Practise 30 exam-style questions on Blood for AQA GCSE Biology. Write your answer as you would in the exam and get it marked in seconds against the mark scheme, point by point, with an AI tutor on hand if you get stuck.
30 questions
2–4 marks each
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20 questions, marked as you go
Sample questions with model answers
Here are 4 of the questions in this topic, each with a model answer, an explanation of why it earns the marks and the mark scheme an examiner would use.
Question 1
2 marks
Explain why a haemoglobin molecule contains iron and what happens in iron deficiency anaemia.
Model answer
Iron is required in haemoglobin to bind oxygen (Fe in heme group); iron deficiency means less haemoglobin produced ? fewer RBCs or less oxygens carrying capacity ? tiredness and breathlessness.
Explanation
Iron in haemoglobin binds oxygen; without enough iron haemoglobin synthesis falls so oxygen transport capacity is reduced causing anaemia symptoms.
Mark scheme
1 mark
Iron (Fe) is part of haem group and binds oxygen
1 mark
Iron deficiency ? reduced haemoglobin / RBC oxygen carrying ? symptoms like tiredness
Question 2
3 marks
A patient needs a blood transfusion. Explain why it is important to match blood groups and the danger of an incompatible transfusion.
Model answer
If donor blood has antigens not present in recipient, recipient antibodies will bind and cause agglutination and haemolysis releasing cell contents causing kidney failure or shock. Matching prevents immune reaction.
Explanation
If blood groups are incompatible, recipient antibodies attack donor red cells causing clumping and destruction which can lead to organ damage and life-threatening reactions.
Mark scheme
1 mark
Donor antigens can be recognised as foreign by recipient antibodies
1 mark
Causes agglutination / haemolysis of donor RBCs
Allow mention of blockage, shock
1 mark
Can cause severe reactions (kidney failure, shock, death)
Award for clinical consequences
Question 3
3 marks
Explain why oedema (excess tissue fluid) can occur if plasma protein (albumin) levels fall.
Model answer
Plasma proteins help retain water in blood by oncotic pressure; if albumin falls plasma oncotic pressure decreases so more fluid leaves capillaries into tissues, causing oedema.
Explanation
Albumin maintains osmotic balance; reduced levels lower the blood's ability to hold water, so fluid accumulates in interstitial spaces producing swelling (oedema).
Mark scheme
1 mark
Plasma proteins (albumin) create oncotic pressure retaining water in capillaries
1 mark
Low albumin ? decreased oncotic pressure
1 mark
More fluid moves into tissues ? oedema
Question 4
4 marks
Design a simple practical method (outline) to observe red and white blood cells under a light microscope and how to prepare a stained blood smear.
Model answer
Place a drop of blood on slide, spread with another slide to make thin smear, allow to air dry, fix with methanol, stain with Wright/Giemsa/May-Grünwald (or similar), rinse and dry, view under oil immersion for RBC and WBC. Use safety: gloves, dispose in sharps/biohazard. Draw and label (if required).
Explanation
A blood smear is made by spreading a small drop across a slide, staining and examining under high power so RBCs (numerous, anucleate) and WBCs (larger, nucleated) can be distinguished; follow safety procedures.
Mark scheme
1 mark
Make thin smear with drop of blood spread across slide
1 mark
Allow to dry and stain with appropriate blood stain (Wright/Giemsa) and rinse/dry
1 mark
View under microscope (oil immersion for detail) to see RBC/WBC
1 mark
Mention of safety/sterility: gloves, dispose in biohazard/sharps
Award hygiene/safety point
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