LAB 3 CELL MEMBRANE FUNCTION AND STRUCTURE pg.48

Question 1

What is a Hypotonic solution?

Answer 1

When the total solute [ ] is lower outside than inside. So net diffusion of solute will be into the cell (lysing)

Question 2

What is a Hypertonic solution?

Answer 2

When the total solute [ ] is higher outside than inside. So net diffusion of solute will be outside of the cell (shrivelling)

Question 3

What is an Isotonic solution?

Answer 3

When the total solute [ ] is equal to both outside and inside of a cell causing no net movement to be made.

Question 4

What is tonicity?

Answer 4

Tonicity is a measure of the effective osmotic pressure gradient; the water potential of two solutions separated by a partially-permeable cell membrane.

Question 5

What is the difference between diffusion and osmosis?

Answer 5

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.

Question 6

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?

Answer 6

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.

Question 7

True or False?
Does the RBC cytoplasm have a lot of membrane proteins?

Answer 7

FLASE :(
RBC has very few membrane protiens.

Question 8

What is the total solute [ ] of RBC cytoplasm?

Answer 8

0.3M

Question 9

Solutes diffuse according to…

Answer 9

Their own concentration gradients

Question 10

Water diffuses according to…

Answer 10

The tonicity of the solution as a whole (the concentration of all solutes present)

Question 11

Why will the test solution and blood mixture become more and more transparent over time?

Answer 11

The red blood cells will lyse over time

Question 12

What is the permeability order of lipid bilayers?

Answer 12

Small nonpolar molecules –> Small uncharged polar molecules –> large uncharged polar molecules –> small ions

Question 13

Can ions cross membranes on their own?

Answer 13

No, they always need help from a membrane protein.

Question 14

Do nonelectrolytes dissociate in water?

Answer 14

No, they do not. As a result, they are counted as 1 species.

Ex. 0.3M Ethylene Glycol is 0.3M, not 0.9M.

Question 15

How do you tell if RBCs have lysed with the naked eye?

Answer 15

The blood will become more opaque.

Question 16

Why would lysis occur when RBCs are added to a solution of distilled water?

Answer 16

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.

Question 17

Why would RBCs in 0.3M NaCl not lyse, but RBCs in 0.3M Ethylene Glycol lyse?

Answer 17

Because the membrane is permeable to ethylene glycol; the tonicity will change over time, causing water to move.

Question 18

Why do lysis times differ?

Answer 18

Because the permeability of molecules is different

Question 19

What happens to RBCs in 0.3M NaCl?

Answer 19

Nothing. The solution is initially isotonic and, because the membrane is impermeable, the tonicity cannot change.

Question 20

What happens to RBCs in 0.8M NaCl?

Answer 20

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.

Question 21

What is essential to know when adding blood drops to a test solution?

Answer 21

They need to drop directly into the bottom of each test tubes; running down the sides causes inaccuracies.

Question 22

TRUE OR FLASE?
Water has a solute concentration

Answer 22

FALSE :(
No, because water has no solutes.