Mass transport in animals and plants Flashcards
What protein structure does haemoglobin have?
Quaternary - 4 polypeptide chains each containing a haem group, globular protein
What is the equation for when haemoglobin is loaded with oxygen?
Haemoglobin (Hb) + oxygen (O2) -> oxyhemoglobin (HbO8)
What are the names for attachment and detachment of O2?
loading/unloading
association/dissociation
What is the difference between high and low affinity haemoglobin?
high affinity = oxygen is taken up more easily but released less readily
low affinity = oxygen is taken up less easily but released more readily
What is the role of haemoglobin?
Due to the 4 haem (Fe2+) groups, haemoglobin is able to bind to 4 oxygen molecules to form oxyhemoglobin
- it will readily associate with oxygen at the surface where gas exchange takes place
- readily dissociate from oxygen at the tissues requiring it
Why do different haemoglobin have different affinities for oxygen?
slightly different tertiary and quaternary structure and hence different oxygen binding properties
Explain the shape of an oxygen dissociation curve?
- the shape of haemoglobin makes it difficult for the first oxygen molecule to bind so initially a shallow gradient
- binding of the first oxygen molecule changes the quaternary structure of the haemoglobin, making it easier for the other subunits to bind to O2
- graph flattens off when 3 binding sites are occupied because it is less likely that a single O2 molecule will find an empty site to bind to
What do oxygen dissociation curves show?
Oxygen affinity
- the further to the left, the greater the oxygen affinity (during rest)
- the further to the right, the lower the oxygen affinity (during exercise)
What is the effect of CO2 on oxygen affinity?
- haemoglobin has reduced affinity for oxygen in the presence of carbon dioxide, so reduces oxygen more readily
eg. in muscles, CO2 concentration is high during respiration. This reduces oxygen affinity so it can be more readily released for respiration
How does pH help to load and unload oxygen?
- at the gas exchange surface, CO2 is constantly removed
- pH is slightly raised due to low CO2 concentration
- higher pH changes the shape of haemoglobin into one that enables it to load oxygen more readily
- in tissues, CO2 is produced by respiring cells
- CO2 is acidic in solution, so pH of blood within the tissues is lowered
- lower pH changes the shape of haemoglobin into one with a lower affinity for oxygen
- haemoglobin releases oxygen to respiring tissues
How is more oxygen produced during respiration due to affinity?
- the higher rate of respiration
- the more CO2 produced by tissues
- the lower the pH
- the greater the shape change of haemoglobin
- the more readily oxygen is unloaded
- the more oxygen is available for respiration
(known as the Bohr effect)
How is oxygen affinity different for insects and llamas?
- insects have a very rapid rate of respiration and high metabolism, and so dissociation curve lies to the right of humans due to low O2 affinity
- llamas live at high altitudes with low atmospheric pressure, so partial pressure of oxygen is lower. It is therefore more difficult to load haemoglobin with oxygen so the dissociation curve lies to the left of humans, with a much higher O2 affinity
Why must blood pass through the heart twice in one circuit?
- when blood passes through the lungs, the pressure is reduced. If it were to pass immediately through to the body, the low pressure would make circulation very slow. Blood is therefore returned to the heart to boost its pressure before being circulated to the rest of the tissues
What is the pathway taken by a RBC from the vena cava to the body?
vena cava, right atrium, right ventricle, pulmonary artery, lungs, pulmonary vein, left atrium, left ventricle, aorta, body
Why does the left ventricle have a thicker muscle wall?
it must contract to create enough pressure to pump blood around the rest of the body
Which valves are between the atria and ventricles, and what is their purpose?
Left and right atrioventricular valves, prevent back flow of blood
Which side of the heart does oxygenated blood pass through?
Left
What are the 3 stages of the cardiac cycle?
- diastole
- atrial systole
- ventricular systole
What happens during diastole?
Relaxation of the heart
Blood enters atria and ventricles from pulmonary veins and vena cava. As atria fills, pressure rises causing atrioventricular valves to open and blood to flow into ventricles. Pressure is lower in ventricles than in the aorta and pulmonary artery, so semi-lunar valves close. Atria and ventricles are relaxed
What happens during atrial systole?
Contraction of the atria
Contraction of atrial walls and recoil of ventricle walls forces the remaining blood into ventricles from the atria. The ventricle muscles remain relaxed