The Cell MembraneA layer found in all living

organisms

A Close look to your cell and plasma membrane (Fluid mosaic model)

Protein Carbohydrate Cholesterol phosphoLipid

1. Receptor2.Cell to cell adhesion3.Cell to cell recognition4.Transport protein

1. forms “H” bonds with water molecules surrounding the cell2. Receptor3.Cell to cell adhesion4.Cell to cell recognition

1.Prevents uncontrolled leakage2.Controls fluidity of membrane3.Gives mechanical stability, as without it cell bursts open

1.fatty acid tails act as barrier against polar molecules2.gives fluidity to membrane which allows it to stretch and reseal itself if disrupted as in Cytosis

Contents of the Cell

Membrane

Methods of substances transportation in and out of the Plasma membrane:

Simple diffusio

n

Facilitated

diffusionOsmosis

Active transport

Cytosis

PassiveActive requires (ATP)

+for substances that have weak charges and small molecular structure, so they can diffuse through the phospholipid bilayer.

EX: non-polar molecules.

+For diffusion of: large polar molecules as (glucose, amino acids) and ions as (Na, Ca, Cl). +Each substance is transported by a unique “channel protein”

These molecules can’t pass through phospholipid bilayer, due to hydrophobic interaction of fatty acid tails.

+Water molecules move down water potential

gradient by “Osmosis”.

+Forms of water potential inside the animal cell:-1- Hypertonic :- High

water pot. ( net movement of water out of

the cell ). 2- Hypotonic :- Low water pot. ( net movement of water into the cells, so

water potential increases inside the cells, water

moves out of the cell and cell bursts).

3- Isotonic :- equal tendency of water to

move in & out of the cells.

+For transportation of substances against concentration gradient.

+Each substance is transported by a unique “carrier protein”

EX:- Translocation of sucrose from mesophyll layer to phloem.-absorption of substances inside gut.-absorption of minerals by root hair cells.

1. “Endocytosis”: For engulfing of large molecules as (phagocytosis of white blood cells by phagocytes to form phagocytic vesicle, then 1ry lysosomes fuses with the vesicle forming 2ry lysosome which secretes enzymes to digest the engulfed material. End products of digestion are absorbed by cytoplasm, while undigested materials are expelled out of cell by 2.”Exocytosis”.3. “Pinocytosis” :- cell drinking4. “Micropinocytosis”