IGCSE · Practice questions · Blood

Four parts, four jobs.

Six original Cambridge-style questions on the components of blood, identifying cells, transport in plasma, defence by white blood cells and how blood clots.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.

Keep these straight

Match each part to its job.

Red blood cells: oxygen, using haemoglobin; no nucleus.
White blood cells: phagocytes engulf (lobed nucleus); lymphocytes make antibodies (large round nucleus).
Platelets: clotting; Extended: soluble fibrinogen to insoluble fibrin mesh.
Plasma: blood cells, ions, nutrients, urea, hormones, carbon dioxide.

Recall

[4 marks]

List the four components of blood and state one function of each.

Red blood cells: transport oxygen (using haemoglobin). ✓
White blood cells: phagocytosis or antibody production. ✓
Platelets: clotting. ✓
Plasma: transports blood cells, ions, nutrients, urea, hormones and carbon dioxide (any one). ✓

Explain

[3 marks]

Explain how red blood cells transport oxygen from the lungs to respiring tissues.

Red blood cells contain haemoglobin. ✓
In the lungs, where there is a lot of oxygen, haemoglobin combines with oxygen. ✓
In respiring tissues, where there is little oxygen, the haemoglobin releases the oxygen, which diffuses into the cells. ✓

Recall

[3 marks]

Name three substances, other than blood cells, carried by plasma, and for each state where it is carried from or to.

Glucose (nutrients): from the small intestine to all cells. ✓
Urea: from the liver to the kidneys. ✓
Carbon dioxide: from respiring cells to the lungs. (Also accept hormones from glands to target organs, or ions.) ✓

Analysis

[4 marks]

Extended. A student looks at a stained blood smear. Describe how she could distinguish (a) red blood cells from white blood cells, and (b) phagocytes from lymphocytes, and state the function of each type of white blood cell.

(a) Red blood cells have no nucleus (and are smaller, more numerous biconcave discs); white blood cells have a nucleus. ✓
(b) Phagocytes have a lobed nucleus; lymphocytes have a large, round nucleus that fills most of the cell. ✓
Phagocytes engulf pathogens by phagocytosis. ✓
Lymphocytes produce antibodies. ✓

Explain

[4 marks]

Extended. Describe the process of blood clotting and explain why it is important.

At a wound, platelets help trigger clotting. ✓
The soluble plasma protein fibrinogen is converted into insoluble fibrin. ✓
Fibrin forms a mesh of threads that traps red blood cells, forming a clot (which dries into a scab). ✓
The clot prevents blood loss and prevents pathogens entering the body through the wound. ✓

Data

[3 marks]

A blood test gives the following counts for a patient.

Component	Patient / per mm³	Normal range / per mm³
red blood cells	3 200 000	4 500 000 to 5 500 000
white blood cells	7 000	4 000 to 11 000
platelets	260 000	150 000 to 400 000

(a) Which count is outside the normal range? (b) Suggest one symptom the patient may have and explain it.

(a) The red blood cell count is below the normal range. ✓
(b) Tiredness, lack of energy or breathlessness. ✓
Fewer red blood cells means less haemoglobin, so less oxygen is carried to the tissues and less energy is released by aerobic respiration. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.