AQA Biology 4.2.2.3
Blood
Blood is a tissue: a liquid with cells and cell fragments floating in it. Learn to tell them apart on sight, and what each one does.
Combined Science · Foundation tier
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A graze on your knee.
You graze your knee. It bleeds for a minute, then the bleeding stops, and by the next day there is a scab.
If you had to guess, is the bleeding stopped by whole cells, or by tiny bits of cells?
A blood smear · name what you see
Pick a labelled cell. Name it, then give its job.
0 of 4 named and matched
What is cell A?
Four components · structure and job
Plasma carries; the cells do the rest.
Red blood cells
Carry oxygen from the lungs to the tissues. Haemoglobin binds oxygen in the lungs and releases it in the tissues.
- Biconcave shape: a large surface area for oxygen to diffuse in and out.
- No nucleus: more room for haemoglobin.
- Packed with haemoglobin.
White blood cells
Larger than red cells, and each has a nucleus. They defend against pathogens in three ways:
- Phagocytosis: phagocytes engulf pathogens and digest them.
- Antibody production: lymphocytes make antibodies that target a particular pathogen.
- Antitoxin production: antitoxins neutralise the toxins released by bacteria.
Platelets
Small fragments of cells, with no nucleus. They help the blood to clot at a wound, which stops bleeding and keeps pathogens out.
Plasma
The pale yellow liquid the cells are carried in. It transports dissolved glucose and amino acids, carbon dioxide, urea, hormones and antibodies.
Think again · white blood cells
“All white blood cells fight germs by eating them.”
Your call
ChooseSome bacteria release toxins that make you ill. What do some white blood cells make to deal with the toxins?
Sort
Which component?
Place each description with the part of the blood it describes.
Tap a card, then tap the box it belongs in. Tap a placed card to take it back.
Command words in this lesson
- Identify
- Name the cell from what you can see: size, shape, nucleus or not.
- Describe
- Say what each component does.
- Explain
- Feature, then what it does for the job: no nucleus, so more room for haemoglobin.
Key fact
Blood is a tissue of plasma, with red blood cells, white blood cells and platelets suspended in it. Red cells carry oxygen, white cells defend against pathogens, platelets help clotting, and plasma transports dissolved substances.
Key note · AQA 4.2.2.3
Blood
- Blood is a tissue: plasma, with red blood cells, white blood cells and platelets suspended in it.
- Red blood cells carry oxygen: haemoglobin, no nucleus (more room for haemoglobin), biconcave (large surface area).
- White blood cells have a nucleus: phagocytosis, antibody production, antitoxin production.
- Platelets: small fragments of cells, no nucleus; help the blood to clot.
- Plasma: transports dissolved glucose, amino acids, carbon dioxide, urea, hormones and antibodies.
- Recognise them: red = small pale-centred discs; white = larger with a nucleus; platelets = tiny fragments.
Photograph this card. Tomorrow, cover it and say each line first.
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Ask MrBadmus
Mixing up phagocytes and lymphocytes?
The smear is a drawing in the style of a stained micrograph, not a photograph. Cells are not to scale with each other.