3.3.4.1 Mass transport in animals Flashcards
(35 cards)
How many oxygen molecules can each haemoglobin molecule carry?
Each haemoglobin molecule can carry four oxygen molecules.
Where in the body would you find a low partial pressure of oxygen?
Respiring tissues
Why are oxygen dissociation curves S-shaped?
- When haemoglobin (Hb) combines with the first O₂ molecule, its shape alters in a way that makes it easier for other molecules to join too.
- But as the Hb starts to become saturated, it gets harder for more oxygen molecules to join.
Haemoglobin is a protein with a quarternary structure.
Explain what this means.
[1 mark]
It is composed of more than one polypeptide chain.
Haemoglobin has a high affinity for oxygen. Explain what this means.
‘Affinity’ for oxygen means ‘tendency to combine with’ oxygen.
When is oxyhaemoglobin formed?
Oxyhaemoglobin is formed in the lungs when oxygen joins to haemoglobin in red blood cells.
What is partial pressure of oxygen (pO₂)?
A measure of oxygen concentration.
When does haemoglobin give up its oxygen more readily?
Haemoglobin gives up its oxygen more readily at higher partial pressures of carbon dioxide (pCO₂).
- When cells respire they produce __________, which raises ________.
- This increases the rate of _____ _____, so the dissociation curve ‘shifts’ _____.
- The saturation of blood with oxygen is lower for a given pO₂, meaning that _____ _____ is being released.
- When cells respire they produce carbon dioxide, which raises pCO₂.
- This increases the rate of oxygen unloading, so the dissociation curve ‘shifts’ right.
- The saturation of blood with oxygen is lower for a given pO₂, meaning that more oxygen is being released.
What affects oxygen unloading?
Carbon dioxide concentration.
Organisms that live in environments with a low concentration of oxygen have haemoglobin with a __________ for oxygen than human haemoglobin.
Organisms that live in environments with a low concentration of oxygen have haemoglobin with a higher affinity for oxygen than human haemoglobin.
Organisms that are very active and have a high oxygen demand have haemoglobin with a __________ for oxygen than human haemoglobin.
Organisms that are very active and have a high oxygen demand have haemoglobin with a lower affinity for oxygen than human haemoglobin.
Name all the blood vessels entering and leaving the heart.
- Pulmonary vein (oxygenated blood to the heart)
- Pulmonary artery (deoxygenated blood to lungs)
- Aorta (oxygenated blood to the body)
- Vena Cava (deoxygenated blood to the heart)
List four types of blood vessel.
- Arteries
- Arterioles
- Veins
- Capillaries
Explain why water returns to the capillary at the venule end of the capillary bed.
- The water potential at the venule end is lower than the water potential in the tissue fluid…
- …due to the fluid loss and an increasing concentration of plasma proteins in the capillaries.
- This means that some water re-enters the capillaries at the venule end by osmosis.
Describe two structural features of an artery and explain how each feature relates to its function.
[4 marks]
- They have elastic tissue in the walls…
- …so they can stretch and recoil as the heart beats, which helps maintain the high pressure.
- The inner lining (endothelium) is folded…
- …so that the artery can expand when the heartbeat causes a surge of blood.
At the arteriole end of the capillary bed, the hydrostatic pressure is 5.1 kPa in a capillary bed and 0.13 kPa in the space around the cells.
Explain the effect this has on the movement of fluid between the capillary and cell space.
[2 marks]
- The hydrostatic pressure in the capillary is greater than the hydrostatic pressure in the spaces around the cells,…
- …so fluid moves out of the capillary and into spaces around the cells.
Describe a structural feature of a vein and explain how the feature relates to its function.
- Veins contain valves…
- …to stop the blood flowing backwards.
What are arterioles?
Arterioles are smaller arteries that control blood flow from arteries to capillaries.
How are capillaries adapted for efficient diffusion?
- They’re always found near cells in exchange tissues, so there’s a short diffusion pathway.
- Their walls are only one cell thick, which also shortens the diffusion pathway.
- There are a large number of capillaries, to increase surface area for exchange.
Which side of the heart carries oxygenated blood?
The left side pumps oxygenated blood to the whole body.
Explain the purpose of the semi-lunar valves.
The semi-lunar valves stop blood flowing back into the heart after the ventricles contract.
Name the blood vessel that carries blood from the lungs to the heart.
Pulmonary vein
Give three factors that can increase the risk of developing cardiovascular diseases.
- High blood cholesterol and poor diet
- Cigarette smoking
- High blood pressure
