Transport of Gases Flashcards
What is blood?
An aqueous medium which allows for gas exchange and the delivery of important molecules such as glucose and oxygen
How is blood a tissue?
Blood is a tissue comprising blood cells suspended in a straw-coloured fluid called plasma
What is plasma made of?
90% water, with a range of dissolved materials
What dissolved materials are in plasma?
-glucose
-amino acids
-salts
-hormones
-urea
-plasma protein
What are the 4 components that make up the blood?
-plasma- liquid part of the blood
-wbc- involved in immune system
-platelets- involved in blood clotting
-rbc- involved in carrying oxygen
What does plasma contain?
digested food products e.g. glucose and amino acids
What does plasma transport and distribute?
-Transports hormones, antibodies, and other proteins
-Distributes heat around the body
What are the three types of blood cell?
-Leucocytes
-Thrombocytes
-Erythrocytes
What are leucocytes?
White blood cells
what are thrombocytes?
Platelets
what are erythrocytes?
Red blood cells
What leucocytes be divided into?
Two groups of immune cells:
-granulocytes
-agranulocytes
What are granulocytes?
-They have granular cytoplasm and lobed nuclei
-Their function is to engulf pathogens by phagocytosis
What do agranulocytes produce and are their features?
-produce antibodies and antitoxins
-have clear cytoplasm and spherical nucleus
What are thrombocytes (platelets) involved in?
-Blood clotting
what are erythrocytes filled with?
the pigment haemoglobin
What are the three important features in erythrocytes for?
theses features allow them to efficiently transport oxygen
What is the first important feature which allows erythrocytes to efficiently transport oxygen?
They are biconcave discs giving them a large surface area so more oxygen can diffuse across the membrane
What is the second important feature which allows erythrocytes to efficiently transport oxygen?
Mammalian red blood cells have no nucleus so there is more room for haemoglobin which means more oxygen can be transported
What is the third important feature which allows erythrocytes to efficiently transport oxygen?
They are flexible so that they can fit through the very narrow lumen of the capillaries
What is the structure of haemoglobin?
-complex globular protein, with a quaternary structure consisting of four folded polypeptide chains
what is at the centre of each polypeptide? (haemoglobin)
-a haem group which contains (Fe2+)
-each haem group is a binding site for one oxygen
What can one molecule of haemoglobin bind to, to form oxyhaemoglobin?
four oxygen molecules
What intermolecular bonds can be found in haemoglobin?
-hydrogen
-ionic
-disulphide
What is the equation for the reversible reaction between haemoglobin and oxygen?
4O2 + Hb <—> HbO8
What is affinity?
The degree to which one molecule (haemoglobin) is chemically attracted to another molecule (oxygen)
what is saturation?
The percentage of oxygen bound to haemoglobin
what is association/loading?
The uptake of oxygen by haemoglobin to form oxyhaemoglobin at the lungs
what is dissociation/unloading?
The release of oxygen at the respiring tissues to form haemoglobin
How is Oxyhaemoglobin formed?
-Oxygen diffuses into the red blood cells and associates with haemoglobin
How is oxygen concentration measured?
by partial pressure (kPa)
what happened when the partial pressure of oxygen is high? (e.g. in the lungs)
haemoglobin has a high affinity for oxygen and so oxygen associates with haemoglobin to form oxyhaemoglobin
what happens when the partial pressure of oxygen is low? (e.g in the respiring tissues)
Haemoglobin has a low affinity for oxygen and so oxygen dissociates from oxyhaemoglobin, forming haemoglobin
In which way is the shape of the haemoglobin dissociation line different from the theoretical line? (oxygen dissociation curve)
-The haemoglobin line is s shaped
-haemoglobin line rises most deeply between 2 and 7 kPa (is steeper in the middle)
-theoretical shows no flattening at the top
-Haemoglobin line shows higher saturation throughout
what does cooperative binding describe?
The ease with which a haemoglobin molecule binds a second and then third oxygen molecule, compared with the first and fourth
what is the explanation of cooperative binding?
•As haemoglobin is a protein, any molecule that associates with it will cause a slight change in shape. Once the first molecule of O2 has associated with haemoglobin, it causes a change in the shape that makes the second and third binding site more available, increasing haemoglobin affinity for oxygen. The 2nd and 3rd oxygen molecule associate more easily than the first.
•It is then more difficult for an oxygen molecule to associate with the last binding site. Therefore the binding of oxygen to haemoglobin is not directly proportional to oxygen concentration.
•As a result the line of the oxygen dissociation curve is not straight but instead a sigmoid curve (S-shaped)
When is haemoglobin affinity for oxygen high?
At high partial pressures of oxygen.
where does haemoglobin load (associated) oxygen in the lungs and what happens after?
-where oxygen partial pressure (ppO2) is high
-Haemoglobin becomes saturated with oxygen and forms of oxyhaemoglobin
-oxygen is transported in this form to respiring tissues, such as muscles
what does it mean as oxygen affinity decreases as oxygen partial pressure decreases?
this means it is readily released to meet respiratory demands
what does a very small reduction in oxygen partial pressure lead to?
oxygen unloading (dissociating) from oxyhaemoglobin rapidly
what happens at a very low oxygen partial pressure?
-it is difficult for haemoglobin to load oxygen
-in inspiring tissues the oxygen partial pressure is low because oxygen is being used up in aerobic respiration
-The oxygen then unloads from oxyhaemoglobin (dissociates)
What does a pulse oximeter do?
-estimates oxygen saturation in your blood
-it does so by sending infrared light into capillaries in your finger, then it measures how much light is reflected off the gases
Why is the saturation of haemoglobin measured in a healthy person 98/99% and not 100%?
-some oxygen is used by respiring cells of the alveoli
-The rate of the blood flow through the pulmonary capillaries is still too fast for oxygen to diffuse into the blood
what association does foetal haemoglobin have and what does this mean?
-It has an oxygen dissociation curve shifted to the left of the adult curve
-this means it has a higher affinity for oxygen and therefore can load oxygen from the mother’s blood at all partial pressures of oxygen.
why doesn’t a baby retain its foetal haemoglobin once it’s born?
-Foetal haemoglobin has a higher oxygen affinity, so not enough oxygen would be released to respiring tissue of an adult
-If female, when having own children the adult needs its haemoglobin to have lower affinity than the foetal Hb.
Where do llamas live and what does this mean?
-Llamas live at high altitude
-with an increase in altitude there is a drop in atmospheric pressure and therefore a reduction in the partial pressure of oxygen
what does a llama have to compensate a reduction in oxygen partial pressure?
-A Llama’s haemoglobin has a higher affinity for oxygen and therefore picks up oxygen readily at the lungs
-The curve is shifted to the left
why do animals live in high altitude also have more red blood cells?
More haemoglobin so more oxygen can be loaded and transported
where do lugworms live?
-In burrows in the sand on the seashore
where do lugworms get oxygen from?
They absorb oxygen from the seawater they pump through their burrows
what do lugworms have in order to cope with the low oxygen concentration of seawater?
they have a dissociation shifted to the left- higher affinity for oxygen- so the haemoglobin more readily takes up oxygen
what is myoglobin?
A tertiary structured protein that is more stable than haemoglobin
what does myoglobin act as?
-An oxygen store in muscle tissue
where is myoglobin’s dissociation curve?
-The curve is very far to the left of haemoglobin
what is myoglobin’s percentage oxygen saturation at every partial pressure of oxygen?
it has a higher percentage oxygen saturation than haemoglobin at every partial pressure of oxygen
what happens if oxygen partial pressure becomes very low in myoglobin?
Oxymyoglobin unloads it’s oxygen
what would cause the partial pressure of oxygen to become very low? (myoglobin)
Vigourous exercise
what is the bohr effect?
-When the partial pressure of carbon dioxide is high (due to carbon dioxide production in respiring tissues, e.g. contracting muscle) the conditions become more acidic.
-This causes haemoglobin to change shape slightly and so haemoglobin now has a lower affinity for oxygen, unloading this oxygen to the respiring tissues more readily.
What happens to the s-shaped curve to represent the bohr effect?
The s-shaped curve is shifted to the right
What are the three ways carbon dioxide is transported in the blood?
-10% binds to haemoglobin as carbamino-haemoglobin
-5% is dissolved in plasma
-85% of the carbon dioxide carried in the blood is converted to hydrogen carbonate ions (HCO3-) and transported in plasma
what is the process leading to the chloride shift?
CO2 from respiring cells diffuses into plasma, then into red blood cells.
• CO2 reacts with water to produce carbonic acid. This reaction is catalysed by the enzyme carbonic anhydrase.
CO2 + H20 → H, COz
• The carbonic acid dissociates into H* + CO3 (hydrogen carbonate) ions.
• The HCOz ions diffuse down their concentration gradient into plasma.
• The COz ions combine with Na ions in plasma to form sodium hydrogen carbonate (NaHCOz).
• In the red blood cells, the accumulation of H+ ions from the dissociation of carbonic acid causes a fall in pH (cytoplasm becomes more acidic).
• This alters the haemoglobin, reducing its affinity for oxygen. H+ combine with haemoglobin to form haemoglobinic acid (HHb). This releases the oxygen:
H++ HbOg → HHb + 40г
• The released oxygen diffuses out of red blood cells into the respiring tissues.
• Movement of negatively charged ions (HCOz) out of red blood cells is balanced by the movement of chloride ions (Cl-) into the red blood cells from the plasma by facilitated diffusion.
• This maintains the electrochemical neutrality of the red blood cells and is known as the CHLORIDE SHIFT.
What explains the bohr effect?
the formation of carbonic acid and subsequent fall in pH inside the red blood cells
how are capillaries adapted to be the site of exchange between the blood and body cells?
-Thin- one cell thick, permeable walls
-Large SA for exchange of materials
-Blood flows slowly through capillaries allowing time for exchange of materials
How was tissue fluid formed?
At any capillary bed, fluid (water and small substances) is forced out through gaps between cells and the capillary walls, forming tissue fluid.
What does tissue fluid do?
Bathes cells and allows exchange of gases and nutrients
what molecules are required by cells?
Glucose, amino acids, oxygen
What are the removed waste substances?
-urea
-CO2
What happens at the arterial end of capillary?
• Blood is under pressure because contraction of the left ventricle. This creates a high hydrostatic pressure and forces fluid through gaps in the capillary walls.
• The outward flow of fluid is opposed by osmotic pressure (water trying to move back into the blood by osmosis).
• However, as the hydrostatic pressure is greater than the osmotic pressure, there is a net flow of fluid out of the blood.
• Molecules dissolved in the tissue fluid then move by diffusion and facilitated diffusion into the cells (down their concentration gradient).
What happens at the venous end of capillary?
• Tissue fluid contains waste substances that have diffused out of cells. These can diffuse back into the blood in the capillaries down a concentration gradient.
• There is now a much lower hydrostatic pressure due to friction between the blood and the capillary wall and due to the lower volume of fluid in the capillaries.
• Water potential in the blood is lowered due to the presence of plasma proteins.
Therefore, osmotic pressure is now greater than hydrostatic pressure and so there is a net movement of water back into the blood in the capillaries by osmosis.
Approximately 90% of tissue fluid flows back into capillaries.
what happens to tissue fluid that does not return to the capillaries at the Venous end of a capillary bed?
-10% drains into lymphatic capillaries, found amongst the tissues
-the remaining fluid, lymph, eventually returns to the blood in the circulatory system
What is the lymphatic system involved in?
-absorption of lipids in the small intestine
-The formation of the lymphocytes and the prevention of disease
What does accumulation of fluid in the tissues cause?
-Swelling under the skin (oedema)
what is the explanation for the symptom of oedema?
-fewer plasma proteins in the blood, which raises water potential of the blood plasma
-this reduces the water potential gradient between the blood and the blood tissue (hydrostatic pressure is greater than osmotic pressure)
-so less water is absorbed into the blood by osmosis
