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33 Cards in this Set
- Front
- Back
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Why do multicellular organisms need specialised mass transport systems? |
They have a small surface area to volume ration, so the diffusion is too slow and the distance is too great. |
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What does a mass transport system ensure? |
The efficient movement of molecules through the organism |
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What 2 factors determine whether there's a specialised transport medium and whether it's circulated by a pump? |
Surface area to volume ratio How active is the organism |
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What increases the need for a mass transport system? |
If the organism is active and has a small surface area to volume ratio |
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What is haemoglobin? |
A protein with a quarternary structure. It has 2 alpha chains and 2 beta chains. Each chain contains a haem group (Fe2+) |
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What does the Fe2+ do? |
The four haem groups have a high affinity for oxygen, so oxygen binds to them to form oxyhaemoglobin. This is reversible |
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What is it called when oxygen binds to a haem group? |
Loading |
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What is the reverse of this called? |
Unloading |
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Where is haemoglobin found? |
In erythrocytes |
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Define association/loading |
The process by which haemoglobin binds with oxygen. |
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Define dissociation/unloading |
The process by which haemoglobin releases oxygen |
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What does an oxyhaemoglobin dissociation curve show? |
How saturated the haemoglobin is with oxygen at different partial pressure of oxygen |
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What is part 1 of the curve? |
At low partial pressure, haemoglobin doesn't readily bind with oxygen as the haem groups are at the centre of the haemoglobin, making it difficult to bind.This means there's a low oxygen saturation. |
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What happens in part 2 of the curve? |
As oxygen partial pressure increases, the diffusion gradient increases, meaning that eventually, an oxygen molecule will bind t a haem group. This changes the shape of the haemoglobin, making it easier for more oxygen to bind. Gradient of the curve increases |
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What happens at part 3 of the curve? |
It's difficult for haemoglobin to become 100% saturated with oxygen even at high partial pressures.This is because, it's difficult for the last oxygen to diffuse and associate with the fourth haem group. |
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Where is stage 1 likely to occur? |
Near respiring tissue |
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Where is stage 3 likely to occur? |
The lungs |
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What represents the partial pressure of oxygen? |
pO2 |
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What is the chemical formula for the haemoglobin reaction? |
Hb + 4O2 <--> HbO8 |
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What are the conditions in the alveoli? |
High pO2 High affinity Oxygen loads |
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What are the conditions in respiring tissue?
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Low pO2 Low affinity Oxygen loads |
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What is the partial pressure of carbon dioxide? |
A measure of CO2 concentration in a cell. Represented by pCO2
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What happens at higher pCO2? |
Haemoglobin unloads oxygen more readily. This is caused when cells respire. |
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What does a higher pCO2 do to the curve and what is the called? |
It moves the curve right. The Bohr effect |
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What do different animals have? |
Chemically different haemoglobin with different oxygen-transporting capabilities. |
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What does the haemoglobin type depend on? |
Size of the organism, the environment and how active they are |
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What happens to the curve of haemoglobin for animals living in low oxygen environments? |
It shifts to the left, so haemoglobin has a higher affinity for oxygen as there isn't much available. |
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Give an example of an animal in a low oxygen environment |
Lugworms live in burrows under sand where there's low oxygen concentration. Their haemoglobin needs a higher affinity for oxygen than ours. |
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Which other haemoglobin matches the lugworms graph? |
Foetal haemoglobin |
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How do high activity levels effect the graph? |
These organisms have a higher oxygen demand, so haemoglobin has a lower affinity for oxygen than ours. Meaning they can easily unload oxygen. This shifts the graph to the right. |
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Give an example of an organism with high activity levels |
A hawk has a high respiratory rate and lives where there's plenty of oxygen. Its haemoglobin has a low affinity as it has to unload oxygen quickly to meet the high oxygen demand |
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What happens to the graph if organisms are smaller? |
The graph shifts right. This is because, the SA:vol ration is larger, so they lose heat faster. This means they have a high metabolic rate to keep warm and a high oxygen demand. This means they need to be able to quickly unload oxygen |
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Give an example of a small animal that fits this? |
A rat has a higher SA:vol ratio than us, so it needs to be able to unload oxygen faster to meet the greater demand. Haemoglobin has a low affinity for oxygen. |
