OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

Where in the body are dissolved food molecules absorbed from the digestive system?

1. Stomach

2. Large intestine

3. Small intestine

4. Pancreas

The correct answer is: Small intestine

Dissolved food molecules are primarily absorbed in the small intestine. This is because the small intestine has a large surface area due to the presence of villi and microvilli, which are tiny finger-like projections that increase absorption efficiency. The walls of the small intestine are also thin and lined with cells that facilitate the rapid transfer of nutrients into the bloodstream. Additionally, the small intestine is where most of the digestion occurs with the help of enzymes and bile, further breaking down food into its simplest forms — sugars, amino acids, fatty acids, and glycerol. These smaller molecules are then absorbed into the bloodstream through the walls of the small intestine, allowing them to be transported throughout the body to be used for energy, growth, and repair. The stomach primarily functions in the initial phase of digestion, breaking down food mechanically and chemically, but it does not absorb nutrients to the same extent as the small intestine. The large intestine is involved in the absorption of water and some salts, but it does not absorb food molecules. The pancreas plays a crucial role in digestion by producing enzymes and hormones but is not involved in the absorption process itself.