Osmosis and Concentration Gradient

Osmosis

Osmotic Pressure

• Osmotic pressure is the pressure that develops in a solution when it is separated from a pure solvent by a semipermeable membrane.
• It is the pressure required to prevent the flow of solvent into the solution through the membrane.
• Osmotic pressure is directly proportional to:
  • Concentration of solute
  • Temperature
• Measured in atmospheres (atm) or pascals (Pa)

Concentration Gradient

• A concentration gradient is a gradual change in the concentration of a substance from high to low.
• In osmosis, a concentration gradient drives the movement of solvent molecules from an area of high concentration to an area of low concentration.
• Concentration gradient can be described in terms of:
  • Hypertonic: high solute concentration
  • Hypotonic: low solute concentration
  • Isotonic: equal solute concentration

Isotonic Solutions

• Isotonic solutions have the same concentration of solutes as the cell's internal environment.
• No net movement of solvent occurs between the cell and the solution.
• Examples:
  • 0.9% saline solution (NaCl) is isotonic with human blood
  • 5% glucose solution is isotonic with some bodily fluids

Diffusion

• Diffusion is the random movement of particles from an area of high concentration to an area of low concentration.
• Diffusion occurs in both directions, but the net movement is always from high to low concentration.
• In osmosis, diffusion of solvent molecules through the semipermeable membrane helps to equalize the concentration gradient.

Osmosis

Osmotic Pressure

• Osmotic pressure develops when a solution is separated from a pure solvent by a semipermeable membrane.
• It's the pressure required to prevent solvent flow into the solution.
• Osmotic pressure is directly proportional to concentration of solute and temperature.
• Measured in atmospheres (atm) or pascals (Pa).

Concentration Gradient

• A concentration gradient is a gradual change in solute concentration from high to low.
• Drives solvent movement from high to low concentration in osmosis.
• Concentration gradient can be described as:
  • Hypertonic: high solute concentration
  • Hypotonic: low solute concentration
  • Isotonic: equal solute concentration

Isotonic Solutions

• Isotonic solutions have the same solute concentration as the cell's internal environment.
• No net solvent movement occurs between the cell and the solution.
• Examples of isotonic solutions:
  • 0.9% saline solution (NaCl) is isotonic with human blood
  • 5% glucose solution is isotonic with some bodily fluids

Diffusion

• Diffusion is the random movement of particles from high to low concentration.
• Occurs in both directions, but net movement is from high to low concentration.
• In osmosis, solvent molecules diffuse through the semipermeable membrane to equalize the concentration gradient.

Osmosis

Facilitated Diffusion

• Facilitated diffusion is a type of passive transport that involves the movement of molecules down their concentration gradient through a transport protein.
• This process requires no energy input and is specific to certain molecules.
• It increases the rate of diffusion of certain molecules across the cell membrane.
• Examples of molecules that use facilitated diffusion include glucose, amino acids, and ions.

Diffusion

• Diffusion is the random movement of molecules from an area of higher concentration to an area of lower concentration.
• This process continues until equilibrium is reached, where the concentration of molecules is uniform throughout.
• Diffusion can occur through a cell membrane or across a distance.
• There are two types of diffusion:
  • Simple diffusion: movement of molecules through a cell membrane without the aid of transport proteins.
  • Facilitated diffusion: movement of molecules through a transport protein.

Osmotic Pressure

• Osmotic pressure is the pressure that develops in a solution when it is separated from another solution by a semipermeable membrane.
• The pressure is caused by the movement of water molecules from an area of higher concentration to an area of lower concentration.
• Osmotic pressure is measured in units of pressure (e.g. atm or kPa).
• There are three types of osmotic pressure:
  • Isotonic: the osmotic pressure of the solution is equal to that of the cell, resulting in no net movement of water molecules.
  • Hypotonic: the osmotic pressure of the solution is lower than that of the cell, resulting in water molecules entering the cell.
  • Hypertonic: the osmotic pressure of the solution is higher than that of the cell, resulting in water molecules leaving the cell.