Mass transport Flashcards
Describe the structure of haemoglobin
Globular, water soluble. Consists of 4 polypeptide chains each carrying a haem group which contains a ferrous ion
Loading and unloading O2
loading - hb binds w/ O2 in lungs
unloading - hb releases O2 in tissues
note: hb w/ high affinity for O2 associates more readily
Role of haemoglobin
To transport oxygen
- must readily associate/disassociate at diff. locations
- must change its affinity for O2 eg. changes shape in presence of CO2
How does saturation of O2 affect haemoglobin affinity?
After binding w/ first O2 mol, hb changes shape to make binding w/ other O2 mols easier (positive cooperativity), increasing affinity.
As hb becomes more saturated, chance of O2 binding decreases, lowering affinity
How does pCO2 affect oxygen dissociation curve?
higher pCO2, hb unloads more readily
due to hb binding more readily to H+ ions from dissociated carbonic acid than to O2, lower pH
Explain why oxygen binds to haemoglobin in lungs
- high pO2
- low conc. of CO2 in lungs so high affinity
- positive cooperation as binding takes place
Relate structure of chambers to their function
Atria: thin walled + elastic so stretches when it collects blood
Ventricles : thicker muscular wall to pump blood under high pressure to rest of body
List valves in the heart + state function of valves
bicuspid (left a.v)
tricuspid (right a.v)
semi-lunar
to prevent backflow of blood when ventricles contract and relax
What causes a myocardial infarction?
Blockage of coronary arteries, causing cells to die as they cannot respire without O2
Diastole (relaxation)
- atria fill w blood so pres. rises
- when atria pres > vent pres, a.v valves open so blood passes to ventricles -> muscle relaxes
- vent. walls relax -> recoil + reduces pres in ventricle
- vent pres < arterial pres so semi-lunar valves close
Atrial systole (contraction)
- contraction of atrial walls + recoil of relaxed vent walls
- forces remaining blood into ventricles
Ventricular systole (contraction)
- vent walls contract increasing pres, forcing a.v valves shut
- vent pres > arterial pres so semi lunar valves open, blood forced into arteries
- thick muscular wall creates high pressure needed to reach extremities
How are valves designed?
tough, but flexible fibrous tissue in cusp shapes
pressure > concave side: flaps push together
pressure > convex side: flaps move apart
Artery structure related to function
- thick muscle layer -> smaller arteries can be constricted/dilated to control vol of blood
- thick elastic layer -> stretches + recoils to maintain high pressure + smooth pressure surges
- thick wall - > resists bursting
Arteriole structure related to function
- v. thick muscle -> constriction of lumen, controlling blood movement into capillaries
- thinner elastic layer -> lower pressure to maintain
Vein structure related to function
thin muscle layer -> constriction does not control flow
thin elastic layer -> pressure to low to create recoil or burst vessel
thin wall -> can be flattened to aid flow of blood
valves -> prevent backflow when low pressure
Capillary structure related to function
- single celled endothelium -> short diffusion path
- highly branched -> large SA for exchange
- narrow lumen -> r.b. cells squeezed flat to side of capillary to be closer to cells
- spaces in endothelium -> white blood cells can escape to fight infection
Tissue fluid
Fluid containing glucose, a.acids, f.acids, dissolved ions + O2. Supplies these to tissues and removes waste
Formation of tissue fluid
- hydrostatic pressure forces fluid out of tiny gaps in capillaries (ultrafiltration)
- net movement is out despite some fluids moving back in due to their h. pressure
- Osmosis due to water pot. gradient set up by plasma leaving, H2O moves down gradient into capillaries
- Fluid returns at venous end as hydrostatic pressure drops
Explain the transpiration pull
- Water pot. in leaves is very low as water evaporates.
- Water pot. at bottom of plant v. high as water absorbed by osmosis
- difference in water pot. sets up gradient
- water moves down gradient in xylem in continuous chain
How is the transpiration pull aided by cohesion and tension?
cohesion - water is able to form continuous column, due to H bonds between water mols, that is transported
tension - negative pressure at top of plant helps pull up water from roots
Structure of xylem
- dead cells -> empty inside so more space for water
- cell strengthened by lignin -> structural support + prevents collapse due to tension
- pits -> allow lateral movement if there is an obstacle
3 components of phloem vessels
- sieve tube element -> living but nearly empty
- sieve plate -> perforated end cell walls
- companion cell -> respire excrete etc. on elements behalf, many mitochondria
How does sucrose enter the sieve elements?
- H+ actively transported to cell wall of comp. cell
- H+ the diffuse down conc. gradient back into comp. cells
- co-transport of sucrose with H+ ions
- sucrose diffuses into sieve tube elements through plasmodesmata
How do organic substances move by mass flow?
At source: sucrose in = water in = high pressure
At sink: sucrose out = water out = low pressure
Hydrostatic pressure gradient set up from source to sink which substances move down
Name 3 methods for investigating transport in plants
Ringing experiment
Tracer experiment
Aphids (probiscus)
Order of cardiac cycle
diastole (relaxation) atrial systole (contraction) ventricular systole (contraction
