Fluid components Flashcards
What is molar weight?
1 mole of a molecule made up to 1 litre with water
What is molal weight?
1 mole of a molecule made up with 1 litre of water
What is 1 mole of a molecule?
The molecular weight in grams
Why is molal weight used?
It is more independent of temperature
Where in our bodies is water found?
2/3 in the intracellular fluid, 1/3 in the extracellular fluid.
Some in the eye, cartilage and cervical fluid.
Within the ECF 75% in the interstitial fluid and 25% in the plasma
Why do cell membranes stop polar molecules passing through?
Hydrophobic core
Why do we assume free movement of water across the membrane?
The membrane contains aquaporins that allow free movement
Is the plasma membrane permeable to small non-polar molecules?
Yes they can cross freely
What type of molecules can cross the plasma membrane but slowly?
Small and large uncharged polar molecules
What type of molecules cannot cross the plasma membrane?
Ions
What is the electrochemical gradient and what does it require to induce movement?
Movement of charged molecules across a membrane (electrical + chemical gradient)
It still requires a concentration gradient (chemical)
What is the Gibbs-Donnan effect?
Na+ and Cl- are in equilibrium when the chemical and electrical gradients are equal.
Plasma and interstitial fluid are made of the same components except that plasma contains proteins.
These proteins have a negative charge.
This means Na+ is drawn into the plasma and Cl- is forced out of the plasma, down electrostatic gradients.
These gradients compete with the concentration gradients and at some points an equilibrium between the electrical and concentration gradients.
What does the Gibbs-Donnan effect state about the concentrations of Na+ and Cl-?
There will be more Na+ in plasma, and more Cl- in interstitial fluid but the 2 will be in equilibrium between electrical and chemical gradients
