Blood
Revise Blood for GCSE Biology with this free worksheet and full mark scheme — Foundation and Higher exam-style questions with worked answers for AQA, Edexcel and OCR. Blood is a tissue made of four parts — red blood cells, white blood cells, platelets and plasma — each with a distinct role.
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These worksheets and mark schemes are original, written for Virtus Academy and checked against the current AQA, Edexcel and OCR specifications. Every worksheet comes with a full mark scheme.
Topic overview
Blood is a tissue consisting of a liquid called plasma with three types of component suspended in it: red blood cells, white blood cells and platelets.
Plasma transports dissolved substances including carbon dioxide, urea, glucose, hormones and heat. Red blood cells carry oxygen, white blood cells defend against pathogens, and platelets help the blood to clot.
Red blood cells are strikingly well adapted. They are biconcave discs, which gives a large surface area for absorbing oxygen; they contain haemoglobin, which binds oxygen; and they have no nucleus, which leaves more room for haemoglobin.
Revision notes
Plasma
Plasma is the straw-coloured liquid that carries the blood cells.
It transports carbon dioxide from the organs to the lungs, urea from the liver to the kidneys, and dissolved glucose, hormones, antibodies and heat around the body.
Red blood cells
Red blood cells carry oxygen from the lungs to respiring tissues.
Three adaptations: a biconcave disc shape giving a large surface area; haemoglobin which binds to oxygen forming oxyhaemoglobin; and no nucleus, leaving more space for haemoglobin.
White blood cells and platelets
White blood cells defend against pathogens — some engulf and digest them, some produce antibodies, and some produce antitoxins.
Platelets are cell fragments that help the blood clot at a wound, forming a scab that prevents blood loss and stops pathogens entering.
Key points
- Blood is a tissue made of plasma plus cells and platelets.
- Plasma transports carbon dioxide, urea, glucose and hormones.
- Red blood cells carry oxygen using haemoglobin.
- Red blood cells are biconcave and have no nucleus.
- White blood cells defend against pathogens.
- Platelets help the blood to clot.
Worked examples
Example 1
Describe two adaptations of a red blood cell and explain each. [4 marks]
Model answer
It is a biconcave disc, which gives a large surface area to volume ratio for absorbing oxygen quickly (2 marks). It has no nucleus, which leaves more room inside the cell for haemoglobin so it can carry more oxygen (2 marks).
Example 2
Name three substances transported by blood plasma. [3 marks]
Model answer
Carbon dioxide (1 mark), urea (1 mark) and dissolved glucose (1 mark).
Example 3
Explain why a person with a low red blood cell count may feel tired. [3 marks]
Model answer
Fewer red blood cells means less haemoglobin (1 mark), so less oxygen is transported to the body's cells (1 mark). Less oxygen means a lower rate of aerobic respiration, so less energy is released and the person feels tired (1 mark).
Common mistakes
Saying red blood cells carry carbon dioxide.
Most carbon dioxide is carried dissolved in the plasma.
Calling platelets cells.
They are cell fragments, not whole cells.
Saying red blood cells have no organelles at all.
The key point is that they have no nucleus, which makes room for haemoglobin.
Giving an adaptation without explaining its benefit.
Say the biconcave shape increases surface area for oxygen absorption.
Exam tips
- Always pair each red blood cell adaptation with its benefit.
- Remember plasma, not red cells, carries most carbon dioxide.
- Name haemoglobin explicitly when discussing oxygen transport.
- Link low oxygen to reduced respiration and less energy released.
Key terms
- Plasma
- The liquid part of blood that transports dissolved substances.
- Haemoglobin
- The protein in red blood cells that binds oxygen.
- Platelet
- A cell fragment that helps blood to clot.
- Biconcave
- Disc-shaped with both surfaces curved inwards.
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Written and reviewed against the current AQA, Edexcel and OCR specifications. Spotted an error? Let us know.