Mass Transport Flashcards
What is the explanation for the shape of the oxygen dissociation curve?
- due to the shape of the haemoglobin, it is difficult for the first molecule to bind, hence the shallow curve at the bottom left
- once first oxygen binds, the Hb changes shape, making it easier for the next two oxygen molecules to bind, hence the steep middle section of the curve
- due to shortage of available binding sites, it is less likely that the fourth molecule will bind, hence the plateau
What are the stages of blood flowing through the heart?
1) Right atrium muscles relax and blood fills the atrium from the vena cava
2) Right atrium muscles contract, pushing the right atrioventricular valve down and forcing blood into the relaxed right ventricle
3) Right ventricle muscles contract, closing the right atrioventricular valve, opening the semi-lunar valve and forcing the blood into the pulmonary artery
4) Blood comes in through the pulmonary vein into the relaxed left atrium
5) Left atrium muscles contract, pushing the atrioventricular valve down and forcing blood into the left ventricle
6) Left ventricle muscles contract, closing the left atrioventricular valve, opening the semi-lunar valve and forcing blood into the aortaW
What is the definition of affinity?
The degree to which one substance combines with another
What are the steps in the transport of oxygen?
1) At gas exchange surface, there is high levels of oxygen, raising the pH
2) High pH changes shape of Hb molecule, increasing it’s affinity for oxygen
3) High affinity means oxygen is not released while transporting
4) Acidic solution from dissolved CO2 changes shape of Hb, reducing it’s affinity for oxygen
5) Low affinity means that the oxygen will readily release the oxygen to the tissues that require it
Give two examples of haemoglobin adapted for low oxygen levels and how
Foetal and llama haemoglobin have slightly altered quaternary structures to increase the molecules affinity for oxygen, compensating for the low environmental levels of oxygen
What are the feature of arterioles in relation to arteries?
- similar to arteries, but with more smooth muscle and less elastin as they do not need to withstand the same pressure levels
- smaller than arteries, with a larger lumen
Why are there greater pressure changes in arteries closer to the heart?
They have more elastic fibres, allowing them to expand and contract more to cope with the increased blood flow, emphasising the changes in pressure
What are the features of veins?
- carry blood towards heart at a low pressure
- minimal muscle and elastin, allowing it to be compressed by skeletal muscles to force the blood upwards
- have valves, which squeeze shut to prevent back flow of blood
What is the definition of cardiac output?
Volume of blood pumped by one ventricle of the heart in one minute
What is the product of oxygen and haemoglobin?
Oxyhaemoglobin
What is the structure of haemoglobin?
- made of four globin subunits, each made of a polypeptide chain and a haem group
- globin subunits held together by disulphide bonds
- each haem unit can hold one oxygen molecule, so each haemoglobin molecule can carry 4 oxygen molecules
What are the features of the capillaries?
- forms an extensive network between arterioles and venules
- very narrow lumen, sometimes the width of a singular red blood cell
- very thin walls, decreasing diffusion distance
- highly branched
What occurs in atrial systole?
- ventricles relax and atria contract
- increases atrial pressure
- atrioventricular valves open
- blood flows out of the atria into the ventricles
How are red blood cells adapted for their role?
- small and flexible so they can fit through capillaries
- biconcave shape, increasing surface area to absorb oxygen
- thin membrane so gas can easily diffuse
- contain haemoglobin, which binds to oxygen
What type of circulatory system do mammals have?
Closed, double circulatory system, meaning that blood passes through the heart twice for every complete circuit of the body
What is vasodilation?
Smooth muscle relaxes, dilating the vessel and increasing blood flow
What is the role of the ventricles?
Pump blood to arteries to transport blood away from the heart
What is the role of the atria?
Collect blood from the body and pump it into the ventricles
What occurs in ventricular systole?
- ventricles contract and atria relax
- increases ventricular pressure
- semi-lunar valves open and atrioventricular valves close
- blood flows into the arteries
What is vasoconstriction?
Smooth muscle contracts, constricting the blood vessel and decreasing blood flow
What are the stages of the cardiac cycle? (no description)
1) atrial systole
2) ventricular systole
3) diastole
Why does haemoglobin’s affinity for oxygen decrease in the presence of carbon dioxide?
1) Dissolved CO2 is acidic, so the pH of the solution lowers
2) Low pH changes the quaternary structure of the Hb by denaturing some of the peptide bonds
3) This change reduces the affinity for oxygen, meaning that the haemoglobin more readily dissociates from the oxygen
What occurs in diastole?
- ventricles and atria relax
- semi-lunar valves close and atrioventricular valves open
- blood flows passively into the atria and will trickle down into the ventricles
What is the oxygen dissociation curve?
Curve that shows the rate at which oxygen associates and dissociates with haemoglobin at different partial pressures of oxygen
