Cell -membraneIntroductionto Cell Membranes.pptx

1. Introduction to Cell Membranes
Definition and significance in cellular biology

2. Structure of the Cell Membrane
Phospholipid bilayer: amphipathic nature

Embedded proteins: integral vs. peripheral

Cholesterol’s role in fluidity

Carbohydrate chains: glycoproteins and glycolipids

1. Cell -membrane AMRITESH KUMAR BAC/52/11-12

2. INTODUCTION Skin of the cell. Termed by NAGELI & KRAMER. Also called plasma membrane or plasma lemma (PLOWE). Universal in occurrence. Cell membrane or biomembrane or unit membrane(ROBERTSON). Robertson give unit membrane concept.

3. Lipo portenaceous in composition. Tripartite/ Trilaminar & Assymetric in organization. Selectivly semipermeable in nature. GENERAL FEATURES

4. CHEMICAL COMPOSITION Protein- 40-76%. Lipid- 20- 53%. Carbohydrate-1-8%. Protein- mossaicness & selective permeable. Lipids-structural frame work of the membrane. Carbohydrate-restricted to outer surface.

5. DIFFERENT MODELS Lipid model- By overton. Lipid bilayer model-By Garter & Grandel. Lamellar model- By Danielle & Davson. Unit membrane model-By J.D . ROBERTSON. Fluid mosaic model-By SINGER & NICHOLSAN.

6. Fluid – mossaic model

7. Fluid – mossaic model ‘‘Protein iceberg in the sea of lipids.’’ Phospholipid bilayer forms structural frame work. The polar head of lipid molecule is directed outward & nonpolar tail is directed inward. Thus forms a water resistant barrier. Protein is of two types-extrinsic and intrinsic. Carbohydrates on outer surface either in the form of glycoprotein or glycolipid.

8. Modifications of cellmembrane Microvilli. Mesosomes. Lomasomes. Plasmodesmata. Desmosomes.

9. FUNCTIONS OF CELL-MEMBRANE Compartmentalisation. Protection. Differential permeability. Retentivity. Receptors for certain hormones. ETS-bacteria , thylakoid membrane of chloroplast,inner mitochondrial membrane. Endocytosis as well as exocytosis.