LAB 3 CELL MEMBRANE FUNCTION AND STRUCTURE pg.48 Flashcards
What is a Hypotonic solution?
When the total solute [ ] is lower outside than inside. So net diffusion of solute will be into the cell (lysing)
What is a Hypertonic solution?
When the total solute [ ] is higher outside than inside. So net diffusion of solute will be outside of the cell (shrivelling)
What is an Isotonic solution?
When the total solute [ ] is equal to both outside and inside of a cell causing no net movement to be made.
What is tonicity?
Tonicity is a measure of the effective osmotic pressure gradient; the water potential of two solutions separated by a partially-permeable cell membrane.
What is the difference between diffusion and osmosis?
Osmosis is the movement of water molecules through the cell. Diffusion is the movement of molecules, such as oxygen, in and out of a cell.
You place a cell in a hypertonic solution. The membrane is impermeable to all solutes present. You wait a few minutes. After this time, how might you describe tonicity?
The water will diffuse out of the cell across the membrane into the solution. The tonicity will not change because the solute cannot cross the membrane.
True or False?
Does the RBC cytoplasm have a lot of membrane proteins?
FLASE :(
RBC has very few membrane protiens.
What is the total solute [ ] of RBC cytoplasm?
0.3M
Solutes diffuse according to…
Their own concentration gradients
Water diffuses according to…
The tonicity of the solution as a whole (the concentration of all solutes present)
Why will the test solution and blood mixture become more and more transparent over time?
The red blood cells will lyse over time
What is the permeability order of lipid bilayers?
Small nonpolar molecules –> Small uncharged polar molecules –> large uncharged polar molecules –> small ions
Can ions cross membranes on their own?
No, they always need help from a membrane protein.
Do nonelectrolytes dissociate in water?
No, they do not. As a result, they are counted as 1 species.
Ex. 0.3M Ethylene Glycol is 0.3M, not 0.9M.
How do you tell if RBCs have lysed with the naked eye?
The blood will become more opaque.
Why would lysis occur when RBCs are added to a solution of distilled water?
There is a higher concentration of water outside the cell than inside the cell. Water follows its concentration gradient into the cell, causing it to lyse.
Why would RBCs in 0.3M NaCl not lyse, but RBCs in 0.3M Ethylene Glycol lyse?
Because the membrane is permeable to ethylene glycol; the tonicity will change over time, causing water to move.
Why do lysis times differ?
Because the permeability of molecules is different
What happens to RBCs in 0.3M NaCl?
Nothing. The solution is initially isotonic and, because the membrane is impermeable, the tonicity cannot change.
What happens to RBCs in 0.8M NaCl?
They will shrivel up.
This is because while the membrane is impermeable, the solution is initially hypertonic to the RBC.
As a result, the water will follow its concentration gradient out of the cell.
What is essential to know when adding blood drops to a test solution?
They need to drop directly into the bottom of each test tubes; running down the sides causes inaccuracies.
TRUE OR FLASE?
Water has a solute concentration
FALSE :(
No, because water has no solutes.
