The Circulatory System (Edexcel International A Level Biology)

The role of haemoglobin is to transport oxygen and carbon dioxide in the blood.

The diagram shows the structure of adult haemoglobin

State the role of the structure labelled P.

(1)

(ii)

Explain the properties of amino acids located on the outer surface of the haemoglobin, for example at position Q.

(2)

The graph shows the oxygen dissociation curves of adult and fetal haemoglobin.

Explain why the oxygen dissociation curve of adult haemoglobin is different from that of fetal haemoglobin.

(2)

(iii)

The structures of adult and fetal haemoglobin are different.

The diagram shows the structure of adult and fetal haemoglobin.

The amino acids in the α chains are the same in adult and fetal haemoglobin.
The β and γ chains differ in 39 of their amino acids.

Calculate the percentage of amino acids that are different in adult and fetal haemoglobin.

(2)

Warfarin is a drug used to treat people who have a blood clot.

Read through the following passage about warfarin.

Write on the dotted lines the most appropriate word or words to complete the passage.

(3)

Warfarin is used to treat people with blood clots as it lowers the number of clotting factors in the blood.

One clotting factor in blood is prothrombin.

Prothrombin is converted to the enzyme thrombin by ..........................................

The ............................................ of thrombin binds to fibrinogen and as a result a mesh of fibres and ................................................. is formed.

(1)

The time taken for a blood sample to form a blood clot can be measured. This is called the clotting time.

The graph shows the blood clotting time after a patient has stopped taking warfarin.
Calculate the rate of decrease in the clotting time at two days after stopping taking warfarin.

Use a tangent for your calculation.

Stents are used in the treatment of atherosclerosis.

The diagram shows how stents are positioned in a diseased coronary artery.
Explain why a stent is used in the treatment of atherosclerosis in a coronary artery.

Inserting a stent can damage the artery.

This damage can result in stent thrombosis if the blood clotting process is stimulated.

A study looked at the damage caused by two different types of stent, stent A and stent B.

The graph shows the incidence of stent thrombosis found in this study.

In this study, 800 patients had stent A inserted and 400 patients had stent B inserted.

Calculate the difference in the number of patients who developed stent thrombosis three years after inserting the stent.

(2)

(ii)

State how the formation of a blood clot in the coronary artery could cause the death of the patient.

(1)

(iii)

Which components of the blood clotting process are enzymes in their active form?

(1)

Which components of the blood clotting process are soluble in blood plasma?

(1)

(v)

Stent B contains a drug to prevent stent thrombosis.

Suggest one type of drug that could be used in stent B.

(1)

Many animals have a heart and circulation.

The diagram shows the structure of a human heart.

Label the diagram with the names of the four major blood vessels.

The table shows some structures and the types of blood vessel that they are found in.

Put a cross ☒ in each row to show where these structures are found.

The graph shows the velocity of the blood as it flows through the arteries into the capillaries and then into the veins.

Describe the changes in the velocity of the blood as it flows from an artery to a vein.

The cardiac cycle describes the events that take place in the heart during one complete heartbeat.

The diagram shows a heart in one of the stages, stage F, of the cardiac cycle.

(1)

(1)

The graph shows pressure changes in the left ventricle of a person.

Calculate the heart rate of this person.

Express your answer to 3 significant figures.

(2)

Another line could be drawn on this graph to show the pressure changes in the right ventricle.

Describe the shape and position of this line.

Give reasons for your answer.

(3)

Warfarin is used in the treatment of cardiovascular disease.

Warfarin inhibits the synthesis of prothrombin.

Describe the role of prothrombin in the blood clotting process.

Which type of treatment is warfarin?

Reduced vitamin K is needed for the synthesis of prothrombin.

An enzyme, vitamin K epoxide reductase (VKOR), converts vitamin K to reduced vitamin K.

The diagram shows this conversion.

vitamin K  reduced vitamin K

(i)

The diagrams show the structures of warfarin and vitamin K.

Using the information in the diagrams, suggest why warfarin inhibits the synthesis of prothrombin.

(2)

(ii)

Suggest why people taking warfarin have to avoid eating foods that contain a high concentration of vitamin K.

(2)

Other drugs are available that work in a similar way to warfarin.

The diagram shows one study to compare the effect of warfarin with drug X.

Explain how this study should be designed so that the effectiveness of these two drugs can be compared.

Collagen is a component of the wall of the aorta.

(i)

Describe the structure of collagen.

(3)

Explain the role of collagen in the wall of the aorta.

(2)

Age and sex affect the types and density of collagen found in the wall of the aorta.

These are thought to cause aortic stiffness.

In one study, scientists investigated the effect of age and sex on aortic stiffness and the density of collagen in the wall of the aorta.

The graphs show the results of this study.


In another study, scientists investigated the effect of age and sex on two types of collagen present in the wall of the aorta.

The graphs show the relative proportion of each type of collagen in each group of monkeys.

Comment on the effect of age and sex on the types of collagen found in the wall of the aorta and aortic stiffness.

Use the information in the graphs to support your answer.