MOVEMENT OF SUBSTANCE ACROSS THE

PLASMA MEMBRANE

Chapter 3O2

CO2

CO2

O2

Movement of substance across plasma membrane

Living cell carrying out life process:a) Absorb water and nutrientb) Excrete waste productc) Exchange respiratory waste product

These process IMPORTANT because :a) Maintain optimal pH value b) Obtain nutrient for metabolismc) Eliminate toxic waste productd) Secrete useful substance like hormone and enzyme

Movement substance in and out via PLASMA MEMBRANE ~regulate exchange between content of cell and external envi.

STRUCTURE OF PLASMA MEMBRANE

PLASMA MEMBRANE…

Was proposed by S.J Singer and G. Nicolson (1972) ~FLUID MOSAIC MODEL

Based on this model, structure of plasma membrane compose of phospholipids bilayer and various type of protein molecule

A phospholipids is AMPHIPATHIC MOLECULE~ has both hydrophilic region and hydrophobic region

Polar head is HYDROPHILIC (attracted to water) while non-polar tail is HYDROPHOBIC (repelled by water)

The interaction ~~prevent adjacent phospholipids from packing too tightly ~more fluid

Cholesterol ~stabilize and strength the plasma membrane, more flexible

Protein Pore protein~form channel Carrier protein~act as a carrier

PLASMA MEMBRANE

According to this model: Phospholipids, protein and other component of

membrane are not rigid or static, but form a dynamic and fluid structure

Protein molecule embedded in phospholipis bilayer float freely

Protein and phospholipids free to move sideways within membrane~~FLUID CHARACTERISTIC

Various protein built into plasma membrane~form MOSAIC PATTERN

THE PERMEABILITY OF PLASMA MEMBRANE

Plasma membrane ~PARTIALLY PERMEABLE @ SEMI-PERMEABLE~ certain substance can move freely while other cannot

Membrane envelope organelles and allow certain substance enter or leave the organelles

Eg: Visking tube, cellophane tape, egg membraneSelective permeability depend on~~Size and polarity

a) Small & neutral (H2O, O2, CO2), Lipid soluble ~~easily acrossb) big & polar (glucose, amino acid), charge ion ~~cannot cross and need help of TRANSPORT PROTEIN Pore protein ~small, water soluble & ion Carrier protein ~have site that can combine to specific molecule

MOVEMENT OF SUBSTANCE ACROSS PLASMA MEMBRANE

Passive transport

•Movement of substance from concentration to

concentration• Move DOWN their

concentration gradient• NOT required energy

Simple

diffusionOsmosi

s Facilitate

d diffusion

Active transport• Movement of

substance from concentration to

concentration• Move AGAINTS their concentration gradient• Required energy

In liquid and gasesMolecule diffuse DOWN concentrated

gradient via plasma membrane until EQUILIBRIUM is reach

At eq. molecule continue move back and forth, but no net change to both side

Soluble are small uncharged & molecule dissolve in fats

(vit A, D, E, and K)The bigger concentration gradient, the

faster rate of diffusionEg: gaseous exchange in lung

PASSIVE TRANSPORT1) Simple diffusion

PASSIVE TRANSPORT2) osmosis

Passive transport in WATERDiffusion of water (solvent) DOWN concentration gradient via semi permeable membrane

Water move from higher [water] ~dilute~ to a region of lower [water] ~concentrated~ until concentration of both side are same. Then water molecule move at a same rate in both direction

Eg : absorption of water by root hair of a plant

Comparison between simple diffusion and osmosis

Similarities• Not require energy. Kinetic energy molecule/ion that

make them move randomly• Move DOWN concentration gradient

•Move high concentration region to low concentration gradient until reach equilibrium

DifferencesSIMPLE

DIFFUSIONCRITERIA OSMOSIS

Gaseous and water

Molecule Water

Not required semi permeable

membrane

Membrane Required semi permeable membrane

Some substance cannot cross plasma membrane via simple diffusion

~ need help of transport proteinMove DOWN concentration gradientRate depend on number of transport protein how fast it move The solute transported by carrier protein & protein

poreProtein pore small charge (ion) via pore in proteinCarrier protein uncharged polar~~ can change

shape and each carrier move specific substanceEg: transportation of glucose, amino acid and mineral

ions across villus in ileum

PASSIVE TRANSPORT3) facilitated diffusion

Movement of substance across plasma membrane from a region of LOW concentration to region of HIGH concentration (AGAINTS concentration gradient)

Require work to transport against concentration so need energy ~ATP

Perform by specific protein molecule ~~need energy to change the shape ~~to pump or transport

EG : intake of mineral ions by root hair of plant

ACTIVE TRANSPORT

Active transport of sodium ions (Na+)

Comparison between passive transport and active transport

Please make a mind mapping the movement of substance across the plasma membrane