Membrane Permeability

Question 1

Solute

Answer 1

Substance that gets dissolved

Question 2

Solvent

Answer 2

Liquid that does the dissolving to form a solution

Question 3

Solution

Answer 3

Solute + Solvent

Question 4

Osmosis

Answer 4

Movement of water from low solute concentration to high solute concentration

Question 5

Tonicity

Answer 5

Ability of a solution to make water move into or out of a cell by osmosis

Question 6

Hypertonic

Answer 6

SOLUTION has higher solute concentration

Water moves out of RBC (low []) to solution with high []

Shriveled up cell

Question 7

Isotonic

Answer 7

Equal solute concentration

Question 8

Hypotonic

Answer 8

SOLUTION has lower solute concentration

Water moves from solution (low solute []) into the RBC with higher []

Cell swells up

Question 9

Why is 0.15 M NaCl isotonic with the 0.3M RBC cytoplasm?

Answer 9

NaCl dissociates into 2 particles in water

NaCl (0.3) –> Na+ (0.15M) + Cl (0.15 M)

Question 10

Can NaCl cross the cell membrane? Why?

Answer 10

No. NaCl is charged (polar) and RBCs have no transporters (so slow permeability)

Question 11

Why does 0.3 M Ethylene glycol cause lysis even though the solution is isotonic?

Answer 11

The concentration of ethylene glycol is much higher outside the RBC so over time it will enter the cell

Question 12

What is lysis? What does a solution of this look like?

Answer 12

Cells take in water, swell up, and burst

A solution with lysed cells will be more transparent.

An intact RBC solution is opaque

Question 13

What are the DNA base pairings?

Answer 13

A and T
C and G

Question 14

Which base pairing has 2 hydrogen bonds?

Answer 14

A and T

A=T

It does not take as much effort to keep an apple attached to a tree so it needs less hydrogen bonds (than C and G

Question 15

What base pairing has 3 hydrogen bonds?

Answer 15

C and G

It takes more effort to keep a big car in the garage so it needs more bonds

Question 16

Purines

Answer 16

Have 2 rings (two shapes)

A and G

Pure As Gold

Question 17

Pyrimidines

Answer 17

1 ring (one shape)

C and T (and U)

CUT the Py

Question 18

From which end do we read DNA sequences?

Answer 18

From 5’ to 3’ end

Question 19

How do we distinguish between the 5’ and 3’ end

Answer 19

5’ end: Has a free phosphate group attached to the 5th carbon on the terminal sugar.
Considered the beginning or end of a sequence

3’ end: Has a free hydroxyl group attached to the 3rd carbon on the terminal sugar.
This is where new DNA is added.

Question 20

Lysis means the solute could or could not cross the membrane?

Answer 20

Lysis means the solute could cross the membrane

Question 21

What effect does temperature have on lysis?

Answer 21

Higher temps increase membrane permeability and lysis

Lower temps decrease membrane permeability and lysis

Question 22

Important note about RBC membranes

Answer 22

The RBC membrane has very few membrane proteins and none of them are transporters for the solutes/reagents we are testing

It is a good model for a phospholipid bilayer because of this

Question 23

What is the total solute concentration of an RBC cytoplasm?

Answer 23

0.3 M

Of this total concentration only a small amount (assume 0M) is NaCl and none of it is ethylene glycol

Question 24

Is ethylene glycol a salt?

Answer 24

No, so it stays intact when it dissolves unlike NaCl

Question 25

Why will ethylene glycol cross the RBC membrane but not NaCl?

Answer 25

Ethylene glycol is a small uncharged molecule that can still cross a membrane that is "impermeable to solutes" NaCl dissociates into large charged ions that get repelled by the hydrophobic part of the phospholipid bilayer

Question 26

Which statement below is correct regarding red blood cells (RBC) in a 0.3M solution of Ethylene Glycol? 1) Initially, this solution is hypertonic to the RBC. 2) Initially, this solution is isotonic to the RBC. 3)Initially this solution is hypotonic to the RBC.

Answer 26

2) Initially isotonic because to begin, no ethylene glycol has crossed the membrane and RBCs have ~0.3M

Question 27

True or false: Solutes that are more nonpolar will cause a faster lysis time, because the membrane is more permeable to them

Answer 27

True Nonpolar molecules go faster than small polar molecules which go faster than large polar molecules Larger molecules need transport proteins The hydrophobic core is non polar so like likes like

Question 28

How did we measure RBC permeability in the lab?

Answer 28

By observing RBC lysis times in solutions of varying temperatures

Question 29

How would a change in temperature increase membrane permeability?

Answer 29

Higher temperatures can disrupt the lipid bilayer, making the membrane more permeable

Question 30

When selecting the solute to use in your treatment tubes, do you think this solution should be one that causes lysis by osmosis or not?

Answer 30

Yes, we are still measuring the rate of lysis but are focusing on the impact of temperature