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First exams 2025

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Cells of the Blood (CIE AS Biology)

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Cells of the Blood

  • Blood is a tissue composed of a number of important specialised cells
  • Red blood cells, monocytes, neutrophils and lymphocytes all have distinguishable structures which enable them to be recognised on microscope slides, in photomicrographs and in electron micrographs

Red blood cell diagram

Red Blood Cell

Diagram of the structure of a red blood cell

  • There are approximately 5 million red blood cells per mm3 of blood
  • Red blood cells contain haemoglobin, a protein with a quaternary structure that contains haem iron groups which can bind reversibly to oxygen
  • Distinctive features of erythrocytes when viewed under a microscope, are their distinctive biconcave disc shape (caused by their lack of nucleus)

A diagram of a micrograph of some red blood cells

Red Blood Cell Micrograph

Red blood cell micrograph

Diagram of a monocyte

Monocyte

A monocyte is a type of white blood cell

  • Monocytes are identifiable by their size – they are the largest of the leukocytes and have a nucleus shaped like a kidney or a bean
  • The nucleus of monocytes tends to appear lighter after staining than other leukocytes
  • The nucleus should appear a light blue colour, while the chromatin inside is distinct and fine

Monocyte micrograph diagram

Monocyte Micrograph

A micrograph of a monocyte cell

Neutrophil diagram

Neutrophil

A neutrophil is a type of white blood cell

  • Neutrophils are distinguished by their multi-lobed nuclei
  • Up to 70% of all leukocytes are neutrophils – this makes them easy to spot on a micrograph
  • The granules of neutrophils typically stain pink or purple-blue

Neutrophil micrograph diagram

Neutrophil Micrograph

A micrograph of a neutrophil cell

Lymphocyte diagram

Lymphocyte

A lymphocyte is a type of white blood cell

  • Lymphocytes are small leukocytes that are identifiable by their very large nuclei, which typically stains a dark colour
  • Lymphocytes constitute around 20-25% of all leukocytes
  • Lymphocytes are around the size of red blood cells

Lymphocyte micrograph diagram

Neutrophil Micrograph

A micrograph of some lymphocyte cells

Examiner Tip

When looking at micrographs, ensure you distinguish between the kidney-shaped nucleus of a monocyte and the multi-lobed nucleus of a neutrophil, as these can appear similar at first. As with all things, practice is key here!

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Emma

Author: Emma

Expertise: Biology

Prior to working at SME, Emma was a Biology teacher for 5 years. During those years she taught three different GCSE exam boards and two A-Level exam boards, gaining a wide range of teaching expertise in the subject. Emma particularly enjoys learning about ecology and conservation. Emma is passionate about making her students achieve the highest possible grades in their exams by creating amazing revision resources!