Body fluid compartments Flashcards
What molecule assists in moving water between compartments?
Aquaporins
Through which membrane does glucose move?
Endothelium
Can electrolytes move through the endothelium?
Yes but cell membranes limit transfer
Can proteins move through the endothelium?
No, they are confined to the endothelium
How are proteins moved through the membrane?
An active process - membranes engulf the protein to form a vesicle which allows it to be deposited where it is required
How do you create a solution?
Dissolve solute in solvent
From what direction osmolarity will water move?
From low to high osmolarity
At equilibrium, which two pressures will be equal?
Hydrostatic and osmotic
How do you determine osmolarity?
The number of active particles per unit volume, not their size
What is osmolarity?
The number of osmoses of a substance in one litre of solution
What is osmolality?
Number of osmoses per kg of solvent
What pressure does 1 mole of glucose exert on a litre of water?
10 sm/L
When will one mole of a substance exert one osmole of pressure?
If the particles remain unchanged in solution and consist of 6.02 x 10^23 particles
If a solute dissociates into ions, what happens to the osmotic potential of each?
They become osmotically active
Which particles generate most of the osmolarity in body fluids?
Electrolytes
What is tonicity?
After the loss of any particles from the administered solution, the remaining osmotic pressure determines the tonicity of the original solution
Structure of the phospholipid bilayer
Semi-permeable Studded with proteins, can be full or partial thickness Hydrophilic heads Hydrophobic tails Glycoproteins
Another word for hydrophilic
Lipophobic
Another word for hydrophobic
Lipophilic
What is active movement?
Against concentration gradient
Requires energy
What is passive movement?
Down concentration gradient
No energy required
When will diffusion through a membrane increase?
High concentration gradient
Low molecular weight
High lipid solubility
Low degree of ionisation
What do aquaporins do?
Transmembraneous and allow for water to be transmitted across the lipid bilayer
What shape are aquaporins?
Narrow and hourglass shaped
Are aquaporins charged?
Yes
What peptide structure is found in aquaporins?
Peptide alpha helices
What is the main extracellular cation?
Sodium
What is the main intracellular cation?
Potassium
Characteristics of sodium/potassium pump
3 sodium ions occupy pump ATP binds to pump and phosphorylates Causes conformational change Sodium released into ECF 2 potassium ions occupy pump Potassium moved to ICF Phosphate released ADP and Pi - ATP
How is the resting membrane potential achieved by the sodium potassium pump?
Selective slow outward leak of potassium
What is the main difference between interstitial fluid and plasma?
Protein concentration
Concentration of sodium in plasma
140
Concentration of potassium in plasma
4
Concentration of calcium in plasma
2
Concentration of magnesium in plasma
1.5
Concentration of chlorine in plasma
100
Concentration of HCO3- in plasma
25
Concentration of HPO4 in plasma
2
Concentration of proteins in plasma
1.2
Concentration of glucose in plasma
5
Concentration of urea in plasma
5
What is normal plasma osmolarity?
280-290 mOsmoles/L
What is the name for the pressure created by the protein?
Oncotic
Where does excess fluid from the capillary get drained to?
The lymphatic system
How can molecules pass through the capillary endothelium?
It has small gaps
How can molecules move through the glomerulus?
Bigger pores so larger molecules can get through
How is movement across the capillary endothelium regulated?
Gaps between adjacent cells
Glycocalygeal layers above endothelium
Which molecules can fit through the capillary endothelium?
Water, electrolytes and small dissolved minerals
Which molecules can’t fit through the capillary endothelium?
Proteins and cells but this can change as part of the inflammatory response
Characteristics of the glycocalyx
A gel-like lining
Barrier to fluid loss and WBC migration
Releases nitric oxide to stimulate vasodilation
Profibrinolytic - breaks down clots
Which chemical stimulates vasodilation?
Nitric oxide
