GCSE Biology (AQA)

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Red Blood Cells

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Organisation Animal Tissues, Organs and Organ Systems

Red Blood Cells

1:37 Blood
Spec 4.2.2.3
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  • Red blood cells are crucial for transporting oxygen throughout the body.
  • There are about 5 billion red blood cells in a cubic centimeter of blood.
  • Red blood cells contain hemoglobin, which binds to oxygen from the alveoli.
  • Each red blood cell contains millions of hemoglobin molecules, giving them their red color.
  • Hemoglobin binds with oxygen to form oxyhemoglobin, which turns red blood cells bright red.
  • The color change in red blood cells is reversible as they deliver oxygen to tissues.
  • Blood always appears red, but can look blue through the skin due to the blood vessel walls; blue is also used in diagrams to represent deoxygenated blood.
  • Red blood cells are adapted for oxygen transport by lacking a nucleus, allowing more room for hemoglobin.
  • Their biconcave or disc shape provides a high surface area to volume ratio, maximizing oxygen diffusion.
  • Understanding how red blood cells are adapted to their function is a common exam question related to diffusion.

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