Lecture 3 Flashcards
What determines cell shape? Give examples of different cell types.
The cell type and its function.
E.g. Sperm cell, skin cell, nerve cell, striated muscle cell, non-striated, red blood cells.
What does the cytoskeleton do?
The cytoskeleton supports cell shape and enables cell movement. However, it is NOT rigid, unlike bones.
Why does cell water movement have to be controlled?
Cells can easily shrink or swell as a result of water exiting or entering the cell. In extremes this can lead to cell death.
Are cell membranes permeable to water?
Yes, highly.
Are there any active water transport mechanisms?
No, all water transport is passive.
How can cells maintain water homeostasis?
Osmotic pressure
What is osmotic pressure?
This is the pressure generated when two compartments separated by a semi-permeable membrane contain different solute concentrations.
How does the osmotic pressure for solutions of small molecules differ?
It depends solely on the concentration of solutes, rather than the mass or charge.
What is Van’t Hoff’s law?
π (Pi) = nCRT
Osmotic pressure = number of dissociable particles * total concentration * gas constant * temperature (K)
What is osmolarity?
Osmolarity is the number of osmoles of solute per 1L of solvent (Osm/L)
What is osmolality?
Osmolality is the number of osmoles of solute per 1kg of solvent (Osm/kg)
What is osmolality generally given as in Biology?
Usually given as (mOsm/kg H2O) :
milliosmoles per kg of water.
What does Van’t Hoff’s law apply to? Why these?
Small molecules. Proteins and other large molecules in solution produce a larger osmotic pressure than expected.
What is oncotic pressure?
The osmotic pressure caused by proteins.
What is Tonicity and what is it equal to?
Tonicity is the effective osmolality and is equal to the sum of the concentrations of the solutes which have the capacity to exert an osmotic force across the membrane.
