Fig. 1 shows a close-up of a red blood cell moving through a narrow capillary. The cell is drawn as a biconcave disc. Its shape gives a large surface area c...
Question 1 Report
Fig. 1 shows a close-up of a red blood cell moving through a narrow capillary. The cell is drawn as a biconcave disc. Its shape gives a large surface area compared with a spherical cell of the same volume. Haemoglobin inside the cell combines with oxygen in the lungs and releases oxygen near respiring body cells.
(a) Describe the shape of the red blood cell. [1]
(b) Give one advantage of this shape for oxygen transport. [1]
(c) What is the name of the pigment that carries oxygen in red blood cells? [1]
A technician prepared blood smears from a healthy donor and viewed them using a microscope. The donor had recently recovered from a bacterial infection. The technician identified red blood cells, white blood cells and platelets in several fields of view. The cells were suspended in plasma, which also carries dissolved substances such as glucose, carbon dioxide and urea around the body.
(a) Describe one visible difference between a red blood cell and a white blood cell. [1]
(b) Give the function of platelets after a cut to the skin. [1]
(c) Explain why red blood cells have no nucleus. [2]
(d) What substance in plasma transports most carbon dioxide from body cells to the lungs? [1]
Answer Details
Red blood cells
- A red blood cell is a biconcave disc, meaning a disc with a depressed centre. [1]
- This shape gives a large surface area, allowing rapid diffusion of oxygen. [1]
- The oxygen-carrying pigment is haemoglobin. [1]
Blood components
- A visible difference is that a red blood cell has no nucleus, whereas a white blood cell has a nucleus. [1]
- Platelets help the blood to clot after a cut. [1]
- Red blood cells have no nucleus, leaving more space for haemoglobin. More haemoglobin means that more oxygen can be carried. [2]
- Most carbon dioxide is transported in the plasma, mainly as dissolved bicarbonate ions. [1]
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