During one cardiac cycle: • blood enters the heart from the lungs and from the rest of the body • blood leaves the heart to be transported to the lungs and to the rest of the body.

1. (a)Name the blood vessels entering the heart that bring blood from the rest of the body.[1]
2. (b)One phase of the cardiac cycle is ventricular diastole (ventricular relaxation). A number of events occur in the heart during this phase. Outline and explain the events that occur in the heart during ventricular diastole.[4]
3. (c)(i)The cause of the differences between sickle cell haemoglobin and normal haemoglobin is a mutation in the gene that codes for one of the two types of polypeptide found in a haemoglobin molecule. This mutation leads to a change in the mRNA produced during transcription, causing a change in the primary structure of the polypeptide formed. Fig. 3.1 shows some of the changes that occur as a result of this gene mutation. [Figure 3.1] With reference to Fig. 3.1, state: • the base sequence of DNA triplet P • the base sequence of DNA triplet Q • the base sequence of mRNA codon R.[3]
4. (c)(ii)Name the type of polypeptide in a haemoglobin molecule that is different in sickle cell haemoglobin compared to normal haemoglobin.[1]
5. (d)Fig. 3.2 shows the oxygen dissociation curve for adult haemoglobin in a person who does not have sickle cell anaemia. [Figure 3.2] Compared to Fig. 3.2, the oxygen dissociation curve for adult haemoglobin in a person with sickle cell anaemia is shifted to the right. The uptake of oxygen by haemoglobin in the lungs and the release of oxygen by haemoglobin in respiring tissues is different in a person with sickle cell anaemia compared with a person who does not have the disease. With reference to Fig. 3.2, state and explain these differences. uptake of oxygen release of oxygen[3]

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