correct solutions
Species A lives in water containing a low ppO2, so the curve shows that their Hb has a
higher affinity for O2. This means the Hb becomes fully saturated at a lower ppO2 and
rapidly unloads its oxygen when it passes into tissues to supply sufficient oxygen.
✅✅The graph shows the oxygen haemoglobin dissociation curves for three species
of fish.
Species A lives in water containing a low partial pressure of oxygen. Species C lives in
water with a high partial pressure of oxygen. The oxygen haemoglobin dissociation
curve for species A is to the left of the curve for species C. Explain the advantage to
species A of having haemoglobin with a curve in this position.
Species B has a higher metabolic rate (respires more) than A, so its Hb has a lower
affinity for O2, which means O2 dissociates from the Hb more readily at respiring
tissues. ✅✅Species A and B live in the same place but B is more active. Suggest an
advantage to B of having an oxygen haemoglobin dissociation curve top the right of that
for A.
RBC
Contains haemoglobin
Contains spectrin
No cell wall
Ribosomes are absent
BC
Does not contain haemoglobin
Does not contain spectrin
Peptidoglycan cell wall
70S ribosomes ✅✅Read the following passage.
Use the information from the passage and your own knowledge to answer the following
questions.
Complete the table by giving two ways in which the structure of a red blood cell differs
from the structure of a bacterial cell.
In a mature red blood cell, the ribosomes are absent, so the cell cannot carry out protein
synthesis. ✅✅Haemoglobin is a protein. Explain why a mature red blood cell cannot
make haemoglobin.
They have a larger surface area to volume ratio. All of the inside of a normal RBC is
closer to the surface than in spherical cells, which provides oxygen with a shorter
, diffusion pathway. ✅✅Some people have red blood cells that do not contain spectrin.
These red blood cells are spherical in shape. They also burst more quickly when put in
distilled water.
Explain why more oxygen is taken up by normal red blood cells than by these spherical
cells.
Carbon dioxide is a product, and this reacts with water in the blood plasma to form
carbonic acid (which decreases pH). ✅✅A decrease in the pH of blood plasma
reduces the affinity of haemoglobin for oxygen.
Explain how aerobic respiration in cells leads to a change in the pH of blood plasma.
The more acidic the plasma pH, the more CO2 is being produced, which means higher
rate of respiration. More O2 is needed at the respiring tissue. A reduction in affinity
means O2 dissociates from Hb more readily, so O2 more readily available so tissue
cells can respire. ✅✅What is the advantage to tissue cells of a reduction in the affinity
of haemoglobin for oxygen when the plasma pH decreases.
The shift of the curve to the left means their Hb has a higher affinity for O2 which means
it becomes fully saturated at a lower ppO2 and rapidly unloads its oxygen at respiring
tissues at sufficient value. ✅✅Deer mice are small mammals which live in North
America. One population lives at high altitude and another at low altitude. Less oxygen
is available at high altitude. The graph shows the oxygen haemoglobin dissociation
curves doe the two populations of deer mice.
Explain the advantage for mice living at high altitude in having a dissociation curve
which is to the left of the curve for mice living at low altitude.
Mice have a high metabolic rate, so an insufficient amount of oxygen would be able to
dissociate from Hb with a very high O2 affinity. ✅✅Suggest why it would be a
disadvantage for the curve to be much further left.
Each Hb transports 4 O2. Oxygen diffuses into red blood cells. The partial pressure of
oxygen is high in the alveolar capillaries, so haemoglobin has a high affinity for O2 at a
high ppO2. Haemoglobin becomes fully saturated, forming oxyhaemoglobin, as the red
blood cells pass through the pulmonary capillaries. The haemoglobin has bound its
maximum amount of oxygen and is 98% saturated. The ppO2 in respiring tissues is
much lower. This means haemoglobin has a low affinity for O2 at a low ppO2 and so the
oxyhaemoglobin dissociates to release oxygen. During respiration, there is a high CO2
concentration. This means oxyhaemoglobin dissociates because more CO2 leads to a
lower pH, which means more O2 dissociates as more O2 is needed by respiring tissues.
✅✅Read the following passage.