UNDERSTANDING THE MOVEMENT OF

SUBSTANCES ACROSS THE PLASMA MEMBRANE IN

EVERYDAY LIFE

ACROSS PLASMA MEMBRANEMovement

Membrane Structure

Necessity for the Moveme

nt

Function of

Plasma

Membran

e

Permeability

of the Phospholipid Bilay

er

Types of Transport

Passive Transpo

rt

Active Transpo

rt

Solution of Concentration

Hypotonic

Hypertonic

Isotonic

Membrane StructureSemi-permeable lipid

bilayer

Control water and

other substances in and out

Functions:•Protect the cell•Separate the intracellular component from extracellular environment•Controls what enter and exits the cell

Necessities for the Movement of Substances across the

Plasma Membrane

To transport nutrients into the cell

excrete metabolic waste

 maintain the pH value and ionic concentration of the cell

 gases exchange

FUNCTION OF PLASMA MEMBRANE

the transportation of materials

the transportation of materials

act as an attachment to the non-living matter that is found outside the cell membrane

act as an attachment to the non-living matter that is found outside the cell membrane

maintains a suitable 'cell potential'.

maintains a suitable 'cell potential'.

Permeability of the Phospholipids Bilayer

Is determine by:

SIZE POLARITYCHARGE

Substance can move through

• Non polar molecule: fatty acid, vitamins (A, D, E, K), steroid

• Oxygen, Carbon dioxide, Water

Substance cannot move through

• Polar molecule: Polysaccharide, Amino acids, glucose, nucleic acid

• Ions: Sodium ion, Potassium ion, Calcium ion, Hydrogen ion.

PASSIVE TRANSPORT

Sim

ple diffusion

•The simplest type

•No energy need

•Small molecules can pass through :Oxygen,carbon dioxide,lipid soluble molecules.

•net movement of molecules or ions from higher to lower concentration until equilibruim achieved.

Os

mosis

•involves only water molecules•net movement of freely moving water molecules from a low to high solute concentration.•important to cell because cell need adequate water to function well.

Facilitated diffusion

•No energy need•Water soluble which are not soluble in lipids cannot pass through the phospholipids bilayer but with the aids of carrier protein and pores

ACTIVE TRANSPORT

molecule transported from an area of low concentration to an area of high concentration, work must be done to overcome the influences of diffusion and osmosis. 

molecule transported from an area of low concentration to an area of high concentration, work must be done to overcome the influences of diffusion and osmosis. 

 

Since in the normal state of a cell, large concentration differences in K+, Na+ and Ca2+ are maintained, it is evident that active transport mechanisms are at work.

 

Since in the normal state of a cell, large concentration differences in K+, Na+ and Ca2+ are maintained, it is evident that active transport mechanisms are at work.

they are pumping something (usually ions) from areas of lower to higher concentration.they are pumping something (usually ions) from areas of lower to higher concentration.

SOLUTION OF CONCENTRATION

Solutionconcentration

HYPERtonicHYPOtonic

ISOtonic

On Plant CellHypotonic•external solution is hypotonic to the cell sap•movement of water diffusing into the cell by diffusion•vacuole filled with water and expands•cell wall expand slighlt and become turgid

Hypertonic•external solution is hypertonic to cell sap•net movement of water out of the cell by osmosis•vacuole become smaller. Plasma membrane pull away from the cell walls•cell become flaccids

Isotonic•external solution is isotonic to cell sap•no net water movement into and out of the plant cell•no change in size or shape of the cell

On Animal CellHypotonic• cause water to move into the cell and cause it to expand.• Water concentration inside the cell is lower than outside the cell• water molecules is transported into the red blood cells by osmosis•  The red blood cells will inflate and finally burst because the thin membrane cannot

withstand the high pressure inside the cell.• undergo haemolysis

Hypertonic• Water concentration inside the cell  is lower than outside the cell• shape of the cell becomes distorted and wrinkled as water leaves the cell• a solution having a lesser solute concentration than the cytosol• If water molecules continue to diffuse into the cell, it will cause the cell to swell, up

to the point that cytolysis (rupture) may occur

Isotonic• cell in an isotonic environment is in a state of equilibrium with its surroundings• osmotic pressure becomes equal; the force of water trying to exit and enter the cell

balances out.• No change will occur in the cell.