Non-shivering thermogenesis is mediated bya) α1 receptorb) β2 receptorc) β3 receptord) UCP-2e) UCP-1

**Core Concept**
Non-shivering thermogenesis is a process by which the body generates heat without muscle movement, primarily in brown adipose tissue (BAT). This process is crucial for regulating body temperature, especially in infants and small mammals.

**Why the Correct Answer is Right**
The correct answer is mediated by the uncoupling protein 1 (UCP-1). UCP-1 is a mitochondrial protein found in brown adipose tissue, which allows for the uncoupling of oxidative phosphorylation from ATP synthesis, resulting in the generation of heat instead of ATP. This process is essential for non-shivering thermogenesis, allowing the body to maintain a stable temperature in cold environments.

**Why Each Wrong Option is Incorrect**
**Option A:** α1 receptor is involved in smooth muscle contraction and has no direct role in thermogenesis.
**Option B:** β2 receptor is primarily involved in bronchodilation and vasodilation, but not in thermogenesis.
**Option C:** β3 receptor is involved in lipolysis and glucose metabolism, but not specifically in non-shivering thermogenesis.
**Option D:** UCP-2 is involved in mitochondrial uncoupling, but it is not the primary protein responsible for non-shivering thermogenesis.

**Clinical Pearl / High-Yield Fact**
Brown adipose tissue (BAT) is highly metabolically active and is a key player in non-shivering thermogenesis. It is most active in infants and small mammals, but it is also present in adults, particularly in the neck and supraclavicular regions.

**Correct Answer: E. UCP-1**