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

How does active transport function in the digestive system?

1. It allows the absorption of nutrients when in lower concentration

2. It prevents all nutrient absorption

3. It stimulates digestion by increasing nutrient concentration

4. It uses gravity to facilitate nutrient movement

The correct answer is: It allows the absorption of nutrients when in lower concentration

Active transport is a vital process in the digestive system that enables the absorption of nutrients against their concentration gradient. This means that even when nutrient concentrations are lower in the intestinal lumen compared to the cells lining the intestine, active transport mechanisms allow these nutrients to be absorbed. This process is essential for effectively taking up substances such as glucose and amino acids, which may not occur through passive diffusion due to their low concentration in the gut. Active transport requires energy, typically derived from ATP, which powers the movement of molecules through specific transport proteins in the cell membranes. In this way, active transport maximizes nutrient uptake, ensuring that the body can efficiently absorb the necessary components from the food consumed, even when they are present in lower concentrations inside the intestines. This capability significantly supports the nutritional needs of the body.