3.4 - Mass Transport Flashcards
Describe the structure of haemoglobin.
Globular, water soluble. Consists of four polypeptide chains, each carrying a haem group (quaternary structure).
Describe the role of haemoglobin.
Present in red blood cells. Oxygen molecules bind in the haem groups and are carried around the bogy to where they are needed in respiring tissues.
Name the three factors affecting oxygen-haemoglobin binding.
- Partial pressure/concentration of oxygen
- Partial pressure/concentration of CO2
- Saturation of haemoglobin with oxygen.
How does saturation of haemoglobin with oxygen affect oxygen-haemoglobin binding?
It s hard for the first oxygen molecule to bind. Once it does, it changes its shape to make it easier for the second and third molecules o bind, known as positive cooperativity. It is then slightly harder for the fourth oxygen molecule to bind because there is a low chance of finding a binding site.
How does partial pressure of oxygen affect oxygen-haemoglobin binding?
As partial pressure of oxygen increases, the affinity of haemoglobin for oxygen also increases, so oxygen binds tightly to haemoglobin. When partial pressure is low, oxygen is released from haemoglobin.
Explain why oxygen binds to haemoglobin in the lungs.
- Partial pressure of oxygen is high.
- Low concentration of CO2 in the lungs, so affinity is high.
- Positive cooperativity, after the first oxygen molecule
binds, binding of subsequent molecules is easier.
Explain why oxygen is released from haemoglobin in the respiring tissues.
- Partial pressure of oxygen is low.
- High concentration of CO2 in respiring tissues, so affinity
decreases.
What do oxyhaemoglobin dissociation curves show?
Saturation of haemoglobin with oxygen (in %), plotted against partial pressure of oxygen (in kPA). Curves further to the left show the haemoglobin has a higher affinity for oxygen.
How does carbon dioxide affect the position of an oxyhaemoglobin dissociation curve?
Curve shifts to the right because haemoglobin’s affinity for oxygen has decreased.
Name 3 common features of a mammalian circulatory system.
- Suitable medium for transport, water-based to allow
substances to dissolve. - Means of moving the medium and maintaining pressure
throughout the body, such as the heart. - Means of controlling flow so it remains unidirectional, such as
valves.
Relate the chambers in the heart to their function>
Atria: thin-walled and elastic, so they can stretch when filled with blood.
Ventricles: thick muscular walls pump blood under high pressure. The left ventricle is thicker than the right because it has to pump blood all the way around the body.
Relate the structure of the blood vessels to their function.
- Arteries have thick walls to handle blood under high pressure
without tearing, and are muscular and elastic to control blood flow. - Veins have thin walls due to low pressure, therefore requiring valves
to ensure blood doesn’t flow backwards. Have less muscular and
elastic tissue as they don’t have to control blood flow.
Why are two pumps needed (left and right) instead of one?
To maintain blood pressure around the whole body. When blood passes through the capillaries of the lungs, the pressure drops sharply and therefore would not be flowing strongly enough to continue around the whole body. Therefore it is returned to the heart to increase the pressure.
Describe what happens during cardiac diastole.
The heart is relaxed. Blood enters the atria, increasing the pressure and pushing open the atrioventricular valves. This allows blood to flow into the ventricles. Pressure in the heart is lower than in the arteries, so semi-lunar valves remain closed.
Describe what happens during atrial systole.
The atria contract, pushing any remaining blood into the ventricles.
Describe what happens during ventricular systole.
The ventricles contract. The pressure increases, closing the atrioventricular valves to prevent backflow, and opening the semiluna valves. Blood flows into the ateries.
Name the nodes involved in heatt contraction and where they are situated.
- Sinoatrial node (SAN) = wall of right atrium.
- Atrioventricular node (AVN) = in between the two atria.
What does myogenic mean?
The heart’s contraction is initiated from within the muscle itself, rather than by nerve impulses.
Explain how the heart contracts.
- SAN initiates and spreads impulse across the atria, so they contract.
- AVN receives, delays and then conveys the impulse down the bundle of His.
- Impulse travels into the Purkinje fibres which branch across the ventricles, so they contract from the bottom up.
Why does the impulse need to be delayed?
If the impulse spread straight from the atria into the ventricles, there would not be enough time for all the blood to pass through and for the valves to close.
How is the structure of capillaried suited to their function?
- Walls are only one cell thick; short diffusion pathway.
- Very anrrow, so can permeate tissues and red blood cells can lie flat against the want effectively delivering oxygen to tissues.
- Numerous and highly branched, providing a large surface area.
What is tissue fluid?
A watery substance containing glucose, amino acids, oxygen, and other nutrients. It supplies these to the cells, while also removing any waste materials.
How is tissue fluid formed?
As blood is pumped through increasingly small vessels, this created hydrostatic pressure which forces fluid out of the capillaries. It bathes the cells, and then resturns to the capillaries when the hydrostatic pressure is low enough.
How is water transported in plants?
Through xylem vessels; long, continuous columns that also provide structural support to the stem.
