Transport of o2 and co2 in the blood (8) Flashcards
what are haemoglobin and myoglobin
respiratory pigments
what is haemoglobin. What is its structure. where is it found
found in erythrocytes. its a large globular protein in RBCs, has quaternary structure (made of more than 1 polypeptide chain, 2 alpha, 2 beta) each polypeptide chain attached to a haem group (prosthetic group). cos of the prosthetic group haemoglobin is a conjugated protein. the haem groups have an affinity for oxygen, a haemoglobin can carry 4 o2 molecules
What is a fully saturated haemoglobin
the haemoglobin is carrying the max amount of o2 molecules.
what is loading/association
adding o2. happens in the lungs, o2 moves down conc gradient of the alveolar air space and into the erythrocytes
the hb has an affinity for o2 and so become associated - no bond between them
what is unloading/dissociation
loss of oxygen. happens in respiring tissues, o2 moves down conc gradient from the erythrocytes into the tissues where o2 is used in ar and its concentration remains low.
as the hb releases the o2 it dissociates.
what is myoglobin (beyond syllabus, helps w applied Qu’s)
a protein, an o2 store in muscle cells. 1 haem group. forms oxymyoglobin when it picks up o2 from oxyhaemoglobin, releases o2 when levels fall (in muscles after exercise).
-has higher affinity for o2 than hb, so will pick up o2 when oxyhaemoglobin is releasing it
summary - transport of o2
-loads onto hb in lungs - oxyhaemoglobin
-travels in blood as oxyhaemoglobin to muscles
-dissociates from oxyhb to associate w myoglobin - oxymyoglobin
-stored in muscles as oxymyoglobin
-is released when the muscles are working hard to allow aerobic resp to continue for longer before switching to anaerobic resp.
What is the composition of the air
78.5%nitrogen 20%o2 0.04%co2 1%argon
what happens to density of air the further above sea level you are
the density decreases (as the number of molecules above you decreases as you go higher up)
what does partial pressure of gases measure
the concentration of each particular gas present
what is po2 (partial pressure of o2)
the pressure the o2 exerts in a gas mixture. units kPa. The concentration of oxygen.
what is co operative binding
it is difficult for the the o2 to bind to the hb at 1st, but then the haemoglobin shape distorts - allosteric effect. this allows more o2 molecules to bind easier
at low po2 (concentration of o2) does the HB offload oxygen easier or not
easier
what does co operative binding ensure
that haemoglobin is very good at delivering large amounts of o2 to tissues if required
At low oxygen concentration what is haemoglobin able to do
the haemoglobin offloads its oxygen easier (the HB dissociate w the o2, so it has 3, 2,2 or no o2 associated w it)
what does the number of o2 molecules offloaded depend on
it depends on the rate of aerobic respiration, the rate of o2 consumption, and the diffusion gradient for o2.
what causes saturated haemoglobin to release most of its o2
a low affinity for o2 in the low po2 conditions of respiring muscles.
What does the sigmoid (s) curve shape indicate
Cooperative binding between haemoglobin and oxygen
Why does myoglobin have a greater affinity for oxygen than haemoglobin
The haem group has a higher affinity for oxygen than the haem group of haemoglobin
On an oxygen dissociation curve graph, why does the myoglobin curve lie left of the haemoglobin curve, and why is it a steeper curve
Myoglobin will pick up and store oxygen at much lower concentrations than haemoglobin does.Myoglobin holds onto its oxygen for longer. Myoglobin has a greater affinity for oxygen
Oxymyoglobin is an oxygen store, When does oxymyoglobin release its oxygen
When the muscles are working hard, it may be using o2 for respiration faster than oxyhaemoglobin can supply it. The o2 concentration will get lower and lower until the oxymyoglobin then releases its o2
Why does oxymyoglobin only release o2 when levels of it are low
Oxymyoglobin holds onto its o2 so it can provide extra o2 to the muscle and allow it to keep respiring aerobically for abit longerbefore it ahs to switch to anaerobic respiration.
once oxymyoglobin has released its store of o2 when does it gain back its o2
when the oxygen debt has been repaid, the myoglobin is converted back to oxymyoglobin by taking o2 from oxyhaemoglobin.
how does myoglobin become oxymyoglobin
myoglobin takes o2 from oxyhaemoglobin, its able to do this due to its greater affinity for o2 than haemoglobin
what is the structure of fetal haemoglobin
its made up of 2 beta chains and 2 gamma chains. (while adult haemoglobin is made up of 2 alpha and 2 beta chains)
why does fetal haemoglobin have a higher affinity for o2 than adult haemoglobin
the developing fetus needs to be able to take o2 from the maternal blood at the placenta. this woiud not be as efficient if the fetal and maternal haemoglobin had the same affinity for oxygen. the blood offloads o2 easier to blood of a higher o2 affinity.
which has a higher affinity for oxygen: myoglobin or fetal haemoglobin
myoglobin trumps all
does blood offload o2 easier to blood of a higher affinity
yes
what affects the ability of haemoglobin binding with o2
oxygen concentration and co2 concentration
how much co2 dissolves straight into the plasma
5%
how is the compound carbaminohaemoglobin formed
co2 combines with the amino groups in the polypetide chains of haemoglobin.
how much co2 combines w amino groups to make carbaminohaemoglobin
10-20%
what does the majority 75-85% of the co2 do
it diffuses into te RBCs for conversion into hydrogencarbonate
what enzyme do RBCs contain
carbonic anhydrase
what does carbonic anhydrase do with the co2 in the blood
it catalyses a reaction in which co2 forms a weak acid called carbonic acid
what does the carbonic acid then do
some of the acid dissociates producing hydrogen ions and hydrogencrabonate ions
what do the hydrogencarbonate ions then do
they diffuse out out of the RBC and into the plasma (this is how majority of co2 is carried in the blood)
what do the hydrogen ions then do
they combine with haemoglobin molcules inside the RBCs, forming a compound called haemoglobinic acid.
if a haemoglobin molecule is binded to an co2 molecule what can it then not do
it cannot then bind to a o2 molecule, as the hydrogen ions make it drop its o2
hydrogen iions + haemoglobin=?
haemoglobinic acid
by accepting hydrogen ions the haeomglobin acts as a buffer, what does this prevent
it prevents a drop in pH and the conditions becoming too acidic
what is the chloride shift
chloride ions moving into the RBCs
what is the point of the chloride shift
it happens to maintain charge in RBC
what happens to oxyhaemoglobin when its underthe influence of hydrogen ions
the oxyhaemoglobin dissociates, loses all o2
what is the Bohr effect
the percentage saturation of haemoglobin is lower when co2 concentration is high
co2 + haemoglobin = ?
carbaminohaemoglobin
