Biology 9700 · AS & A Level · Transport of oxygen and carbon dioxide

Transport of oxygen and carbon dioxide — practice question

Haemoglobin is a large, complex protein made up of four separate subunits, as shown in Fig. 3.1.
(a(i))[1]

The shading shows the two different polypeptides that make up a haemoglobin molecule. State the names of the two different polypeptides.

(a(ii))[1]

Identify which structure is labelled P in Fig. 3.1.

(a(iii))[1]

Fig. 3.1 presents some levels of protein structure. State the level of protein structure that is missing from Fig. 3.1.

(b)[3]

Haemoglobin helps transport carbon dioxide. As blood cells move through capillaries in muscle tissue, carbon dioxide molecules enter the red blood cells. Some of these molecules are converted into carbonic acid. Explain how haemoglobin is involved in transporting the carbon dioxide molecules that are not converted into carbonic acid.

(c)[1]

When haemoglobin attaches to oxygen, oxyhaemoglobin is formed. State the exact site in the mammalian body where haemoglobin molecules attach to oxygen.

(d(i))[2]

Use the information in Fig. 3.2 to describe the effect that an increased concentration of 2,3-DPG has on the oxygen dissociation curve.

(d(ii))[2]

Blood is kept in blood banks so it can be used in hospitals during operations. The concentration of 2,3-DPG in red blood cells falls while blood is stored in a blood bank. State and explain the effect that using blood taken from a blood bank has on the supply of oxygen to the tissues of a person during an operation.

Worked solution & mark scheme

This 11-mark question has a full step-by-step worked solution and mark scheme. One marking point: The alpha ($\alpha$) globin polypeptide chain and the beta ($\beta$) globin polypeptide chain.

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