Capillaries I & II Flashcards
How does metabolism affect solute exchange?
Metabolism creates concentration gradients to transport solutes and fluids for gaseous and nutrient exchange
What is the fate of O₂ , glucose, urea and CO₂ in the body?
O₂ and glucose are transported around the body
CO₂ and urea are removed
Describe the structure of cell membranes?
- consist of 2 layers of ampiphatic phospholipids
- polar phosphate heads (hydrophilic)
- non polar fatty acid tails (hydrophobic)
- form bilayers in solution
Outline the functions of cell membranes
- providing support and function
- cell to cell recognition (immune system)
- controls what enters / leaves cells
- regulates cell function (e.g. insulin mediated glucose
uptake)
How does the membrane allow us to differentiate between cells?
The various membrane functions allow us to differentiate between cells
How do membranes act as barriers to transport?
it’s difficult to get solutes across the hydrophobic centres of the membrane
How does the structure of membranes aid transporting functions?
- contains transmembrane proteins that span across the
membrane and facilitate transport and signalling - carbohydrates anchor proteins and orient them
These complicated structures are a barrier and aid
movement across the membrane
What are the different types of transport?
- passive
- active
What is passive transport?
Random movement of molecules down a gradient of:
- concentration
- pressure
- osmotic
- electrical
Passive - doesn’t require ATP
Works effectively over short distances - t is proportional to distance^2
Describe the features of passive diffusion?
Doesn’t require energy
Simple diffusion O₂ /CO₂
facilitated diffusion is via specific channels or transmembrane molecules (ions/glucose via GLUT)
What is active transport?
The movement of molecules against a gradient requiring energy (ATP)
- ATP dependent pumps, endocytosis + exocytosis
What are the different passive transport processes?
Diffusion
- conc. gradients
e. g. uptake of O₂ from lungs -> blood
Convection
- pressure gradient
e. g. blood flow from heart -> vessels
Osmosis
- osmotic pressure graident
e. g. H₂O uptake in cells
Electrochemical flux
- electrical + concentration gradient
e. g. ion flow during action potentials
Describe the structure of capillaries
Capillaries are made of endothelial cells - 1 cell thick
semi-permeable and amenable to certain types of diffusion over short distances
Where in the body are capillaries found?
Found near every cell in the body, but higher density in highly active tissues (muscle, liver, heart, kidney, brain etc.)
What is solute exchange?
Passive diffusion of O₂ , glucose, amino acids, hormones, drugs etc. between substances
What is the role of fluid exchange?
occurs along pressure gradients and regulates plasma and interstitial fluid volumes
Where does most exchange of solutes occur in the body?
Most exchange occurs at capillaries
Outline the vessel network solutes pass through
arteries branch into arterioles -> capillaries -> venules -> veins towards the heart
What is the role of capillaries in the network of vessels?
capillaries connect terminal arterioles to venules
- extension of inner lining of arterioles
What is the rate of solute transport dependent on?
Depends on properties of:
- passive diffusion (conc. , rate & diffusion)
- solutes + membranes (Fick’s Law)
- Capillaries
combining all of these provides concept of permeability
What is permeability?
How easy it is for the solute to cross the membrane
Describe the movement of molecules during passive diffusion?
Molecules move at random (due to random thermal motion) from an area of high to low concentration, eventually reaching equilibrium
When is diffusion most effective?
Great for lipid-soluble solutes over short distances e.g. O₂ / CO₂
What is the relationship between time and diffusion rate?
t ∝d² time taken (t) for one randomly moving molecule to move a net distance (x) in one specific direction increases with distance squared (d²)