Why can’t albumin fit through the plasma membrane?
- (-) charge
2. size
What are cells that lack direct communication with external environment? And what do they do?
- heart and blood vessels: deliver O and nutrients
- liver and kidneys: remove wastes and toxins
- N.S.: monitor and regulate the organ system
**semi permeable membranes are what keep these systems separate
what is the equation for total body weight?
TBW= ECF (33%) + ICF (67%)
ECF: is made up of blood plasma and interstitial fluid which bathes cells
ICF: intracellular fluid
what is the volume of distribution?
the total volume that substance distributes after injection
-this is totally dependent upon the property of the substance
what are the different body compartments and what separates them?
blood plasma—BLOOD CAPILLARY WALLS—>interstitial fluid—CELL MEMBRANES—> Intracellular fluid
dilution principle and tracers
this principle can be used to determine the SIZE of a fluid in a compartment
-one uses the tracer because it distributes uniformly into the compartment of interest
what does tritium oxide measure?
total body weight
what does mannitol measure?
ECF
what does evans blue dye measure?
plasma
age/organs and water content
- water content decreases with age
- and different organs have different water contents kidney and heart have a lot
what is whole blood volume?
cells + plasma (ECF)
what is hematocrit?
% of blood vol. made up by cells
~40-50%
how does one derive total blood volume?
TBV= plasma volume x100/ (100-hematocrit)
what is simple diffusion?
when MEMBRANE PERMEABLE solutes move from high concentration to low [ ]
- only small and uncharged
ex: O2, CO2, NO, water
what is facilitated diffusion?
- only transport solutes DOWN an gradient
- no energy
- use transporters
ex. RBC–glucose transporters: only if [ ] outside is greater than inside ONLY IN RBCs
* *aquaporins–move water more rapidly through membrane
what is primary active transport?
- transport AGAINST gradient
- energy is required (ATP)
ex. Ca-ATPase
what is the Na-K-ATPase Transporter? What does this have to do with osmolarity?
- it is present in all cells
- 3 Na out of cell
- 2 K into the cell… making the cell slightly negative
- because there is more negative charge inside the cell, there may be more osmotically active particles in the cell than out
- This transporter is very important for reducing osmotic particles inside the cell –> so that they don’t burst!
What is secondary active transport?
- energy isn’t DIRECTLY linked to ATP
- uses one gradient to power another
What is co transport?
aka symport
- it is a type of secondary transport
- both molecule are moving in the same direction
ex. Na–amino acid transporter
Na–glucose transporter: this pump works no matter what the glucose [ ] is outside of the cell
What is counter transport?
- antiport
- type of secondary
- moving in opposite directions
ex. Ca-Na exchanger
Osmosis
- bilayer membranes are permeable to water
- flow of water from low to high [solutes]
- movement is due to differences in osmotic pressure between the 2 compartments
What is osmotic pressure? How is it calculated?
=the pressure that would be needed to externally prevent migration of water across the membrane
-it is a colligative property
=gCσRT
g=# particles
C= concentration
σRT=a constant
What is Osmolarity? What is it determined by? What is the normal for body fluids?
-determined by the # of dissolved solute particles
= the [ ] of all particles
-Na is a major player in determining this of ECF
-ALL body fluids have the same ~290 mOsm/L
what is a reflection coefficient?
σ
- it is dependent upon what the membrane deflects back
- water can move through so for water its 0
- albumin cannot move through so for that its 1
- it is dependent on size AND charge
