mass transport Flashcards
describe the structure of haemoglobin
globular protein made of 4 polypeptide chains
each associated with a haem group which contains an Fe+ ion
each Fe+ can combine with one molecule of O2
what is the role of haemoglobin in the transport of oxygen?
readily associate with O2 at gas exchange surfaces
readily dissociate from O2 at tissues
explain the shape of the oxygen dissociation curve (S shape)(3)
shape of haemoglobin makes it difficult for first oxygen bind bc they are closely packed
binding of first oxygen changes quaternary structure so shape changes, making it easier for other O2 molecules to bind
the last molecule has lower probability of binding as there are less empty sites
what is positive cooperativity?
when the binding of the first oxygen molecule increase the chance of the second binding
what is the Bohr effect?
the greater the concentration of carbon dioxide, the more readily the haemoglobin releases the oxygen molecule
what does it mean if the oxygen dissociation curve is further to the left?
there is a greater affinity for oxygen
what does it mean if the oxygen dissociation cure is further to the right?
there is a lower affinity for oxygen
Describe the advantage of the Bohr effect during intense exercise.(2)
more CO2 at cells so increased dissociation of oxygen for aerobic respiration.
why do large organisms require a transport system
small SA:V
more active
what type of circulatory system do mammals have?(2)
closed-blood is confined to blood vessels
double circulatory-passes through the heart twice
what are the 4 chambers of a heart?
right atrium
right ventricle
left atrium
left ventricle
what are the 4 vessels connected to the chambers of the heart?
aorta
vena cava
pulmonary artery
pulmonary vein
describe the flow of blood starting at the vena cava
unoxygenated blood enters right atrium -> right ventricle -> pulmonary artery -> lungs -> oxygenated blood enters left atrium -> left ventricle -> aorta -> body
what prevents backflow of blood into the atria and where are these located?
bicuspid valve (left)
tricuspid valve (right)
these are between the atria and the ventricles
what blood vessels supply the heart with oxygen?
coronary arteries
what happens when coronary arteries become blocked?
myocardial infarction(heart attack)
describe diastole(3)
relaxation of the heart
blood enters atria, increasing pressure
when pressure in atria greater than ventricles, atrioventricular valves open
pressure in ventricles is reduced as walls are relaxed, this means it is lower than in the arteries so semi lunar valves close
describe atrial systole(2)
contraction of the atrial walls along with the recoil of the relaxed ventricle walls
this forces remaining blood into ventricles
describe ventricular systole(3)
ventricle walls contract after a short delay
this increases pressure in ventricles so that it is higher than that in the atria, forcing atrioventricular valves shut.
this causes pressure to rise further so that it is higher than arteries, opening semi lunar valves
what valves are found in veins?
pocket valves
what is the equation for cardiac output?
cardiac output = heart rate x stroke volume
what are the 5 general layers of a blood vessel?
tough fibrous outer layer
muscle layer
elastic layer
thin inner lining
lumen
how is the structure of an artery related to its function?(4)
muscle layer is thicker than veins-can be constricted and dilated to control volume of blood
elastic layer is relatively thicker than veins-keep high blood pressure so that it can travel to extremities of the body
overall thickness of wall is great-resists vessel bursting under pressure
no valves-constant high pressure so blood tends not to backflow
how is the structure of a vein related to its function?(4)
muscle layer is thin-their constriction and dilation can not control the flow of blood to the tissues
elastic layer is thin-low pressure of blood will not cause them to burst
overall thickness is small- no need for a thick wall as pressure is too low to risk bursting
contains valves-ensures blood does not flow backwards
how is the structure of a capillary related to its function?
walls consist mostly of lining layer-makes them extremely thin so diffusion distance is small
numerous and highly branched-provides large surface area for exchange
narrow diameter- permeate tissues so no cell is far from a capillary
spaces between the lining-allows white blood cells to escape to deal with infections in tissues
describe how tissue fluid is formed(3)
- blood is pumped from arteries to arterioles then capillaries, creating high hydrostatic pressure at start of the capillary bed
- pressure forces tissue fluid out of capillary
- only small molecules are forced out, molecules like proteins and blood cells remain as they are too large to leave
describe how tissue fluid is returned to the circulatory system(5)
- loss of water reduces hydrostatic pressure in capillary
- pressure gradient is created at venous end, forcing some tissue fluid back in
- in addition, the proteins that remained creates a water potential gradient where it is higher inside
- this means water moves to the blood via osmosis
- remainder of tissue fluid is carried back via the lymphatic system
Describe the cohesion-tension theory of water transport in the xylem(6)
Water lost from leaf because of transpiration / evaporation of water
Lowers water potential of mesophyll
Water pulled up xylem creating tension
Water molecules stick together by hydrogen bonds which is cohesion
forming continuous water column
Adhesion of water molecules to walls of xylem
describe how sucrose is transferred into sieve elements(5)
- sucrose is produced from photosynthesis in chloroplasts in the leaf
- sucrose diffuses down conc gradient via facilitated diffusion to companion cells
3.H+ ions actively transported from companion cells into spaces within cell walls using ATP
- H+ ions diffuse down conc gradient into sieve tube elements via facilitated diffusion
5.sucrose is co transported along with H+
Describe the mass flow hypothesis for the mechanism of translocation in
plants(4)
In source sugars actively transported into sieve elements by companion cells
this lowers water potential of sieve cell and water enters by
osmosis from xylem
Increase in hydrostatic pressure causes mass movement of sucrose solution towards sink as pressure is lower at the sink
Sugars used / converted in root for storage
