Module 3.1.2 - Transport in animals Flashcards
What are the specialised features of an erythrocyte?
Flattened bi-concave shape (large SA to volume ratio).
Large amount of haemoglobin for transporting oxygen.
No nuleus or organelles so more space for haemoglobin for oxygen.
Diameter 6-8micrometers, larger than capillary diameter. Slows blood flow to enable diffusion of oxygen.
What is the size of an erythrocyte and how does this help it’s function?
Small diameter of 7 micrometers, normal cell is 40 micrometers diameter.
Therefore haemoglobin is very close to the plasma membrane - as a result oxygen is loaded and unloaded into and out of a cell.
Capillaries are 8 micrometers wide, only one erythrocyte can go through at a time.
What is haemoglobin?
A protein making up 95% of the dry mass of a RBC. It is the means of oxygen transport around a body.
What is haemoglobin’s structure?
Haemoglobin is made from four haemoglobin groups each bound to a haem group.
Each haem group can combine with one oxygen molecule, so one haemoglobin molecule can combine with four oxygen molecules. This forms oxyhaemoglobin.
What ion does haemoglobin contain at the centre?
The haem group contains a single iron ion in the form Fe 2+.
True or false. Haemoglobin has a high affinity for oxygen?
True.
How is the saturation of haemoglobin measured?
As a percentage.
What is positive cooperativity?
As soon as one oxygen binds to a haem group, it changes the shape of the molecule and makes it easier for more oxygen to bind.
Because the oxygen is binded to the haemoglobin the free oxygen concentration gradient in the erythrocytes remains low, so a steep concentration gradient is maintained until all of the haemoglobin is saturated with oxygen.
When does oxygen bind to and leave haemoglobin?
Oxygen binds to haemoglobin when oxygen is at a high concentration and dissociates when oxygen is at a low concentration.
How is oxygen concentration measured?
The concentration of gas in a mixture of gases can be measured as the partial pressure. This is the amount of pressure the gas exerts relative to the total pressure exerted by all the gases in the mixture.
Measured with kilopascals (kPa) and is written as P(O2), P(O2) etc
What is the oxygen dissociation curve?
A graph that shows the saturation of haemoglobin at various partial pressures of oxygen.
LOOK AT POWERPOINT OR BOOKLET FOR OXYGEN DISSOCIATION CURVE GRAPHS.
What is the trend with oxygen dissociation?
Generally, the greater the concentration of oxygen, the greater the affinity.
In the lungs the partial pressure is high so haemogloin has a 90-95% saturation of haemoglobin.
At respiring tissues, partial pressure is low, so haemoglobin loses oxygen to 20-25% concentration.
How is fetal haemoglobin different to adult haemoglobin?
Fetal haemoglobin has a higher affinity for oxygen.
This is because fetal haemoglobin has to associate with oxygen in an environment where partial pressure of oxygen is low enough to make adult haemoglobin release oxygen.
Helps maximise uptake of oxygen from the mother’s bloodstream.
What are the 3 ways that carbon dioxide are transported?
About 5% is carrier dissolved in the plasma.
10-20% is combined with the amino groups of haemoglobin to form carbaminohaemoglobin.
75-80% is converted to hydrogen carbonate ions in the cytoplasm of red blood cells which then diffuses into the plasma.
