7 - Mass Transport Flashcards
structure of haemoglobin molecules
protein with a quaternary struture evolved to make it effective at carrying oxygen
consists of 4 polypeptide chains linked to form an almost spherical molecule
each polypeptide chain is associated with a haem group
haem group
contains an Fe (II) ion each Fe (II) ion can combine with an oxygen molecule
process by which haemoglobin binds with oxygen molecules
associating / loading
process by which haemoglobin releases oxygen molecules
dissociating / unloading
effect of carbon dioxide on haemoglobin
carbon dioxide causes haemoglobin to change shape, reducing haemoglobin affinity for oxygen
myoglobin
a quaternary protein with just one haem group
has high affinity for oxygen even at low partial pressures
found in muscle cells
double circulatory system in humans
one sytem to lungs, one system to the body
maintains pressure
hepatic arteries/veins
to/from liver
renal arteries/veins
to/from kidneys
arteries
away from the heart
high pressure
thick outer wall of collagen and connective tissue
smooth muscle and elastic tissue can stretch and recoil
veins
thin outer wall of collagen and connective tissue
smooth inner layer of muscle and elastic tissue
large lumen
semi-lunar pocket valves to prevent backflow
aorta
carries oxygenated blood to the body
vena cava
carries deoxygenated blood from the body to the heart
pulmonary artery
carries deoxygenated blood to the lungs
pulmonary vein
carries oxygenated blood from the lungs to the heart
cardiac cycle
diastole, atrial systole, ventricular systole
diastole
ventricles and atria relax
semilunar valves closed
atrioventricular valves open
atria fill with blood from veins
atria systole
atria contract
blood forced into ventricles
semilunar valves closed
atrioventricular valves open
ventricular systole
atria relax and ventricles contract
blood forced into arteries
atrioventricular valves closed
semilunar valves open
formation of tissue fluid
- high hydrostatic pressure in capillaries at arterial end forces water and small molecules out
- this is tissue fluid and moves into spaces between the cells
- it is similar to blood but doesn’t contain plasma proteins
- at arterial end, blood pressure > osmotic pressure
- at venous end, greater osmotic pressure due to plasma proteins draws tissue fluid back in
- some fluid is drained into lymphatic vessels
xylem
tissue that transports water in plants
consist of dead cells which produce lignin
lignin
provides mechanical strength and waterproofing for the xylem tissue
transpiration
water evaporates from mesophyll cells in the leaf
as water evaporates, more molecules are drawn up behind it due to cohesion
a column of water is therefore pulled up the xylem due to transpiration
this creates negative pressure in the xylem - COHESION TENSION THEORY
translocation
transport of soluble organic substnaces and some mineral ions in the phloem
source
any area where sucrose is produced (usually leaves)
sink
where sucrose is delivered to and used
mass flow hypothesis
sucrose moves into companion cells by facilitated diffusion
sucrose co-transported with protons into sieve tubes from companion cells
water potential therefore lowered in sieve tubes
water enters tubes from xylem by osmosis
high pressure at source and low pressure at sink creates pressure gradient
causes organic substances to translocate
