O-LevelBiologyTransport in Humans5090/21 · Oct/Nov 2023 · Q18 Marks

Human blood has many different components and functions. [Figure 1.1]

(a)Match each component to its function by drawing a line between them. One has been done for you.[3]
(b)(i)Explain how a red blood cell is specialised for transporting oxygen.[3]
(b)(ii)The number of red blood cells in 1 mm³ of blood is called a red blood cell count. A normal red blood cell count for a female is 4.2–5.4 million cells in 1 mm³ of blood. Suggest two factors that could lead to a change in the red blood cell count in a 25 year-old female.[2]

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Mark scheme

Marking points from the official mark scheme (Oct/Nov 2023). The mark or mark type is shown in brackets.

[3] 1(a) red blood cell -> transports oxygen (given); platelet -> involved in clotting; plasma -> transports fibrinogen; phagocyte -> engulfs pathogens; lymphocyte -> makes antibodies
[3] 1(b)(i) any three from: haemoglobin to bind with / carry / transport oxygen ; no nucleus so more room for haemoglobin ; small / flexible / elastic so can squeeze / fit along capillaries ; biconcave shape / large surface area for faster / rapid / more uptake / diffusion (of oxygen) ;
[2] 1(b)(ii) any two from: iron (in diet); anaemia / sickle cell anaemia; pregnancy; menstruation; accidental loss; altitude;

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