Mass Transport Flashcards
Why do large organisms have a transport system?
Multicellular organisms, like mammals and plants, have a small surface area to volume ratio so they need a specialised mass transport system to carry molecules between specialised exchange surfaces and cells
Describe haemoglobin
- Found in erythrocytes
- Protein with quaternary structure
- 2 alpha and 2 beta sub units, each contains a polypeptide chain and an Fe2+ haem group
- High affinity for oxygen
- Can bind to 4 oxygen molecules to form oxyhaemoglobin (this is a reversible reaction)
What is the oxyhaemoglobin dissociation curve described as?
Sigmoidal curve
Describe the sigmoidal curve at low oxygen partial pressure
The haemoglobin does not easily bind to the oxygen. This is because the haem groups are in the centre of the haemoglobin which makes it difficult for the oxygen to bind with it. This results in a low saturation level at low oxygen partial pressures i.e. low affinity
Describe the sigmoidal curve as the oxygen partial pressure increases
The diffusion gradient into the haemoglobin increases. This means that eventually an oxygen molecule will associate with one of the haem groups. This results in a change in the shape of the haemoglobin molecule and makes it easier for more oxygen molecules to associate with the other haem groups, therefore the gradient of the curve increases as the oxygen partial pressure does. However, it is difficult for all the haemoglobin molecules to become 100% saturated even at high oxygen partial pressures. This is because it is difficult for the last oxygen to diffuse and associate with the 4th haem group
Describe carbon dioxide concentration and how it affect the dissociation of oxyhaemoglobin to form haemoglobin
At higher partial pressures of carbon dioxide oxygen unloads more readily.
When cells respire they produce carbon dioxide, which raises pCO2. This increases the rate at which oxyhaemoglobin dissociates to form haemoglobin and oxygen . The dissociation curve therefore shift to the right. This is called the Bohr Effect.
The Bohr Effect therefore results in more oxygen being released when more carbon dixoide is being produced. This means that when exercising the muscles can be supplied with more oxygen for continued aerobic respiration
What must haemoglobin be like at low oxygen environments?
Must have a higher affinity for oxygen than human haemoglobin. This is because there isn’t much oxygen available so the haemoglobin has to be very good at loading any oxygen available. The dissociation curve moves to the LEFT of a human’s E.g. lugworm
What must haemoglobin be like at high activity levels?
The haemoglobin must have a lower affinity for oxygen than human haemoglobin. This is because they need to be able to unload oxygen easily, so that it’s available to use. The dissociation curve moves to the RIGHT of a human’s E.g. hawk
How does the size of the mammal affect the haemoglobin?
Small mammals tend to have higher surface area to volume ratios than larger mammals. This means they lose heat quickly, so have a higher metabolic rate to help them keep warm - therefore they have a high oxygen demand. They have haemoglobin with a lower affinity oxygen than human haemoglobin. This is because they need their haemoglobin to easily unload oxygen, so that its available to use. The dissociation curve is to the RIGHT of a human’s. e.g. rat
Mammals have a closed, double circulatory system, what does this mean?
Closed - blood is confined to vessels
Double - blood passes twice through the heart for each complete circuit of the body
Where does the pulmonary artery carry blood from and to?
From heart to lungs
Where does the pulmonary vein carry blood from and to?
From lungs to heart
Where does the aorta carry blood from and to?
From heart to body
Where does the vena cava carry blood from and to?
From body to heart
Where does the renal artery carry blood from and to?
From body to kidneys
Where does the renal vein carry blood from and to?
From kidneys to heart
What is the word ‘hepatic’ associated with?
Liver
Which side of the heart pumps deoxygenated blood to the lungs?
Right
Which side of the heart pumps oxygenated blood to the whole body?
Left
Which ventricle has the thicker muscular wall and why?
The left ventricle has a thicker muscular wall because the ventricle must contract very hard to pump blood all around the body
What does the septum do?
Separates the two sides of the heart so oxygenated blood and deoxygenated blood does not mix
Describe the structure of arteries and arterioles
Arteries carry blood from the heart to the rest of the body. These then divide into arterioles
- Lumen is narrow to maintain the blood pressure
- Collagen fibres and fibrous means the thick wall can withstand high pressure.
- The elastic tissue allows the wall to stretch and then recoil. This maintains the diastolic blood pressure
- The endothelium is smooth to reduce friction and is also folded so it can unfold when the artery stretches
- Smooth muscle allows contraction and vasoconstriction, this narrows the lumen of the artery.
Describe the structure of the veins
Veins carry blood back to the heart
- Lumen is large to ease the flow of the blood
What is meant by the term systole?
Contraction of the cardiac muscle
What is meant by the term diastole?
Relaxation of the cardiac muscle
How long does the cardiac cycle last and what heart rate does this give?
0.8 seconds
75 beats per min
What is the first stage of the cardiac cycle?
- Atria fill with blood
- Atria contact decreasing the volume of the atria and increasing the pressure in the chambers - blood is squeezed into ventricle via atrioventricular valve
What is the second stage of the cardiac cycle?
- Ventricles contract decreasing their volume and increasing the pressure inside their chambers
- The pressure inside the ventricle becomes higher than the pressure inside the atria forcing the atrioventricular valves shut to prevent back flow.
- The pressure in the ventricles is also higher than that of the arteries which forces the semi-lunar valves open
What is the third stage of the cardiac cycle?
- Ventricles and atria both relax (diastole)
- The higher pressure in the arteries than ventricles causes the semi lunar valves to close to prevent the back flow of blood into the ventricles
- Atria fill with blood
- The cycle starts again
When are valves closed?
When the pressure beneath the valve is greater than above it
What is the lub-dub sound of the heart caused by?
The closing of the atrioventricular valve and the closing of the semi-lunar valve
When looking at a graph on the cardiac cycle what mnemonic should you remember to show if the valves are open or closed?
COCO
On an electrocardiogram (ECG) what does the ‘P’ show?
Excitation of the atria (atrial systole)
On an ECG what does the ‘Q,R,S’ show?
Excitation of the ventricles (ventricular systole)