haemoglobin Flashcards
what is haemoglobin
protein
4 polypeptide chains (2 alpha 2 beta)
each polypeptide chain is folded round a haem group
each haem group can combine with an oxygen
4 haem groups= max of 4 oxygen combined to make oxyhaemoglobin which carried oxygen around the body
what’s the difference between the use of haemoglobin in different animals
some animals haemoglobin acts as an oxygen carrier loaded with oxygen in lungs/ gills and unloads in tissues
in other animals (eg larvae) haemoglobin acts as a store of oxygen- becoming loaded with oxygen from the environment and unloading when oxygen levels fall
what is the partial pressure of oxygen
measures the amount of oxygen present in the air, blood or tissues
what the saturation of haemoglobin with oxygen
haemoglobin that has 4 oxygens bound to every haemoglobin molecule is 100% saturated
what happens as the partial pressure of oxygen increases
haemoglobin gets more saturated
shown in a dissociation curve
which is a sigmoidal shape
explain why dissociation curves are a sigmoidal shape
- first oxygen molecule binds to the haemoglobin molecule has trouble doing so as only 1 haem group is exposed and available therefore graph rises slowly to start with
-when it does bind the first oxygen molecule changes the tertiary structure and the quaternary structure of the haemoglobin molecules. This exposes more haem groups so it easier to bind so dissociation curve rises steeply
-once some of the haemoglobin molecules already have 4 oxygen molecules bound they cannot take any more oxygen. Therefore the graph starts to level off
use the dissociation curve in an example in humans
in the lungs, the partial pressure of oxygen in the alveoli air spaces is high
therefore oxygen diffuses into the blood and haemoglobin becomes highly saturated
In the tissues the partial pressure of oxygen is low as tissue cells sue of oxygen for respiration. Therefore oxygen dissociates from haemoglobin and diffuses from the blood into tissues.
what makes dissociation curves different
different properties of haemoglobin
what makes the dissociation curve move to the left
greater tendency to bind to oxygen
what makes the dissociation curve move to the right
grater tendency to release oxygen
explain chironomids haemoglobin
-live at the bottom of ponds
-curve is to the left of humans
-shows that ahemogobin has a high affinity for oxygen and tends to be highly saturated at medium and low partial pressures
-advantage= haemoglobin becomes saturated with oxygen at normal partial pressures. If the partial pressures fall low, oxygen dissociated from oxyhaemoglobin and becomes available for respiration
explain swallows haemoglobin
-fly for long periods of time so oxygen is needed at a rapid rate
-curve to the right of human
-shows the haemoglobin has a low affinity for oxygen and tends to dissociate easily at a wide range of partial pressures especially high
-advantages= oxyhaemoglobin formed tends to dissociate rapidly in tissue so oxygen is available for respiration
what is the bohr effect
-carbon dioxide affects PH in a solution
-the higher the concentration on carbon dioxide the more acidic
-the affect of acidity on heaemoglobin= changes its tertiary structure and lowers its affinity for oxygen
explain the bohr effect in lungs
- the concentration of carbon dioxide is lower, so the haemoglobins affinity for oxygen increases
-dissociation curve shifts to the left so haemoglobin becomes saturated at a range of partial pressures
whn the partial pressure is high that means theres more frequent ventilation
explain the bohr effect on blood transported to the tissues
-concentration of carbon dioxide is higher (due to respiration)
-lowers the pH and the affinity for oxygen
-dissociation curve moves to the right so haemoglobin releases its oxygen
-partial pressure in tissues is low because of respiration
-so oxyhaemoglobin tends to become unsaturated which releases its oxygen so it diffuses into the tissue and is used for respiration
