3.3 organism exchange- haemoglobin Flashcards
what is haemoglobin
Found in blood
A group of chemically similar molecules found in red blood cells that transports oxygen
Large protein with a quaternary structure
Is a globular protein- oxygen-carrying pigment in red blood cells ( 2 alpha and 2 beta)
Each molecule of haemoglobin can carry four oxygen molecules
oxyhaemoglobin
In the lungs, oxygen joins to haemoglobin to form oxyhaemoglobin in a reversible reaction
Near body cells, oxygen leaves oxyhaemoglobin
When oxygen joins, its called association/ loading
When oxygen leaves, its called dissociation/ unloading
Haemoglobin + oxygen ⇌ oxyhaemoglobin
Hb + 4O2 ⇌ HbO3
loading oxygen
Low oxygen concentration
Polypeptide chains are squished together
Hard for Hb to bind to the 1st molecule
1st oxygen molecule attaches, shape changes which makes it easier for the remaining oxygens to load
Haemoglobin is soluble in water, but oxygen isn’t
Oxygen can be carried more efficiently around the body when bound
As each oxygen molecule binds to a haem group it changes tertiary and the quaternary structure of the protein
Uncovers another binding site haem group/Fe for oxygen to bind to, increasing the affinity for oxygen
Iron II ions in haem group allow oxygen to reversibly bind
oxygen dissociation curve
Shows how saturated the haemoglobin is with oxygen at any given partial pressure
Where PO2 is high, haemoglobin has a high affinity for oxygen, so it has a high saturation of oxygen.
Where PO2 is low, haemoglobin has a low affinity for oxygen so it has a low saturation of oxygen
It is s-shaped due to the saturation of haemoglobin that cab affect the affinity of oxygen
When haemoglobin combines with the first oxygen, the shape alters in a way that makes it easier for others to bind
As it gets more saturated, it gets harder to join
Shallower curve - harder to join
If the curve shifts to the right, the affinity for oxygen decreases
If the curve shifts to the left, the affinity for oxygen increases
carbon dioxide concentration- Bohr effect
Partial pressure of CO2- PO2- Co2 concentration which affects oxygen unloading
Haemoglobin gives up oxygen more readily at a higher PCO2
When cells respire, they produce CO2, which increases PCO2.
Increases rate of CO2 unloading, so the oxygen dissociation curve shifts right.
Oxygen saturation with blood if lower for a lower PO2, meaning more oxygen is released
high activity levels
Organisms that are very active and have a high oxygen demand have haemoglobin with a lower affinity for oxygen than human because they need haemoglobin to easily unload oxygen so its available for use.
Dissociation curve is to the right
foetal haemoglobin
Has a higher affinity for oxygen than adults due to a difference in structure
This means foetal haemoglobin will load oxygen when adult haemoglobin is unloading from a placenta
affinity for oxygen
partial pressure of oxygen (PO2).
PO2- measure of oxygen concentration. The greater the concentration of dissolved in cells, the higher the partial pressure.
As PO2 increases, haemoglobins affinity for oxygen also increases. Oxygen loads into haemoglobin to form oxyhaemoglobin where there’s a higher PO2.
Oxyhaemoglobin unloads it oxygen where there’s a lower PO2.
size
Small mammals have a higher surface area to volume ratio than larger mammals so they lose heat quickly, so they have a high metabolic rate to keep them warm. This causes a high oxygen demand
Mammals that are smaller than humans have haemoglobin with a lower affinity for oxygen than humans and so need haemoglobin to easily unload oxygen to meet their oxygen demand
Dissociation curve is to the right
low oxygen environment
Organisms that live in environments with a low concentration of oxygen have haemoglobin with a higher affinity for oxygen than human haemoglobin as there’s much oxygen available so haemoglobin has must be good at loading any available
Dissociation curve is to the left of humans
alveoli in the lungs
High oxygen concentration
High PO2
High affinity for oxygen
Oxygen loads
saturation of haemoglobin with oxygen
When haemoglobin is holding the maximum amount of oxygen that it can bind
affinity for oxygen
The tendency a molecule has to bind to oxygen
In haemoglobin it varies depending on the conditions its in.
structure of haemoglobin
Flattened biconcave shape that ensures a large surface area to volume ratio
No nucleus or organelles to maximises space to allow more oxygen to be transported
Has 4 polypeptide chains each with a haem group that contains an iron.
The iron is what gives it it’s red colour
respiring tissues
Low oxygen concentration
Low PO2
Low affinity for oxygen
Oxygen unloads
