What is Hypertonic Solution?

Hypertonic solution is the solution that has lower water potential than the other solution.

Water Concentration and Solute Concentration of a Cell in a Hypertonic Solution

1. Water concentration: Water concentration inside the cell is higher than outside the cell.
2. Solute Concentration: Solute concentration inside the cell is lower than outside the cell.

Effect of Hypertonic Solution on Animal Cell

1. If an animal cell such as red blood cell is placed into a hypertonic solution, water molecules is transported out from the red blood cells by osmosis (as shown in the diagram above).
2. The red blood cells will shrink due to the lost of water from the cell and probably die.
3. The red blood cells are said to undergo crenation .

Effect of Hypertonic Solution on Plant Cell

1. When a plant cell is placed in a hypertonic solution, water molecules is transported out from the cell by osmosis.
2. The vacuole and cytoplasm are then shrink due to lost of water.
3. The plasma membrane is pulled away from the cell wall..
4. The process is called plasmolysed.

Summary:

What is Isotonic Solution?

In isotonic solutions, both solutions have equal water potential.

Water Concentration and Solute Concentration of a Cell in a Isotonic Solution

Water concentration and solute concentration are equal in both solutions.

Effect of Isotonic Solution on Animal Cell

1. If an animal cell such as red blood cell is placed into a isotonic solution, amount of water molecules is transported into the red blood cells by osmosis is equal to the amount of water molecules transported out from the cell (as shown in the diagram above).
2. Therefore the amount of water in the cell remain unchanged.
3. The red blood cells maintain their shape.

Effect of Isotonic Solution on Plant Cell

1. When a plant cell is placed in an isotonic solution, solute concentration in the external solution is equal to the solute concentration i the cell sap.
2. Therefore the rate of diffusion of water into the cell is equal to the rate of diffusion of water out from the cell.
3. As a result, the shape of the cell remain unchanged.

What is Hypotonic Solution?

Hypotonic solution is the solution that has higher water potential than the other solution.

Water Concentration and Solute Concentration of a Cell in a Hypotonic Solution

1. Water concentration: Water concentration inside the cell is lower than outside the cell.
2. Solute Concentration: Solute concentration inside the cell is higher than outside the cell.

Effect of Hypotonic Solution on Animal Cell

1. If an animal cell such as red blood cell is placed into a hypotonic solution, water molecules is transported into the red blood cells by osmosis (as shown in the diagram above).
2. The red blood cells will inflate and finally burst because the thin membrane cannot withstand the high pressure inside the cell.
3. The red blood cells are said to undergo haemolysis.

Effect of Hypotonic Solution on Plant Cell

1. When a plant cell is placed in a hypotonic solution, water molecules is transported into the cell by osmosis.
2. The water is then stored in vacuole causing it to expand and exerts pressure on the cell wall. This pressure is called turgor pressure.
3. The turgor pressure caused the plant cell to become firm or turgid.
4. The rigid cell wall prevents cell from bursting.

What is Active Transport?

1. Active transport is the movement of substances across the plasma membrane of cells against the concentration gradient (From lower concentration to higher concentration).
2. Since it is against the concentration gradient, energy is needed in the process.
3. Video below shows how particles are transported through the carrier protein in active transport. Take notes that the process only happens when the carrier protein receives energy from an ATP.

Basic Requirements in Active Transport

1. Presence of the carrier protein
2. Presence of ATP (Adenosine Triphosphate)

Function of the ATP

ATP is the source of energy in active transport. It supplies energy to the carrier protein to carry out the process. It is converted into ADP (Adenosine Diphosphate) after the reaction.

Mechanism of Active Transport

The video below shows how sodium ions and potassium ions are transported through the plasma membrane by a carrier protein.

Examples of Active Transport

Intake of mineral ions by the root hairs of a plant.

What is Facilitated Diffusion?

Facilitated diffusion is the passive transport of substances across the plasma membrane with the help of transport proteins such as the channel protein and the carrier protein.

Substances Pass through the Plasma Membrane through Facilitated Diffusion

Particles undergo facilitated diffusion are the particles that cannot diffuse through the phospholipid bilayer such as

1. Large particles such as glucose, amino acids, proteins and nucleic acids
2. Some ions such as the sodium ions and chloride ions

2 Types of Transport Protein

Facilitated diffusion occurs through 2 types of transport protein, namely

1. Channel Protein
2. Carrier Protein

Mechanism of Facilitated Diffusion

Click on the links below to see how facilitated diffusion happen through the plama membrane of the cell.

Concentration Gradient

Facilitated diffusion happens down a concentration gradient.

Similarities between Simple Diffusion and Facilitated Diffusion

1. Down the concentration gradient (From high concentration to low concentration)
2. No energy is required

Differences between Simple Diffusion and Facilitated Diffusion

What is Osmosis?

Osmosis is the diffusion of a water through a semi-permeable membrane, from a solution of low solute concentration to a solution with high solute concentration.

It is a physical process in which a solvent moves, without input of energy, across a semi-permeable membrane separating two solutions of different concentrations.

Important Points:

• It is the diffusion of water (normally) through a semi-permeable membrane.
• It is from a dilute solution to a more concentrated solution.

What is passive transport?

1. Passive transport is the movement of substances across the cell membrane without the use of energy by the cell.
2. During passive transport, substances move down their concentration gradient, hence no energy is required.
3. Passive transports can happen through three different channels, namely
1. lipid bilayer
2. pore protein
3. carrier protein

What is diffusion?

Diffusion is the movement of particles from a high density region to a low density region. No energy is needed and no membrane involves in diffusion.

The Dynamic Equilibrium

Diffusion will continue until the concentration in all region is the same. When this happen, we say it has reached the dynamic equilibrium.

Factors Affecting the Rate of Diffusion (How fast diffusion happens)

Particles that Move Through the Plasma Membrane Through Diffusion

1. Substances soluble in fat: fatty acid, glycerol, some vitamins (A,D,E,K)
2. Neutral particles: water, oxygen, carbon dioxide,

Example of Diffusion

Between alveoli and blood capillaries in the lung during gases exchange.

The Plasma Membrane

The plasma membrane is a semi-permeable lipid bilayer found in all cells that controls water and certain substances in and out of the cell.

Function of the Plasma Membrane

1. Protects the cell.
2. Separates the intracellular components from the extracellular environment.
3. Controls what enters and exits the cell

Necessities for the Movement of Substances across the Plasma Membrane

1. To transport nutrients into the cell.
2. For gases exchange
3. To excrete metabolic waste.
4. To maintain the pH value and ionic concentration of the cell.

Substances In and Out through the Membrane

Structure of the Plasma Membrane

Fluid Mosaic Model

Permeability of the Phospholipids Bilayer

The permeability of the phospholipids bilayer is determined by:

1. the size
2. the charge and
3. the polarity

of the substances pass through it.