Haemoglobin Flashcards
Binding of one molecule of oxygen to haemoglobin makes it easier for a second oxygen molecule to bind.
Explain why.
Binding of first oxygen changes tertiary / quaternary (structure) of haemoglobin;
Ignore ref. to ‘positive cooperativity’ unqualified
Ignore ref. to named bonds
Accept conformational shift caused
- Creates / leads to / uncovers second / another binding site
OR
Uncovers another iron / Fe / haem group to bind to;
The doctor also wanted to know how many white blood cells per mm3 there were in a different sample of blood. To do this he first diluted the sample by a factor of 20 times. He then made the white blood cells clearly visible by using a stain that makes nuclei appear dark blue.
(d) When counting white blood cells, the doctor only diluted the blood sample by a factor of 20 times, instead of 200 times when counting red blood cells.
Suggest why he only diluted the sample by a factor of 20 times.
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(1)
(e) Explain how the stain allowed the doctor to count the white blood cells amongst all the red blood cells.
There are fewer white cells, so no need to dilute (further to see enough);
Accept converse of too few to see if greater dilution / at 200 times
Do not accept ref. to numbers of red and white cells unqualified
Ignore ref. to white cells larger
1
(e) White cells have a nucleus (that stains but red cells do not);
Explain the advantage of the curve for fetal haemoglobin being different from the curve for adult haemoglobin.
fetal haemoglobin has higher affinity for oxygen / takes up oxygen
(becomes saturated) at lower partial pressure;
at partial pressures when adult haemoglobin dissociates fetal
haemoglobin takes up oxygen
Explain the advantage of this change in position
1
(ii) haemoglobin dissociates / unloads more readily /
more oxygen delivered to cell / muscles / respiring tissue;
at a particular partial pressure more oxygen is released;
Explain how a change in pH from 7.4 to 7.2 affects the supply of oxygen by haemoglobin to the tissues.
more oxygen unloaded / given up / affinity decreased / reduced saturation; oxyhaemoglobin dissociates at higher oxygen concentration / partial pressure / more oxygen unloaded at the same ppO2;
Explain what causes the pH to be reduced from 7.4 to 7.2 in a tissue.
(aerobic) respiration will produce carbon dioxide / anaerobic respiration produces lactate;
carbon dioxide dissolves in blood forming acid;
increases hydrogen ion concentration;
here is less oxygen at high altitudes than at sea level.
(i) People living at high altitudes have more red blood cells than people living at sea level. Explain the advantage of this to people living at high altitude.
More haemoglobin;
So can load / pick up more oxygen (in the lungs);
Q Second mark point must relate to idea of loading oxygen. Answers referring only to transport of oxygen should not be credited this mark.
The change to the dissociation curve is one of a number of ways in which the total oxygen supplied to muscles is increased during exercise. Give two other ways in which the total oxygen supplied to muscles during exercise is increased.
increased depth / rate / pulmonary ventilation;
increase stroke volume / heart rate / Q increases blood flow rate;
arterioles [Accept artery] supplying the muscles
dilate / vasodilation / greater proportion of blood flow to the muscles;
What is meant by the term partial pressure
It is a measure of the concentration of a gas
(in a mixture of gases or a liquid);
Explain the differences between the figures shown in Table 1 for rest and exercise.
muscle contraction causes increased respiration;
increased CO2 production lowering blood pH / lactate released
lowering blood pH;
increased heat released therefore increased temperature;
increased O2 consumption lowering tissue PO2;
Does enriching inspired air with oxygen have any effect on the amount of oxygen reaching the tissues? Support your answer with evidence from the graph and Table 2.
Nearly all O2 is transported by haemoglobin / v. little transported in plasma;
EITHER
Haemoglobin is (nearly) fully saturated with O2 at the alveoli both at
rest and when exercising;
Therefore no (very little) further increase is possible;
OR
Haemoglobin is only 95% saturated with oxygen at the alveoli;
Therefore enriching inspired / air with oxygen will raise this to 100%;
Erythropoietin (EPO) is a substance produced in the body. It increases the production of red blood cells. Synthetic EPO is made artificially. It is used to treat patients who have a form of anaemia in which there is a reduced number of red blood cells. Scientists investigated the effect of synthetic EPO on volunteers with this form of anaemia.
- The scientists injected synthetic EPO in a salt solution into patients in the experimental groups. They also set up control groups.
- They gave the different experimental groups different doses of synthetic EPO and different lengths of treatment.
- At the beginning and end of the treatment, the scientists measured each patient’s haemoglobin concentration. From these measurements, they calculated the mean increase in haemoglobin concentration.
Suggest how the control groups should have been treated in this investigation
Given (only) salt solution;
(Otherwise) treated the same way;
Some athletes have used synthetic EPO as a performance enhancer. Explain how synthetic EPO may improve performance in long-distance events.
_______________________________________________________more red blood cells
More haemoglobin / more red blood cells;
(More) oxygen can be absorbed / transported (for) respiration / to respiring tissues / cells;
(More) energy released / more ATP for muscle contraction;
Delays anaerobic respiration / delays build up of
lactate / lactic acid;
Athletes may be tested to see if the concentration of EPO in their blood is above normal. Suggest how scientists determine the normal concentration of EPO in blood.
Large sample / wide range (of individuals tested);
Random (sampling);
Tested at different times / more than once;
Mean / average value determined;
Idea of establishing a range for the normal concentration / reference
to use of standard deviation;
Synthetic EPO can increase blood pressure. Suggest
Blood thicker / denser / more viscous / more ‘concentrated’ / heart
contraction greater / increases volume of blood;
