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

Which of the following describes the role of kidney tubules?

1. They filter oxygen from the air

2. They remove excess glucose from the bloodstream

3. They are involved in water reabsorption

4. They synthesize hormones

The correct answer is: They are involved in water reabsorption

The primary function of kidney tubules is to facilitate water reabsorption, which is crucial for maintaining the body’s fluid balance. The kidney tubules, specifically within the nephron, play a vital role in processing the filtrate produced by the glomerulus. As this filtrate travels through the various segments of the tubules, including the proximal convoluted tubule, loop of Henle, and distal convoluted tubule, water is reabsorbed back into the bloodstream based on the body’s hydration needs. The reabsorption of water is regulated by hormones such as antidiuretic hormone (ADH), which increases the permeability of the tubules, allowing more water to be reabsorbed when the body is dehydrated. This process not only helps in concentrating urine but also aids in regulating blood pressure and overall fluid balance within the body. While other options mention processes that do occur in or are related to the kidneys, they do not accurately describe the primary role of kidney tubules. Thus, the focus on water reabsorption highlights the essential function of kidney tubules in maintaining homeostasis.