How Polar Bears Maintain Their Body Temperature: The Importance of Uncoupling Proteins

Polar bears are perfectly adapted to survive in the icy, frigid environment of the Arctic. To maintain their core body temperature despite extreme cold, they rely on a combination of physical and physiological adaptations. Among these, the presence of specialized proteins plays a critical role.

Understanding the Options

To maintain body temperature, organisms use different mechanisms. The question asks which protein polar bears have more of to help with thermoregulation:

1. Transducin protein — Primarily involved in visual signal transduction in the retina, unrelated to thermoregulation.

2. Uncoupling protein — Found in mitochondria, uncoupling proteins play an essential role in heat production by generating heat instead of ATP through a process called non-shivering thermogenesis.

3. Myoglobin protein — Oxygen-storing protein found in muscle cells, important for oxygen storage during diving but not directly linked to thermoregulation.

4. FOF1 ATPase — An enzyme complex involved in ATP synthesis during cellular respiration, not specifically related to generating body heat.

Why Uncoupling Protein Is Key

Polar bears possess higher levels of uncoupling proteins (UCPs), especially in brown adipose tissue. These proteins allow mitochondria to produce heat by “uncoupling” oxidative phosphorylation, meaning the energy from food metabolism is released as heat rather than stored as ATP.

This process, termed non-shivering thermogenesis, is vital for generating warmth without muscle activity and helps polar bears maintain their internal temperatures in the Arctic’s freezing environment.

Other Physiological Adaptations

Besides uncoupling proteins, polar bears have:

• A thick layer of insulating fat (blubber)

• Dense fur with water-repellent properties

• Specialized circulatory adaptations to conserve heat

However, only uncoupling proteins directly generate heat metabolically at the cellular level.

Conclusion

The main protein polar bears have more of to maintain body temperature is the uncoupling protein. It enables them to generate metabolic heat efficiently in extreme cold environments.

Therefore, the correct answer is:
(2) Uncoupling protein.