1. MOVEMENT OF SUBSTANCE
ACROSS THE PLASMA
MEMBRANE
Chapter 3
O2
CO2
CO2
O2

2. Movement of substance across plasma membrane
 Living cell carrying out life process:
a) Absorb water and nutrient
b) Excrete waste product
c) Exchange respiratory waste product
 These process IMPORTANT because :
a) Maintain optimal pH value
b) Obtain nutrient for metabolism
c) Eliminate toxic waste product
d) Secrete useful substance like hormone and enzyme
 Movement substance in and out via PLASMA MEMBRANE
~regulate exchange between content of cell and external envi.

3. STRUCTURE OF PLASMA MEMBRANE

4. 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

5.  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

6. 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

7. 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 membrane
 Selective permeability depend on~~Size and
polarity
a) Small & neutral (H2O, O2, CO2), Lipid soluble
~~easily across
b) big & polar (glucose, amino acid), charge ion
~~cannot cross and need help of TRANSPORT

8. MOVEMENT OF SUBSTANCE ACROSS
PLASMA MEMBRANE
Passive
transport
•Movement of substance
from concentration to
concentration
•Move DOWN their
concentration gradient
•NOT required energy
Simple
diffusion
Osmosis
Facilitated
diffusion
Active
transport
•Movement of substance
from concentration to
concentration
•Move AGAINTS their
concentration gradient
•Required energy

9.  In liquid and gases
 Molecule 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
PASSIVE TRANSPORT
1) Simple diffusion

10. PASSIVE TRANSPORT
2) osmosis
 Passive transport in WATER
 Diffusion 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

11. 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
Differences
SIMPLE
DIFFUSION
CRITERIA OSMOSIS
Gaseous and water Molecule Water
Not required semi
permeable
Membrane Required semi
permeable

12.  Some substance cannot cross plasma membrane
via simple diffusion
~ need help of transport protein
 Move DOWN concentration gradient
 Rate depend on number of transport protein
how fast it move
 The solute transported by carrier protein &
protein pore
 Protein pore small charge (ion) via pore in
protein
 Carrier protein uncharged polar~~ can change
shape and each carrier move specific substance
PASSIVE TRANSPORT
3) facilitated diffusion

13.  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

14. Active transport of sodium ions (Na+)

15. Comparison between passive transport and
active transport
Please make a mind mapping the movement of
substance across the plasma membrane