College

Introduction

• Boundary that separates the living cell from it’s non-living surrounding.

•The cell membrane is selectively permeable.

•It consists of the phospholipid bilayer with embedded proteins.

•Most widely accepted model is Fluid-Mosaic Model

Oligosaccharides

CytoplasmCytoplasm

Membrane Proteins

Cholesterol

OuterSurface

Fluid Mosaic Modelof Membrane Structure

PhospholipidBilayer

Macromolecules found in Membranes

• Lipids– Phospholipid bilayer– Cholesterol

• Proteins– Transport proteins– Receptor proteins– Recognition proteins

• Carbohydrates– Oligosaccharides on glycoproteins

The plasma membrane “fluid” is a double layer of phospholipids.

The plasma membrane “mosaic” is a collection of proteins.

Transport Processes• Movement of substances across the cell

membrane

• Passive transport– No energy input required– Simple Diffusion, Facilitated Diffusion, Osmosis

• Active transport– Substances move from [low][high]– Protein carriers, Endocytosis, Exocytosis

Simple Diffusion(extracellular fluid)

(cytoplasm)

Some molecules

diffuse freelyacross

Some moleculesdiffuse freely

across

(lipid soluble molecules, CO2, O2, H2O )

Now known to require transport proteins called aquaporins

Facilitated Diffusion: Use of Carriers to Assist with Diffusion

Carrier proteinhas binding sitefor molecule

Molecule entersbinding site

Carrier protein changesshape, transportingmolecule across membrane

Carrier protein resumesoriginal shape

(Inside Cell)(Inside Cell)

(OutsideCell)

(OutsideCell)

DiffusionChannelProtein

DiffusionChannelProtein

Diffusion

Gradient

Molecule inTransit

Molecule inTransit

Osmosis• Diffusion of water across a differentially permeable

membrane• Water moves from [high] [low]

Normal RBCs

Isotonic Solution

The Effects of Osmosis

Equal movement of waterinto and out of cells

Net movement ofwater out of cells

Net movement ofwater into cells

Shriveled RBCs

Swollen RBCs

Hypertonic Solution Hypotonic Solution

Active Transport with Protein Carrier

Inside CellInside Cell

Outside CellOutside Cell

EnergyProviderEnergy

ProviderSpent Energy

ProviderSpent Energy

Provider

TransportedMolecule

TransportedMolecule

1 2 3 4

Endocytosis

(extracellular fluid)

Pinocytosis

vesicle containingextracellularfluid)(cytoplasm)

12 3

cell

(extracellular fluid)

(cytoplasm)

1

23 4

coatedpit forming

Receptor-mediatedEndocytosis

Phagocytosis

coatedvesicle

nutrientsreceptors

food particle

pseudopodparticle enclosedin food vacuole

Exocytosis

(cytoplasm)

1

Vesicle

(extracellular fluid)

plasma membrane

2

SecretedMaterial

3

THANK YOU