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1.7Biology 01. Structure And Function

Describe the components of blood and their functions — Cambridge Checkpoint Science 0893 Revision Notes & Topical Questions

5 min read 7 parts Lesson 7 of 12 1 quiz

📚 Cambridge Checkpoint Science 0893 Hub / Topical Revision
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Lesson summary

1.7 Blood and its Components — CHECKPOINT - Lower Secondary Science 0893 notes: Describe the components of blood and their functions.Respiration — every cell needs glucose and oxygen for respiration, and carbon dioxide and water made by the cell must be taken away.Blood — it deli…

  • Haemoglobin
  • No nucleus
  • No mitochondria
  • Small size
  • Phagocytosis
  • Antibodies

Part 1 of 5Why blood is needed

Respiration
  • Respiration every cell needs glucose and oxygen for respiration, and carbon dioxide and water made by the cell must be taken away.
Blood
  • Blood it delivers and removes these substances as it moves around the body in blood vessels pumped by the heart.

Part 2 of 5Components of blood

ComponentStructureFunction
PlasmaPale yellow liquid, mostly waterCarries blood cells and dissolved substances
Red blood cellsBiconcave discs with no nucleus and no mitochondriaCarry oxygen using haemoglobin
White blood cellsHave a nucleus, some are larger than red cellsDefend against pathogens
PlateletsCell fragmentsHelp blood to clot

Part 3 of 5Plasma

Plasma
Plasma the liquid part of the blood, mostly water, in which blood cells float.
Glucose
  • Glucose it dissolves in plasma and is transported from the digestive system to every cell.
Carbon dioxide
  • Carbon dioxide it dissolves in plasma and is carried to the lungs, where it diffuses out and is breathed out.

Part 4 of 5Red blood cells

Number
  • Number most blood cells are red, with about five million in every cm³ of blood.
Haemoglobin
  • Haemoglobin a red pigment in the cytoplasm that carries oxygen and makes blood look red.
No nucleus
  • No nucleus this leaves more space for haemoglobin.
No mitochondria
  • No mitochondria this stops the cells using up the oxygen they carry.
Small size
  • Small size it lets them squeeze through tiny capillaries close to the alveoli and respiring cells.
1
In the lung capillaries oxygen diffuses from the alveoli into red blood cells.
2
Oxygen combines with haemoglobin to form bright red oxyhaemoglobin.
3
Near respiring cells oxyhaemoglobin releases its oxygen, which diffuses into the cells.
4
The blood returns to the lungs to collect more oxygen.

Part 5 of 5White blood cells

White blood cells
Structure
  • Structure they always have a nucleus, and some kinds are larger than red blood cells.
Pathogens
  • Pathogens bacteria and viruses that cause illness are pathogens, and white blood cells help defend the body against them.
Phagocytosis
  • Phagocytosis some white blood cells push out their cytoplasm to capture a bacterium, then make chemicals that kill and digest it.
Antibodies
  • Antibodies other white blood cells make chemicals called antibodies that stick to a pathogen.
  • Each kind of pathogen needs a different kind of antibody.
  • Antibodies sometimes kill the pathogen directly, or glue pathogens together so other white blood cells can capture and kill them.

Key terms

TermMeaning
PlasmaThe liquid part of blood.
Red blood cellA cell with no nucleus, full of haemoglobin, that carries oxygen.
White blood cellA blood cell with a nucleus that defends against pathogens.
HaemoglobinRed pigment that carries oxygen.
PlateletA cell fragment that helps blood to clot.
AntibodyA chemical made by white blood cells that sticks to a pathogen.
PhagocytosisCapturing and digesting a pathogen by a white blood cell.
PathogenA microorganism that causes disease.

Avoid these mistakes

1
Saying plasma is red — plasma is a very pale yellow liquid, and red blood cells make blood look red.
2
Saying red blood cells have a nucleus — they have none, whereas white blood cells always do.
3
Saying blood carries only oxygen — it also carries glucose, carbon dioxide and other dissolved substances.
4
Confusing phagocytosis with antibody action — phagocytosis is capture and digestion, and antibodies stick to pathogens.

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