Cambridge A Level Biology AS Bohr Shift Questions

[Maximum number: 4]

Fig. 5.1 is a longitudinal section of a capillary in muscle tissue as viewed with a transmission electron microscope.

Fig. 5.1

magnification $\times 2000$

Fig. 5.2 is a diagram showing some of the events that occur as blood flows through a capillary in a respiring tissue.

Fig. 5.2

An increase in respiration results in an increase in the carbon dioxide concentration in the blood and the release of more oxygen from red blood cells to tissues.

Explain how an increase in carbon dioxide in the blood leads to the release of more oxygen from red blood cells.

mark to max 3 if no ref. to 'more' at least once in the response

any four from:

1 more carbon dioxide diffuses into red blood cells ;

2 more carbonic acid is formed by carbonic anhydrase ;

3 formation of more hydrogen ions ; $\mathbf{A ~ H}^{+}$

4 haemoglobin has a high affinity for hydrogen ions ; $\mathbf{A ~ H}^{+}$

5 haemoglobin binds more hydrogen ions to form, haemoglobinic acid (HHb); $\mathbf{A} \mathrm{H}^{+}$

6 (formation of HHb) decreases affinity of haemoglobin for oxygen ;

7 haemoglobin releases more oxygen ;

8 carbon dioxide binds to $-\mathrm{NH}_{2}$ / N terminal, of, globin / polypeptides / $\alpha$ chains and $\beta$ chains ;

9 forms carbaminohaemoglobin ; R carboxyhaemoglobin also lowers affinity

10 allosteric effect / change in tertiary structure / AW, in (oxy)haemoglobin (causes, release / AW, more oxygen) ;

CAIE A-Level Biology AS 8.2.6 Bohr Shift and Its Importance Questions

Exam points

CAIE A-Level Biology AS 8.2.6 Bohr Shift and Its Importance Questions question 1