mass transport in animals Flashcards
what is the role of haemoglobin and where is it found?
-it is found in red blood cells
-role is to carry oxygen around the body
-there are chemically similar types of haemoglobin found in other organisms, which carry out the same function
-it is found in earthworms, starfish, some insects, some plants and some bacteria
what is the structure of haemoglobin?
-large protein with a quaternary structure
-made up of four polypeptide chains
-each chain has a haem group which contains and iron ion and gives haemoglobin its red colour
-each molecule can carry four oxygen molecules
when is oxyhaemoglobin made?
in the lungs, when oxygen joins to haemoglobin during gas exchange
write the haemoglobin - oxyhaemoglobin reversible reaction.
associating/loading
Hb + 4O2 <–> HbO8 disassociating/ unloading
what does ‘affinity for oxygen mean’ and what is haemoglobins?
the tendency a molecule has to bind with oxygen.
haemoglobins affinity varies depending on the conditions its in, including the partial pressure of oxygen (pO2)
what does partial pressure of oxygen (pO2) mean?
a measure of oxygen concentration
the greater the concentration of dissolved oxygen in cells, the higher the partial pressure
relate partial pressure of oxygen to haemoglobin.
as pO2 increases, haemoglobins affinity for oxygen also increases.
-oxygen loads onto haemoglobin to form oxyhaemoglobin where there’s a high pO2
-oxyhaemoglobin unloads its oxygen where there’s a lower pO2
describe these 4 features at the alveoli and respiring tissues:
-oxygen concentration
-pO2
-affinity for oxygen
-loads or unloads
alveoli:
-HIGH oxygen concentration
-HIGH pO2
-HIGH affinity
-oxygen LOADS
respiring tissues:
-LOW oxygen concentration
-LOW pO2
-LOW affinity
-oxygen UNLOADS
what does an oxygen dissociation curve show?
how saturated the haemoglobin is with oxygen at any given partial pressure.
the affinity for haemoglobin for oxygen affects how saturated the haemoglobin is
what are the two axis on an oxygen dissociation curve?
Y= %saturation of haemoglobin with oxygen
X= partial pressure of O2 / kPa
why is an oxygen dissociation curve an ‘s’ shape?
because the saturation of haemoglobin can also affect the affinity
how does the saturation of haemoglobin affect its affinity?
-when haemoglobin binds with the first oxygen molecule, its shape alters in a way that makes it easier for the other O2 molecules to bind
-however as the haemoglobin gets too saturated, it gets harder for oxygen molecules to join
-this means the curve is a bit steeper in the middle where its easy for oxygen molecules to join and shallower bits at the start and end
how does the partial pressure of carbon dioxide (pCO2) affect oxygen unloading and how does this affect the dissociation curve?
-haemoglobin gives up more oxygen readily at a higher pCO2
-when cells respire they produce CO2 which raises the pCO2 causing more oxygen to be unloaded
-the dissociation curve ‘shifts’ to the right
-this is called the Bohr effect
what type of haemoglobin do organisms in low oxygen environments (e.g. lugworms) have and how does this effect the dissociation curve?
-haemoglobin with a higher affinity for oxygen
-this is because there is less oxygen available, so the haemoglobin needs to be good at loading any available
-the dissociation curve is to the left of ours
what type of haemoglobin do organisms in high activity level (e.g. birds) environments have and how does this effect the dissociation curve?
-has a lower affinity for oxygen
-their haemoglobin needs to be able to unload oxygen easily so its available for them to use
-the dissociation curve sits to the right of humans
what type of haemoglobin do small organisms have (e.g. rats) and how does this affect the dissociation curve?
-tend to have a higher surface area to volume ratio meaning they lose heat quickly so have a high metabolic rate to keep them warm, meaning they have a high oxygen demand
-haemoglobin will have a lower affinity for oxygen because it needs to be able to unload oxygen easily
-their dissociation curve sits to the right of a human one
why do multicellular organisms need a circulatory system?
have a low surface area to volume ratio so need a specialised mass transport system to carry raw materials from specialised exchange organs to their body cells
name the 6 vessels in the human circulatory system and where they carry blood from and to.
the PULMONARY ARTERY carries deoxygenated blood from the HEART to the LUNGS
the PULMONARY VEIN carries oxygenated blood from the LUNGS to the HEART
the AORTA carries oxygenated blood from the HEART to the BODY
the VENA CAVA carries deoxygenated blood from the BODY to the HEART
the RENAL ARTERY carries oxygenated blood from the BODY to the KIDNEYS
the RENAL VEIN carries deoxygenated blood from the KIDNEYS to the VENA CAVA
what gives the heart its blood supply?
the left and right coronary arteries
what kind of substances does blood transport around the body?
respiratory gases, products of digestion, metabolic wastes and hormones
what is the structure of arteries and how do these features relate to their function?
-the muscle layer is thick so vasodilation and vasoconstriction can happen
-elastic layer is relatively thick to allow recoil to maintain pressure so blood can get to extremities
-thick wall to prevent bursting under high pressure
-no valves as blood pressure is high
-the inner lining (the endothelium) is folded so the artery can stretch
-they divide into smaller vessels called arterioles
what is the structure of arterioles and how do these feature relate to their function?
-muscle layer is thicker then in arteries to allow more vasodilation and vasoconstriction for control of blood flow to capillaries
-elastic layer is thinner than in arteries and blood pressure is lower so less recoil is required
what is the structure of veins and how do these features relate to their function?
-the overall thickness of the wall is thinner as blood pressure is lower
-muscle layer is relatively thin as there is not need to regulate flow to tissues
-elastic layer is relatively thin as there is no need for recoil
-they contain valves at intervals to prevent backflow of blood as it is under low pressure
what is the structure of capillaries and how do these features relate to their function?
-walls consist mainly of the lining layer (endothelium) so there is a short diffusion distance
-there are numerous of them in capillary beds and they are highly branched for a large surface area
-there are spaces between endothelial cells so there is space for tissue fluid formation and white blood cells to move out
-they have a narrow lumen (7 micrometres) so red blood cells are squeezed close to cells
-narrow diameter so they can penetrate close to exchange surfaces
