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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