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Key points Source of information is based on textbooks & syllabus-specifications for students taking the AQA GCSE, Edexcel GCSE and OCR GCSE level biology examinations (~US grades 9-10).

Key points about the action of white blood cells in our immune system

Phagocytes, area a type of white blood cell, that form a key part of our non-specific immune response.

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Ingestion of Pathogens by Phagocytes – GCSE level Revision Notes

1. What Are Phagocytes?

• Phagocytes are a type of white blood cell (WBC).

• Part of the body’s non-specific immune response—they attack any foreign pathogen, not just a specific one.

• Their job is to engulf and digest invading microorganisms like bacteria and viruses.

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2. Steps in Phagocytosis (Ingestion of Pathogens)

1. Recognition and Attachment

   • The phagocyte detects chemicals on the surface of a pathogen or dead cell.

   • It moves towards the pathogen and binds to antigens on its surface.

2. Engulfment

   • The phagocyte surrounds the pathogen with its cell membrane, forming a vesicle called a phagosome.

3. Digestion

   • Lysosomes (organelles in the cytoplasm) fuse with the phagosome.

   • They release digestive enzymes that break down the pathogen.

4. Excretion

   • The broken-down components are either used by the cell or expelled as waste.

Mnemonic: R.E.D.E. – Recognise, Engulf, Digest, Expel

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3. What Happens Next?

• After digesting the pathogen, some phagocytes display pieces of it (antigens) on their surface.

• This helps activate specific immune responses, such as the production of antibodies by lymphocytes.

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Importance in Understanding Human Biology

For your understanding:

• Helps build a clear view of how the immune system keeps us safe.

• Demonstrates how even non-specific defences are complex and vital.

• Explains how vaccines and immune memory work in later stages.

For Exam Preparation:

• You may be asked to describe phagocytosis step-by-step.

• Could appear in labelled diagrams or compare phagocytes with lymphocytes.

• Useful in explaining how white blood cells help protect us from infection.

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Summary Table

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Learning objectives for this section on the action of white blood cells and phagocytes

Be able to describe, explain and understand the action of phagocyte white blood cells and their ingestion of pathogens - they destroy pathogen microorganisms like bacteria.

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