Lab 1 - Cell Membranes

Question 1

What is the structure of the cell membrane?

Answer 1

Phospholipid bilayer with hydrophillic heads and hydrophobic tails

Question 2

What is the pathway across the cell membrane for lipid soluble molecules?

Answer 2

Passive diffusion = a nonselective process where any molecule able to dissolve in the phospholipid bilayer is able to cross the plasma membrane.

Question 3

What is the pathway across the cell membrane for water soluble molecules?

Answer 3

Active transport or facilitated diffusion.

Question 4

What are the normal concentrations of Na+, K+ and Cl- in the intracellular and extracellular fluid?

Answer 4

Na+: ICF 10, ECF 150
K+: ICF 150, ECF 5
Cl-: ICF 8, ECF 110

Question 5

What is Packed Cell Volume (PCV)?

Answer 5

The proportion of blood occupied by cells (also known as the haematocrit).

Question 6

What are the two types of blood cells?

Answer 6

Erythocytes = RBC
Leukocytes = WBC

Question 7

What happens to PCV when fluid moves into RBC (cell swells)?

Answer 7

Increases = the proportional of blood occupied by cells has increased

Question 8

What happens to PCV when fluid moves out of RBC (cell shrinks)?

Answer 8

Decreases = the proportion of blood occupied by cells has decreased

Question 9

What is haemolysis?

Answer 9

Destruction of RBC (they swell and then burst)

Question 10

If there is a red colour in the plasma layer what does this suggest has occurred?

Answer 10

Haemolysis

Question 11

What is the differences between molarity and osmolarity?

Answer 11

Molarity describes the molar concentration of a given solute in a solution - whereas osmolarity describes the total number of osmotically active particles in a solution.

Question 12

What is the difference between osmolarity and tonicity?

Answer 12

Toncity describes the observed effect a solution has on cell volume - it only describes the solution we put the cells in and what the solution will do to the cells - whereas osmolarity explains what happens to the cell and the solution.

Question 13

What is the effect on PCV in a hypotonic solution?

Answer 13

PCV increases as cells swell

Question 14

What is the effect on PCV in a hypertonic solution?

Answer 14

PCV decreases as cells shrink

Question 15

Does a solute with a higher molecular weight reach haemolysis faster or slower and explain why?

Answer 15

Slower - takes longer for particles to pass through the lipid bilayer.

Question 16

What solutions do not dissociate?

Answer 16

Glucose and Urea

Question 17

Urea does not dissociate but can cause heamolysis - explain why?

Answer 17

There is a urea transporter