Lecture 2-Body Fluids and Membrane Transport Flashcards
how many litres makes up a humans total body water
42
25 litres of TBW is what fluid?
Intracellular fluid (ICF)
17 litres of TBW is what fluid?
extracellular fluid
what are the three components of extracellular fluid?
interstitial fluid, plasma, transcellular fluid
13 litres of ECF is what type of fluid?
Interstitial fluid (ISF)
3 litres of ECF is what type of fluid?
Plasma
1 litre of ECF is what type of fluid?
Transcellular
Interstitial fluid
fluid that bathes the cell (tissue fluid)
Transcellular fluid
any other fluid that has been produced and crossed an epithelial membrane e.g waste from urine
6 examples of transcellular fluids
Cerebrospinal fluid (brain)
Urine (kidney and bladder)
Gastrointestinal secretions (saliva, gastric juice, pancreatic juice, bile)
Sweat
Aqueous and vitreous humours (eye)
Synovial fluid (joints)
how does fluid from the blood plasma become interstitial fluid?
electrolytes and water passes the endothelium in the capillary
what is the main difference between plasma and ISF composition
ISF contains no proteins
in order for fluid to become intracellular, what membrane does it have to pass?
plasma cell membrane
differences and similarities between ISF and intracellular fluid
electrolyte composition differs in different compartments however the osmolarity says the same
why is composition of transcellular fluid non generalisable?
electrolyte composition varies depending on what fluid
plasma-> ISF what membrane does it cross?
must cross endothelial cell layer (capillary)
ISF->ICF what membrane does it cross
plasma membrane
ISF->Transcellular fluid; what membrane must it cross
epithelium layer
why do membranes separate the compartments
to help maintain the composition of different compartments
what are the three features of the plasma membrane?
-highly selective permeability (only lipid soluble can enter and dissolve in the lipid layer, water soluble can’t enter without a transport process)
lots of transport proteins for uptake and removal of specific solutes
vital for regulation of the intracellular environment
what is the phospholipid bilayer impermeable to?
ions and polar molecules
what is permeability provided by for membrane transport?
membrane proteins (transporters)
what are the 3 membrane transporters?
channels
carriers
pumps
channels
selective for one type of ion and generally one direction
transporters
transport pairs of ions
pumps
use energy to move against the conc gradient
passive transport
driven by gradients
which transports are passive transports?
channels and carriers
active transport uses…
ATP hydrolysis
which transport mechanism uses active transport?
pumps
what are the 3 types of carriers?
facilitator/uniport
cotransporter/symport
exchanger/ antiport
uniport
facilitator
one type ion only down conc gradient in isolation (one direction)
symport
cotransporter
-two ions (usually pos and neg to maintain electrical neutrality) in same direction
antiport
exchanger
swaps one ion in for another ion out (generally the same charge to maintain electrical neutrality)
functions of transport proteins
-Uptake of nutrients, substrates, cofactors…
-export of waste products
-Regulation of intracellular ions, pH, cell volume
uptake of glucose and AAs
Uniporter picks up glucose (down conc gradient)
AAs transported usually with sodium using symport/ cotransporter
export of waste products
-Urea/ nitrogenous waste comes out the cell via uniporter
-Hydrogen ions and lactate come out using a cotransporter to rid of waste products
Regulation of intracellular ions, pH, cell volume
Regulate internal pH using exchangers e.g pH too low, rid of hydrogen ions and swap for sodium ions (antiport/ exchanger)
pH too high: swap bicarbonate ion out and chloride ion in (exchanger/ antiport)
-don’t actively transport water, use ions to generate gradient to allow water to follow
ICF vs ECF: Pottassium ions
ICF: high
ECF: low
ICF vs ECF: sodium ions
ICF: low
ECF: high
ICF vs ECF: Calcium ions
ICF: very low
ECF: low
ICF vs ECF: Chloride ions
ICF: low
ECF: high
ICF vs ECF: organic ions
ICF: high
ECF: low
ICF vs ECF: proteins
ICF: high
ECF: low
why do cells not have a water pump?
it would take too much energy/ ATP
how is water distribution determined?
by osmosis
what is the osmotic pressure at equilibrium
290
3 properties of capillary endothelium
-very thin layer of cells lining blood vessels
-highly permeable in some organs, not in others (e.g. brain)
-important role in regulation of the interstitial fluid
distribution of solutes across the capillary endothelium
ISF: low solute conc
Plasma: high solute conc as proteins can’t cross the endothelial cells or between them
what is water distribution decided by?
hydrostatic and osmotic forces
colloid
due to proteins
what happens at the arterial end of the capillary?
hydrostatic pressure> colloid osmotic pressure
-fluid is forced out of the plasma
what happens at the venous end of the capillary?
colloid osmotic pressure> hydrostatic pressure forcing fluid back into the plasma
4 features of epithelia
-layers of cells covering internal and external surfaces of organs and tissues
-protective/barrier function
-important roles in absorption and secretion
-selective
apical membrane of gut
faces inwards (centre of the gut)
basolateral membrane of gut
faces outwards
in the gut, what are the epithelial cells connected by
tight junctions which are impermeable
in the gut, what facilitates the movement of water
sodium glucose cotransporter by creating an osmotic gradient
what allows glucose to move through in the gut? where is this located?
glucose uniporter on the basolateral membrane allowing water to be absorbed to your gut
what ions facilitates the movement of water into the gut from plasma
chloride ions
role of sodium pottassium ATPase in the gut
creates a high pottassium inside and a low sodium inside the cell causing a gradient
what allows the potassium ions into the gut leading to chloride and sodium ions coming in causing water to follow and into the cell
sodium potassium two chloride cotransport
on the apical membrane of epithelial cells in the gut, what channel opens to allow water out
chloride channels allowing chloride ions to diffuse out and down the conc gradient causing water to follow
how does diarrhoea occur from food poisoning
toxins generated from bacteria open the chloride channels and allows water to pour in
role of chloride channel in cystic fibrosis
chloride channel does not open causing less water to be produced leading to sticky thick mucus as can’t move water across membrane
