Lab 3 Flashcards
Selectively permeable
-semipermeable membrane
-only allows certain molecules to pass through it, while excluding others
-is partly related to the size of the submicroscopic pores which are present
> Large molecules may be very slow or blocked
> water can move freely
Diffusion
- as the movement of molecules from a region of high concentration to a region of lower concentration until a state of equilibrium is reached
- the respiratory gases (oxygen and carbon dioxide) move across cell membranes by diffusion.
- ex: if table salt (NaCl) is dissolved in water, the salt dissociates and its ions disperse throughout the water molecules until a uniform solution results
Osmosis
- diffusion of water molecules through a cell membrane from a region of high contentration to low
- the diffusion of water molecules through a selectively permeable membrane
The dialysis tubing
- permits the passage of small molecules such as iodine
* restricts the passage of large molecules such as starch
Dialysis Experiment:
1)
-iodine solution in a beaker (has a high [ ] of water molecules (a dilute solution).)
- starch solution in a dialysis bag (has a low [ ] of water molecules (a more concentrated solution).)
2)
- iodine solution in a dialysis bag (has a high [ ] of water molecules (a dilute solution).)
- starch solution in a beaker (has a low [ ] of water molecules (a more concentrated solution).)
1)
- water moved into the bag
- iodine moved into bag
- bag with starch turned blue
- outside remained clear
- no starch movement
2)
- water moved out
- iodine moved out
- outside beaker turned darker blue
- bag remained clear
- no starch movement
Why must a cell maintain proper water levels?
This situation can alter a cell’s internal volume of water, producing either a net gain or a net loss of water by the cell. As gaining water may cause a cell to swell and burst and losing water may cause a cell to shrivel and die,
Tonicity
a measure of the solution’s ability to change the shape of cells by affecting the cells’ internal water volume.
Isotonic
- iso means “the same”
- A cell placed in an isotonic solution will maintain its normal shape and volume.
Hypotonic
- hypo means “below” [hypo = hippo fat]
- A solution that contains a lesser concentration of dissolved particles and a greater concentration of water molecules than the cell
- water molecules enter the cell faster than they leave and the cell SWELLS
- water molecules will flow by osmosis from the area of greater water concentration (outside the cell) to the region of lesser water concentration (inside the cell)
Hypertonic
- hyper means “above” [hyper = active skinny]
- A solution that contains a greater concentration of dissolved particles and a lesser concentration of water molecules than the cell
- water molecules move out of the cell faster than they enter, causing the cell to SHRINK
- Water will flow by osmosis from the area of greater water concentration (inside the cell) to a region of lesser water concentration (outside the cell).
Quail eggs Experiment - PRE EXPERIMENT
- 5% acetic acic -remove the calcium carbonate shell
- The two membranes provide an efficient defense against bacterial invasion and are made partly of keratin protein
- Prior to the start of the experiment, the membrane bound egg is stored in a 28% sucrose “holding solution” which is isotonic to the egg contents
Quail Egg Experiment
De-calcified egg soaked in 42% sucrose solution
- Lost 1.9g
- Placed into a hypertonic solution and lost water/shrivelled
De-calcified egg soaked in water
- Gained 1.5g
- placed into a hypotonic solution and gained water/expanded
Volume Changes in Red Blood Cells
Hypotonic solution
- Ex: distilled water
- RBC begins to increase in size
- At a certain volume, the cell membrane ruptures and the contents of the red blood cell are released
- bursting called hemolysis
Hypertonic solution
- Ex: salt solution
- RBC begins to shrink in size
- The cell tends to shrink and lose its characteristic shape,
- shape loss/shrinking called crenation
Hemolysis
Bursting of RBC due to being placed into hypotonic solution
undergoes hemolysis or hemolyzes
*only for RBC
Crenation
Shrinking/loses shape of RBC due to being placed into hypertonic solution
undergoes crenation or it crenates
*only for RBC
