Water and Ion balance Flashcards
What is the extracellular fluid made of?
80% interstitial fluid and 20% plasma
What is the main extracellular cation?
Sodium
What is the main intracellular cation?
Potassium
What is the main extracellular anion?
Chloride
What are the 5 ions that are super important for ion balance?
Sodium, potassium, chloride, magnesium, calcium
What is osmolarity?
The number of moles of a solute that contributes to the osmotic pressure of a solution
What is the osmolarity of sea water?
1000 mOsM
What is the osmolarity of freshwater?
50 mOsM
What is tonicity?
Properties of an extracellular solution of impenetrable solutes that determine if water will move into or out of a system (a cell), measures the osmotic pressure gradient between 2 solutions
Why do cells act as osmometers?
They swell or shrink in response to osmotic gradients but can regulate their transport to maintain a constant volume
What happens to a cell in a more dilute solution? How does the cell get its volume back to normal?
(hypotonic solution) Water enters the cell through osmosis and the cell swells up. A cell will export solutes to get some of the water to leave
What happens to a cell in a more concentrated solution? How does the cell get its volume back to normal?
(hypertonic solution) Water leaves the cell through osmosis and the cell shrinks. A cell will import solutes to get some water to come in
Do only inorganic ions contribute to osmotic gradients?
No, cells will also alter their organic solute concentration to regulate their volume
What happens to the amount of organic solutes in the intracellular fluid if osmotic pressure increases?
Increases
What does the Ussing chamber do?
Tests ion transport across a semipermeable membrane by manipulating the chemistry on one side and measuring transport
What does an Ussing chamber experiment tell us about the transporters on the membrane?
Which side of the cells the transporters are on and if the transport is active or passive
What were the 5 results obtained from Ussing and Huf’s experiment with the Ussing chamber and the frog skin?
- Sodium transportation happens against the concentration gradient
- Na+ transport is blocked if ATP metabolism is blocked
- Transport is temperature dependent
- Transport shows saturation kinetics
- Transport is solute specific
What 2 chemicals inhibit ATP metabolism?
Ouabain (blocks ATPase function), and cyanide (blocks oxidative phosphorylation)
What were the 3 conclusions drawn by Ussing and Huf after their experiment with frog skin in an Ussing chamber?
- Ouabain inhibited transport on the basolateral side, but not the apical side, so the ATPase was only present on the basolateral side
- K+ ions are present on the basolateral side but not on the apical side, not necessary there
- Na+ saturation kinetics only exist on the apical side, only carriers there instead of ATPases
Which membrane are Na+ carriers and channels located on?
Apical
Which membrane is the Na+/K+ ATPase located on?
Basolateral
What is the difference between obligatory and controlled osmotic changes?
Obligatory changes come from the environment and we can’t control them, controlled osmotic changes are caused by active transport and are homeostatic mechanisms
What are 4 things that cause obligatory osmotic changes?
- Metabolic water production
- Diffusion across epithelium
- Defecation
- Ingestion
What does the water transport need to be to maintain homeostasis?
Input needs to equal output
