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

Where are functional proteins like testosterone found in the body?

1. In the pancreas

2. In the testes

3. In the heart

4. In the liver

The correct answer is: In the testes

Functional proteins like testosterone are primarily found in the testes, which are the male reproductive organs responsible for the production of sperm and hormones. Testosterone is a steroid hormone that plays a crucial role in the development of male reproductive tissues, the promotion of secondary sexual characteristics, and the regulation of various physiological functions. In the testes, Leydig cells specifically produce testosterone in response to stimulation from luteinizing hormone (LH). This hormone is essential not only for the maturation of sperm but also for influencing behaviors and physical attributes associated with male characteristics, such as increased muscle mass and bone density. The other options, while they do have important roles in the body, are not the primary sites for the production of testosterone. The pancreas is involved in digestion and blood sugar regulation, the heart is responsible for pumping blood, and the liver plays a key role in metabolism and toxin removal, none of which produce testosterone.