Fluid Compartments & Membrane Transport Flashcards
Four most common elements in the human body? % body weight?
C - 18%
H - 10%
O - 65%
N - 3.4%
Minerals - 3.6%
Seven most common minerals in the body?
Calcium, Iron, Magnesium, Phosphorous, Sodium, Potassium, chlorine
What makes up the 30% of lean body tissues that isn’t water?
Carbohydrates, Protein, Lipids, Nucleic acids built from sugars, amino acids, fatty acids and nucleotides respectively
Define hydrophilic and give examples
Polar, dissolve readily in water. Glucose, ethanol, NaCl-
Define hydrophobic and give examples
non-polar, insoluble in water. Fats and cholesterol
Define amphiphilic and give examples
A molecule with mixed properties, with some parts polar and other non-polar. Phospholipids and bile-salts
Difference between intra/extracellular water and fluid
fluid includes solutes in the body water
How is extracellular fluid divided?
Into plasma (liquid component of blood) and interstitial fluid (lies outside blood vessels and bathes cells)
Distribution of body water in a 70Kg man
28L intracellular water, 10.4L interstitial water, 2.8L in plasma, 0.8L transcellular water
What is the diffusion coefficient?
A physical constant reflecting the affects of the molecular characteristics of various molecules on their rate of diffusion. depends on temperature and gets smaller as molecule size increases
What is Fick’s law?
Amount moved = diffusion coefficient * area * concentration gradient OR J = -DA(dC/dx)
Define osmotic pressure
equal to the min. hydrostatic pressure required to prevent movement of water across a membrane from a solution of lower solute conc. to higher
Define an Osmole
An osmole (Osm) is a unit that measures the number of moles of solute particles that contribute to osmotic pressure in a solution.
It’s based on how many particles a compound dissociates into in solution.
For example:
1 mole of NaCl becomes 2 osmoles (Na⁺ and Cl⁻).
1 mole of glucose stays 1 osmole (because it doesn’t dissociate).
Define osmolarity
osmoles per litre of solution
Define osmolality
osmoles per Kg of water. used in biology and med as volume is temperature dependent, mass isn’t.
Total osmolality
sum of osmolality due to each individual solute
Equation for osmotic pressure
The osmole is tied to osmotic pressure via this formula:
Π = 𝑖𝑀𝑅𝑇
no. particles per formula unitMolarity
Define oncotic pressure
the osmotic pressure exerted by blood plasma proteins. small contributor to overall osmotic pressure of blood, but important as intr/extracellular fluid usually iso-osmotic
Define tonicity
refers to the influence of osmolality on volume of cells.
Cells placed in isotonic solution don’t change volume. In hypotonic solutions they swell, potentially to the point of osmolysis. Cell crenate (shrivel) in hypertonic solutions.
Why iso-osmotic doesn’t equal isotonic
if cells are placed in an iso-osmotic solution of urea (can diffuse across membrane), urea can diffuse into cells, decrease osmolarity and osmotic pressure, so fluid moves into the cells until they burst - hypotonic.
How to measure plasma volume of a patient?
Example:
Inject 10ml of a 1% (100mg) solution of Evans Blue dye into the patient (high affinity for serum albumin). After 5 mins a blood sample taken has a conc. of 0.037 mg dye per ml blood. As volume = mass/conc.: 100/0.037 = 2702 ml
Define electrochemical gradient
governs the flow of any ion across the plasma membrane via ion channels. Reflects concentration gradient, membrane potential and ion charge. Also the difference between equilibrium potential for the ion and membrane potential
Properties of ion channels
- central pore for diffusion
- passive down electrochemical gradient
- selective for specific ions
- high capacity
- usually named after ion
- leak or gated (open all the time or stimulated)
Properties of carrier proteins
- bind to molecule, conformation shape change, moves molecule across
- transport small organic molecules as well as ions
- stereoselectivity
- less capacity leading to saturation
- capacity for active transport - often using cotransport
- uniport, symport, antiport
