Body Fluid Compartments Lecture Flashcards
05/11/24
Describe the composition of the blood
Approximately 5L, 7% of total body weight.
This is made of ECF (plasma) and ICF (fluid in RBC)
Sometimes it’s considered it’s own compartment because it’s contained in it’s own chamber - the circulatory system.
What is the extracellular fluid compartment?
The ECF is 14L, around 20% of the body weight.
3L of this is plasma in the blood and 11L is interstitial fluid. These both exchange substances through a highly permeable capillary membrane. Most proteins are too big to permeate so they stay in the plasma.
What is the intracellular fluid compartment?
28L, and 40% of the body weight.
Separated from the ECF by a membrane permeable to water, but not electrolytes.
Low Na+ and Cl-, and high K+ and proteins are important for physiological processes.
What are the ideal concentrations for Na+K+, and Cl- in the ICF and ECF?
ICF (mM): Na+ (15), Cl- (5), K+ (140)
ECF (mM): Na+ (140), Cl- (110), K+ (5)
The membrane is crucial for maintaining these concentrations
How does the ‘cell’ identify as a body compartment?
The lipid bilayer defines each cell, and controls substance movement.
What different sorts of transport does the lipid bilayer/cell membrane allow?
Free transport, Restricted transport, and Selectively permitted transport
What different sorts of membrane proteins are found in/on the cell membrane/lipid bilayer?
Integral, Peripheral or Lipid anchored.
Outline the structure of a phospholipid
They are amphipathic - they have both hydrophobic and hydrophilic properties.
Phospholipids are made of a hydrophilic phosphate head with a glycerol molecule embedded and 2 hydrophobic fatty acid chains/tails, where one is saturated and one is unsaturated.
What is the composition of the cell membrane?
55% Protein
25% Phospholipid
13% Cholesterol
4% Other lipids
3% Carbohydrate
What are the types of lipids that can be found in the membrane/lipid bilayer?
Phospholipids, Sphingolipids, Cholesterol
What are phospholipids?
Structures that form the lipid bilayer.
What are sphingolipids?
Contain amino alcohols and have hydrophobic/philic properties in most membranes.
What is cholesterol?
Dissolved in the membrane and contributes to fluidity.
Which proteins are involved in transport across the membrane?
Channel proteins, carrier proteins.
What are channel proteins?
Allow free movement of water, and other molecules/ions.
Usually selective for a particular molecule.
What is a carrier protein?
They bind to molecules, and move them through the protein to cross the bilayer.
Usually selective for a particular molecule.
What are the sorts of membrane transport?
Active → Primary (direct use of energy source) and Secondary (indirect use of energy source) active
Passive (no energy needed)
Which factors influence the rate of transport across the membrane?
Pressure, electrical potential and concentration
What is the rule of net diffusion and concentration difference?
The rate of net diffusion is proportional to the concentration difference across the membrane.
How does electrical potential affect the movement of ions across the membrane?
Electrical potential drives the movement of ions to the opposite pole, even against a concentration gradient.
How does pressure affect the movement of molecules across the membrane?
The pressure difference increases the force of molecular motion. Increased energy causes net increase in movement from an area of high pressure to an area of low pressure.
What is the permeability co-efficient?
The rate of movement of molecules in cm/sec.
What is osmosis?
The movement of water molecules across a selectively-permeable membrane.
Osmotic pressure is measured in mmHg. Water diffuses from a low solute concentration to a high solute concentration.
What is tonicity?
The mechanical effects on a cell (shrinking/swelling) - caused by placing cells in solution.
What is an isotonic solution?
Where the concentration in the ICF = ECF.
What is a hypertonic solution?
One that causes the cell to shrink.
What is a hypotonic solution?
Most common in the blood, causes RBCs to swell, and increases potential risk of bursting - dangerous.
