Mass Transport Flashcards
Mass transport system
movement of a huge number of substances in the same direction at the same time
Double circulatory system
confined to vessels and blood passes through the heart tissue twice for each complete circuit- from heart to lungs and heart to body
Haemoglobin structure
quaternary protein made up of 4 polypeptide chains each with a haem group containing an iron ion
each iron ion can bind with an oxygen molecule so hb can bind with 4 o2 molecules- oxyhaemoglobin
Haemoglobin function
transports o2 around the body by associating with o2 in the lungs and dissociating at the tissues
it has a chemical attraction/ affinity for o2
Dissociation curve
s shaped curve which shows the binding of o2 to hb
1st o2 is hard to bind so curve is not steep
2,3rd o2 easily taken up by hb as the quaternary structure is affected when the first o2 binds
-allows o2 to be taken up quickly in lungs
4th is hard to bind as it has to find empty iron ion so curve is flatter
Dissociation curve shift
curve shifts to right- lower affinity for o2 so it will unload more readily and load at higher po2- smaller animals or those who respire more, have greater SA:V so lose heat (maintain temp)
curve shift to left- higher affinity for o2 so it doesn’t unload as easily, o2 binds at low po2- animals who live in environments with little o2 (high altitude) + lugworms
Bohr shift
during exercise co2 levels rise (carbonic acid) which lowers the ph of blood making it more acidic which changes the shape of hb - has a lower affinity and unloads o2 more readily at respiring tissues
curve shifts to the right known as bohr effect
Cardiac cycle
sequence of events that occur in one heart beat
atrial systole- ventricular systole- diastole
AS- atria are full of blood and contract, higher pressure in atria than ventricles, AV valves open and blood flows to ventricles
VS- ventricles are full of blood and contract, higher pressure in ventricles so AV valves shut and SL valves open and blood flows to arteries
D- atria and ventricles relax (low pressure), blood trickles into atria, blood trickles into atria from vena cava and pul vein, pressure higher in atria, AV valves open, pressure higher in arteries, SL valves shut
Cardiac output
stroke volume x heart rate
stroke volume= highest volume-lowest volume
calculating bpm- find out time of one heart beat
look when volume of blood repeats itself
work out how many beats in one minute- 60/time of one heart beat
higher pressure in ventricles as more muscle
Blood vessels
arteries, arterioles and veins have layered structure surrounding lumen of endothelium, elastic layer (stretch to receive blood at high pressure, recoil when blood pressure decreases), muscle layer (controls blood flow by contracting and relaxing vasoconstriction + vasodilation ),
tough fibrous layer to resist pressure
blood in veins keeps moving by contraction of skeletal muscles, valves preventing back flow, wide lumen
capillaries- surround cells and tissue fluid and assist with exchange of substances
Tissue fluid
surrounds the cells in the body and provides a medium that allows o2 and glucose etc to travel out of capillaries
formed:
high hydrostatic pressure at arteriole end
forces water (+glucose) out through capillary walls
large proteins and RBC remain in capillary
lowers water potential
water moves back in at venous end by osmosis
from high wp outside to low wp inside
low pressure at venous end due to loss of fluid
lymph system collects excess tissue fluid which links with vena cava and returns tf to circulatory system
Capillaries
structures that aid their function;
walls consist of endothelium so short diffusion path
narrow lumen so rbc up tight against capillary wall meaning they are closer to body cells
highly branched increasing surface area and rate of diffusion
Cardiovascular disease
weakens the heart, reduces cardiac output and increases the risk of heart attack
risk factors- excess saturated fat leads to build up of atheroma causing atherosclerosis
smoking- carbon monoxide binds with hb
high cholesterol levels
genetics, age, sex
Transpiration
evaporation of water from leaves through open stomata
transpiration pull/stream moves water up from root to leaf
-water molecules evaporate from mesophyll cells then move through air spaces in the leaf and diffuse out of stomata
-lowers wp of mesophyll cells so water moves from high to low wp from neighbouring cells into mesophyll cells by osmosis
-lowering wp is repeated back to xylem
-the wp gradient across the leaf to the atmosphere pulls water up from the xylem- transpiration pull
(cohesion tension theory)
Xylem
carry water
xylem vessels are dead cells with no end walls
form continuous tubes from roots to leaves
lined with lignin to prevent cells collapsing under tension
connected through pits which allow lateral movement of water if pathway is blocked
have no organelles to allow water travel without being blocked
Cohesion- tension theory
water evaporates from leaves
reduces wp in cell and water is drawn out of xylem
transpiration pull/ suction creates negative pressure called tension
water moves up the xylem from roots to leaves
water moves as a continuous column as water is dipolar and has cohesive properties
evidence- diameter of a tree in the day is smaller than at night due to more tension in the xylem as more stomata are open, tension pushes inwards
Potometer
can be used to investigate rates of water uptake of a shoot under different conditions
must be prepared under water to prevent air bubbles
cut shoots under water to prevent air bubbles
bubble is created by tapping the end of the tube
rate of water uptake=distance travelled by bubble/time
volume “ /min= πr2 x distance travelled by bubble/time
volume of water taken up isnt equal to water lost in transpiration as respiration occurs which produces water and photosynthesis uses water
Factors affecting transpiration
light intensity- whether stomata are open or shut
temp- higher temp increases evaporation rate
humidity- reduces wp gradient between leaf and air
Controlling water loss
guard cells control water loss by changing shape to increase or decrease the size of the stomata
day- guard cells turgid/swollen so stomata are open
night- guard cells shrink so stomata are closed
rolled leaf- water vapour evaporating from stomata gets trapped in rolled leaf reducing wp gradient
hair- traps water as air is more humid between hairs which reduces wp gradient
sunken stomata- stomata are in pits which accumulate water vapour (humid) which reduces wp gradient
Translocation
the movement of organic substances around the plant, in sieve tubes, from source to sink
Phloem
sieve tubes are made up of living, elongated cells
cells consist of sieve element and companion cell
end of sieve elements have holes and form sieve plates
sieve elements lose organelles so that nutrients within sap can flow more easily
companion cells provide metabolic support
Mass flow hypothesis
sucrose is actively transported from source to companion cell then into sieve cell by facilitated diffusion
this lowers wp in sieve cells so water moves in from high wp in xylem to low wp in sieve cells
this increases the volume in sieve cells which increases hydrostatic pressure
sucrose moves down a hydrostatic pressure gradient
sucrose is unloaded at respiring cells and used in resp.
respiratory inhibitors- inhibit translocation as stop ATP from being produced so sucrose cannot be actively transported into companion cell
MFH- evidence
for- if phloem is cut open, sap seeks out due to hydrostatic pressure
sucrose conc is higher in source than sink
low light reduces translocation due to reduced sucrose production from photosynthesis
lack of oxygen reduces translocation as ATP produced is reduced from respiration
ringing + tracing exp
against- role of sieve plates is unknown and it looks like they could hinder movement of substances
different types of solutes move at different speeds
movement could be due to gravity
Investigating MFH
tracing- grow a plant in presence of radioactive C so that it is incorporated into its sugar and they can be tagged
results shown in autoradiography where the stem is placed on an x ray film, it will blacken where exposed to C in the sugars- blackens on phloem
ringing-remove the outer part of their stems, including the phloem, supply the leaf with 14CO2, take cross section samples of the stem above and below the ring and perform autoradiography.
unringed shoot is radioactive in phloem tissue
throughout the plant.
ringed shoot is radioactive before the ring but not
after. Proving translocation occurs in the phloem.
tissue fluid + salt
high salt concentration can lead to build up of tissue fluid
creates high blood pressure so more fluid is pushed out of the capillary
more tissue fluid outside
has low wp (lots of salt) so no wp gradient for water to enter back by osmosis
less water returns by osmosis
SA:V and metabolic rate
smaller animal will have greater SA:V ratio
they will lose heat faster
so they need a faster rate of metabolism/ respiration which releases heat
haemoglobin binding
first binding of o2 takes a long time
once it binds, changes tertiary/quaternary structure of hb which uncovers another binding site/ Fe ion for o2 to bind to
