B3 1.7 Exchange in the gut

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The food you eat is broken down in your gut. Food molecules get turned into simple sugars, such as glucose, amino acids, fatty acids and glycerol. Your body cells need these products of digestion to provide fuel for respiration and the building blocks for growth and repair. A successful exchange surface is very important.

Absorption in the small intestine

For the digested food molecules to reach your cells they must move from inside your small intestine into your bloodstream. They do this by a combination of diffusion and active transport.

The diigested food molecules are small enough to pass freely through the walls of the small intestine into the blood vessels. They move in this direction because there is a very high concentration of food molecules in the gut and a much lower concentration in the blood. They move into the blood down a steep concentration gradient.

The lining of the small intestine is folded into thousands of tiny finger-like projections known


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