Lecture 7 - Solute and Water Flashcards
what is the fluid breakdown in the body?
a 70kg man
60% water - 42L is total body water
2/3 of TBW is ICF - intracellular fluid - in cells
1/3 of TBW is ECF - extra cellular fluid
ECF is made of
75 - 80% interstitial water - water around cells
20 - 25% is 3.5 L blood plasma, lymph and 2L red cells (the circulating volume)
what is the ion distribution between the different sections of water
osmolality is the same for plasma, interstitial and ICF
290- 310 mOsm
K+ is high in ICF
Na + is high in the ECF
interstitial - bordered by epithelial cells
Plasma - bordered by capilliary endothelium
ICF - bordered by Plamsa membrane
all of these are semi permeable membranes that water can diffuse across
what is a cell membrane for ?
it is the boundary between inside and outside of cell
it provides a partially permiable membrane
allows carbs, ions, water, amino acids ect in
waste , amonia, co2 out
it is formed of a lipid bilayer
what can get through the lipid bilayer
fats and other lipids can diffuse through
hydrophobic molecules and small uncharged molecules also diffuse through
large molecules and ions need ion channels to get through
what are the forms of passive transport ?
no energy is needed, moves down a concentration gradient
diffusion
facilitated diffusion - high to low conc, passive, uses channels, quicker than diffusion
an example are ion / voltage gated channels, only open with a stimuli
Osmotic pressure -
what is active transport ?
requires atp , usually a membrane channel of some sort
movement against concentration gradient
vesicular transport is active (phagocytosis and pinocytosis)
the moving of molecules in and out of cells,
exocytosis and endocytosis, sometimes uses cellular recptors
molecules are moved against a concentration gradient with ATP
uses a protein pump
Na+/K+ with ATPase is an example
what is flux ?
rate of flow of an uncharged solute due to diffusion is directcly proportional to the rate of change of concentration with distance in direction of flow
ie diffusion rate is dependent on distance of membrane
wider membrane, diffusion takes longer
if conc gradient of a substance is 0 , the system is in dynamic equilibrium, net flux is also 0
diffusion is….?
proportional to surface area of barrier
inversely proportional to its thickness
concentration gradient across a membrane is the driving force for net diffusion
solute movement across a bilayer occurs via simple diffusion
it is ?
movement is downhill and passive
what directs the movement of water ?
osmosis
hypertoninc - less water, more solute
isotonic - equal solute and water
hypotonic - more water, less solute
osmosis is diffusion of water, from hypotonic solution to hypertonic solution
what are aquaporin channels ?
they are integral membrane proteins
a channel for the transport of water
allow for rapid diffusion of water
they have 6 trans-membrane alpha helix proteins
hydrophillic inner cavity
there are positive residues in the center to prevent the movement of small ions like H+ , this wont disrupt H+ ion gradients int ATP production
water molecules line up and pass single file through the hydrophillic channel - 10000 molcules per min
this is still osmotically driven and depends on solute concentration gradient
