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Figure 6 shows the structure and actual size of red blood cells (erythrocytes) - Edexcel - GCSE Biology Combined Science - Question 3 - 2021 - Paper 1
Question 3
Figure 6 shows the structure and actual size of red blood cells (erythrocytes). Figure 6 (a) (i) Calculate the image size of the top view of this red blood cell if... show full transcript
Worked Solution & Example Answer:Figure 6 shows the structure and actual size of red blood cells (erythrocytes) - Edexcel - GCSE Biology Combined Science - Question 3 - 2021 - Paper 1
Step 1
Calculate the image size of the top view of this red blood cell if this cell is magnified 400×.
Answer
To find the image size of the red blood cell when magnified, use the formula:
Given that the actual size of the top view of the red blood cell is 7.5 μm and the magnification is 400:
Now convert micrometers to millimeters:
3000 ext{ μm} = rac{3000}{1000} = 3 ext{ mm}Step 2
Explain how the shape of a red blood cell is related to its function.
Answer
The shape of a red blood cell is typically that of a biconcave disc, which provides several advantages for its function:
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Increased Surface Area: The biconcave shape increases the surface area to volume ratio, allowing for greater efficient gas exchange (oxygen and carbon dioxide) with surrounding tissues.
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Flexibility: This shape allows red blood cells to be flexible and deformable, enabling them to squeeze through narrow capillaries and reach tissues effectively.
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Optimal Hemoglobin Positioning: The center of the cell is thin, facilitating the positioning of hemoglobin, which is crucial for oxygen binding and transport.
Overall, these structural adaptations enhance the red blood cell's primary function of transporting oxygen and carbon dioxide throughout the body.
Step 3
State the role of haemoglobin inside the red blood cell.
Answer
The role of haemoglobin inside the red blood cell is to transport oxygen from the lungs to the tissues and organs and to facilitate the return of carbon dioxide from the tissues back to the lungs for exhalation. Haemoglobin achieves this by binding reversibly to oxygen molecules, allowing efficient delivery and uptake.
Step 4
Explain why red blood cells cannot be stored in pure water.
Answer
Red blood cells cannot be stored in pure water due to the principle of osmosis. If red blood cells are placed in pure water, water would enter the cells by osmosis, causing them to swell and potentially burst (hemolysis). To maintain the integrity of red blood cells, they need to be stored in isotonic solutions, such as those containing 0.9% salt, which ensures that there is no net movement of water into or out of the cells, preserving their shape and function.