Osmosis Flashcards
What is the size of distilled water?
Distilled water is 55.55 molar
How does solutes affect water molecules?
Solute molecules displace water molecules and decrease water concentration
What is osmole?
- It refers to the number of osmotically active particles in a solution.
- For example: 1 mole of NaCl dissociate into 2 osmoles
1 mole of glucose dissociate into 1 osmole
What is osmolarity?
It is the number of osmoles per liter.
What is osmolality?
It is the number of osmoles per kilogram.
How is osmole usually expressed?
Physiological concentration are usually expressed as millimoles
What is osmosis?
It is the movement of water across a semipermeable membrane down its concentration gradient.
What is a semipermeable membrane?
It a membrane permeable to water but not solutes.
What is osmotic pressure?
It is created by the difference in the concentration of impermeable substances across a semipermeable membrane.
- It is the pressure necessary to stop water movement.
What type of property is osmotic pressure?
It is a colligative property because it depends on the number of solute present
Why is the degree of ionization must be considered?
Because osmotic pressure depends on the number of solute.
What are other colligative properties?
They are freezing point depression, vapor pressure depression and boiling point elevation.
What factors determine osmotic pressure?
Osmotic pressure is directly proportionate with the number of particles formed by dissociation, absolute temperature and molar concentration of solute.
Give the van Hoff’s law of osmotic pressure.
TT=RTnc
At what condition does van Hoff’s law work best?
It works best at very low solute concentration.
What happens to van Hoff’s law at physiological condition?
At physiological condition and in protein-containing solutions, there is a great deal of deviation.
What are isotonic, hypertonic and hypotonic solution?
- Solutions of equal osmotic pressure is isosmotic
- A solution with higher osmotic strength than another is hyperosmotic
- A solution with lower osmotic strength than another is hypoosmotic.
What does cell volume represent?
It represents the concentration of solutes in the extracellular solution compared with the intracellular solution.
What is tonicity of a solution?
Tonicity of a solution represents its ability to influence the volume of cells immersed in it.
What effect do isotonic, hypertonic and hypotonic solutions have?
- Isotonic solution produces no change in cell volume
- Hypertonic solutions cause cells to shrink (crenate)
- Hypotonic solutions cause cells to swell or burst (lyse)
Describe the effect of permeant solutes.
The addition of permeant solute produces transient changes in cell volume since permeant solute eventually equilibrate across the membrane.
What happens when a cell is placed in a solution with only permeant solutes?
The cell will burst because the permeant solute will equilibrate but the cell is filled with osmoles and water will rush in causing lysis.
What is reflection coefficient?
It is a measure of the permeability of a membrane to a solute.
What is the range of reflection coefficient?
- Permeable solute: 0 -> effective osmotic pressure is 0
- Impermeable solutes: 1 -> effective osmotic pressure is maximum.
What happens when reflection coefficient approaches 0?
- At 1 ->maximum osmotic flow -> maximum osmotic pressure.
- Approach 0 -> decreasing osmotic flow -> decreasing osmotic pressure.
Give the equation for effective osmotic pressure.
TT= 6RTnc
How do cells response to changes in tonicity?
- Increase volume
- Degrease volume
What is regulatory volume increase?
Activated by shrinkage caused by hypertonic solution
- Acute response
- Chronic response
Explain acute response of regulatory volume increase.
- sec - min
- Increase KCl
Explain chronic response of regulatory volume increase.
- Production of impermeable organic solutes (idiogenic osmoles)
- Sorbitol or inositol
Where is regulatory volume increase popular?
Active in oligodendrocytes
Example of chronic regulatory volume increase.
Shrinkage -> produce aldose reductase catalyzes sorbitol production from glucose
What happens when chronic hypertonicity is corected too quickly?
- Cause brain edema or death cause it’s slow reducing idiogenic osmoles.
