Transport of gases C3 Flashcards
what is blood?
an aqueous medium which allows for gas exchange and the delivery of important molecules such as glucose and oxygen
what is plasma?
straw-coloured fluid in blood
it comprises blood cells
is blood a tissue
yes
what does plasma contain?
90% water with a range of dissolved materials which are:
proteins
glucose
clotting factors like fibrinogen
mineral ions
hormones
antibodies
dissolved CO2
what else does plasma do?
transport dissolved materials
distributes heat around body
what are the three types of blood cells?
leucocytes - white blood cells for immunity
thrombocytes - platelets for blood clotting
erythrocytes - red blood cells for oxygen transport
what two groups can leucocytes be divided into?
granulocytes
agranulocytes
what are granulocytes?
they have granular cytoplasm and lobed nuclei meaning the cell has more space and is more flexible
their function is to engulf pathogens by phagocytosis
what are agranulocytes?
they produce antibodies and antitoxins, have a clear cytoplasm and spherical nucleus
the antibodies/antitoxins are made of protein so these cells have RER and SER and Golgi body
what are erythrocytes filled with?
the pigment haemoglobin (Hb)
what three features do erythrocytes have to allow them to efficiently transport oxygen?
biconcave shape allows a greater surface area for diffusion
no nucleus and few organelles so there is more space to fit haemoglobin
flexible elastic membrane to squeeze through narrow capillaries
what is haemoglobin?
a complex globular protein with a quaternary structure consisting of four folded polypeptide chains
at the centre of each polypeptide is a haem group which contains iron (Fe2+)
each haem group is a binding site for one oxygen molecule
how is oxyhaemoglobin formed?
one molecule of haemoglobin can bind to four molecules of oxygen
what intermolecular bonds can be found in Hb?
hydrogen bonds
disulphide bridges
ionic bonds
the reaction between haemoglobin and oxygen is reversible and can be represented in the form of an equation. what is this equation?
Hb + 4O2 (double-headed arrows) Hb.O8
define affinity
the degree to which one molecule (haemoglobin) is chemically attracted to another molecule (oxygen)
define saturation
the percentage of oxygen bound to haemoglobin
define association/loading
the uptake of oxygen by haemoglobin to form oxyhaemoglobin in the lungs
define dissociation/unloading
the release of oxygen at the respiring tissues to form haemoglobin
how is oxygen transported?
oxygen diffuses into red blood cells and associates with haemoglobin to form oxyhaemoglobin
oxygen concentration is measured by partial pressure (kPa)
when the partial pressure of oxygen is high eg in the lungs, haemoglobin has a high affinity for oxygen and so oxygen associates with haemoglobin to form oxyhaemoglobin
when the partial pressure of oxygen is low eg in the respiring tissues, haemoglobin has a low affinity for oxygen and so oxygen dissociates from oxyhaemoglobin, forming haemoglobin
list 4 ways in which the shape of the haemoglobin dissociation line differs from the theoretical line
haemoglobin line is s-shaped
actual line rises much more steeply between 2kPa and 7kPa/steeper in the middle
theoretical line shows no flattening on top
haemoglobin shows higher saturation throughout
what is cooperative binding?
describes the ease with which a haemoglobin molecule binds a second and a third oxygen molecules, compared with the first and fourth
describe cooperative binding with haemoglobin
as haemoglobin is a protein, any molecule that associates with it will cause a slight change in shape
once the first molecule of o2 is associated with haemoglobin, it causes a change in shape that makes the second and third binding sites more available, increasing haemoglobin affinity for oxygen
the 2nd and 3rd o2 molecules associate more easily than the first
it is then more difficult for an oxygen molecule to associate with the last binding site
therefore the binding of o2 to Hb is not directly proportional to oxygen concentration
as a result the line of the o2 dissociation curve is not straight but instead a sigmoid curve (s-shaped)
describe the sigmoid graph
start - at very low ppo2 it is difficult for haemoglobin to load oxygen
in respiring tissues, the ppo2 is low because oxygen is being used up in aerobic respiration
the oxygen then unloads from oxyhaemoglobin (dissociates)
oxygen affinity decreases as ppo2 decreases
this means that it is readily released to meet respiratory demands
a very small reduction in the ppo2 leads to o2 unloading from oxyhaemoglobin rapidly
haemoglobin’s affinity for oxygen is high at high partial pressures of oxygen
haemoglobin loads oxygen in the lungs, where the ppo2 is high
the haemoglobin becomes saturated with o2 and forms oxyhaemoglobin
o2 is transported in this form to respiring tissues such as muscles
how does a pulse oximeter estimate the o2 saturation in your blood?
by sending infrared light into capillaries in your finger
then measures how much light reflected off the gases
the o2 saturation of Hb measured in a healthy person is 98/99%. Why is it not 100%
some o2 used by respiring cells in the alveoli
the rate of blood flow through the pulmonary capillaries is still too fast for all o2 to diffuse into the blood
what does foetal haemoglobin’s o2 dissociation curve look like and what does it mean?
curve shifted to the left of the adult curve
means it has a higher affinity for o2 therefore can load o2 from the mother’s blood at all partial pressures of o2
why doesn’t a baby retain its foetal haemoglobin once it is born?
foetal haemoglobin’s high affinity for o2 means that it doesn’t efficiently give it up at respiring tissues
adult haemoglobin needs a lower affinity for o2 than foetal so that o2 can pass from mothers to their foetuses
what happens to ppo2 at high altitudes?
drops
with an increase in altitude, there is a drop in atmospheric pressure and therefore a reduction in the ppo2
since llamas live in high altitudes, how do they compensate for the low ppo2? and what happens to the o2 dissociation curve?
a llama’s haemoglobin has a higher affinity for o2 and therefore picks up o2 more readily at the lungs
curve is shifted to the left