IGCSEBiologyCambridge (CIE)Revision Notes9. Transport in AnimalsCirculatory Systems, Heart & Blood VesselsComponents of Blood

Components of Blood (Cambridge (CIE) IGCSE Biology): Revision Note

Exam code: 0610 & 0970

Lára Marie McIvor

Written by: Lára Marie McIvor

Reviewed by: Jenna Quinn

Updated on

Cambridge (CIE) BiologyCambridge (CIE) Combined Science: Biology

Components of blood

  • Blood consists of red blood cells, white blood cells, platelets and plasma

Diagram of blood composition showing 55% plasma and 45% cells, composed of red blood cells, white blood cells and platelets
Composition of human blood

Components of the blood table

Component

Structure

Red blood cells

Biconcave discs with no nucleus, containing a large amount of the protein haemoglobin

White blood cells

Large cells with a large nucleus; different types (e.g. phagocytes and lymphocytes) have slightly different structures and functions

Platelets

Small fragments of cells, with no nucleus

Plasma

Pale yellow (straw-coloured) liquid, made mostly of water

Identifying red & white blood cells

  • Red and white blood cells can be identified in photomicrographs and diagrams by:

    • red blood cells have a concave disc shape with no nucleus

    • white blood cells are usually round in shape with a nucleus

Diagram of a micrograph showing many red blood cells, a few small platelets, and larger labelled white blood cells.
An illustration of a blood micrograph

Components of blood: function

  • Plasma is important for the transport of:

    • the blood cells (red blood cells, white blood cells and platelets)

    • nutrients

    • urea

    • ions

    • hormones

    • carbon dioxide

  • Red blood cells transport oxygen around the body from the lungs to cells around the body; oxygen is required for aerobic respiration

    • Red blood cells carry oxygen in the form of oxyhaemoglobin

  • White blood cells defend the body against infection by pathogens by carrying out phagocytosis and antibody production

  • Platelets are involved in blood clotting

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Author
Reviewer
Lára Marie McIvor

Author: Lára Marie McIvor

Expertise: Content Creator

Lára graduated from Oxford University in Biological Sciences and has now been a science tutor working in the UK for several years. Lára has a particular interest in the area of infectious disease and epidemiology, and enjoys creating original educational materials that develop confidence and facilitate learning.

Jenna Quinn

Reviewer: Jenna Quinn

Expertise: Content Creator

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.