Week 5 - LAB Diffusion and Osmosis

Key Terms:

• Solution - homogenous mixture of two or more substances
• Solute - A substance which is dissolved
• Solvent - the substance in which a solute is dissolved
• Intracellular fluids - fluids found within a cell
• Extracellular fluids - fluids found outside of a cell
• Diffusion - the movement of molecules in solution from areas of high concentration to areas of lower concentration
• Concentration gradient - the change in molecular density over a given area
• Simple diffusion - small polar molecules pass through a selectively permeable membrane without assistance from areas of high concentration to areas of lower concentration
• Facilitated diffusion - large, charged molecules pass through specialized channels from areas of high concentration to low concentration
• Active transport - Molecules are moved through channels against the concentration gradient using ATP as the energy source for transport.
• Osmosis - describes the movement of water molecules across a selectively permeable membrane
• Tonicity - describes the solute differences between solutions and determines the net direction of water molecule movement
• Hypertonic - A solution with a higher solute concentration than the solute concentration on the opposite side of the permeable membrane. Hypertonic Solution has a lower percentage of water than solute.
• Hypotonic - A solution with a lower solute concentration than the solue concentration on the opposite side of the permeable membrane. Hypotonic Solution has a higher percentage of water than solute
• Isotonic - A solution with equal solute concentration on both sides of the permeable membrane.
• In osmosis, water flows from - hypotonic to hypertonic solutions
• Water potential - The tendency of water to leave one place in favor of another.
• Water always moves - from an area of higher water potential to an area of lower water potential
• The more negative the water potential - the higher the concentration of solutes in the system
• Crenate - shrink
• In most biological systems cells are - hypertonic and extracellular water flows into them
• Lyse - burst
• What happens to cells placed in pure water - they lyse due to the increase of pressure from water moving in

Exercise 1

Part I

1. Lymphocyte - Appears dark purple and enlarged with a purple halo
2. Neutrofil - Appears light purple with three dark purple spots inside
3. Hypotonic red blood cell - Appears uniform purple with no ‘donut’ visible.
4. Hypertonic red blood cell - Appears irregular in shape, non-circular
5. Isotonic red blood cell - Uniform in shape, circular with clear ‘donut’ shape visible

Part II - Blood Cells in Distilled Water

• Majority of cells appear hypotonic and enlarged with few appearing to have a regular shape.

Part III - Blood Cells in 0.9% salt solution

• Majority of cells appear to have regular shape with no defects present.

Part IV - Blood cells in 12.5% salt solution

• Cells appear to be severely damaged showing no uniform shape and signs of hypertonicity