GCSE Combined Science (AQA)

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Diffusion in the Intestines

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Cell Biology Transport in Cells

Diffusion in the Intestines

4:12 Diffusion in Action
Spec 4.1.3.1
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  • Diffusion is crucial for nutrient absorption during digestion.
  • The digestive system consists of various organs including the stomach, liver, and intestines.
  • Knowledge of the digestive system from key stage three science is assumed for GCSE biology.
  • Nutrients, such as glucose, are primarily absorbed in the small intestine.
  • The small intestine is depicted in the diagram with squiggly, darker pink lines, while the large intestine has a larger diameter and a straighter path.
  • The small intestine is adapted for nutrient absorption with structures called villi (singular: villus), which have a thin membrane and a large surface area to volume ratio.
  • Villi are lined with capillaries that facilitate molecule exchange and maintain a concentration gradient essential for diffusion.
  • Blood flow in the intestines helps maintain the concentration gradient by constantly moving, allowing nutrients to diffuse into the blood.
  • After a meal, glucose concentration is high in the lumen of the small intestine and diffuses into the blood due to the concentration gradient.
  • The absorbed glucose is then transported by the blood from the intestines to respiring tissues and organs throughout the body.

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