Lipids are different from other nutrient classes in that they
The Correct Answer and Explanation is:
Correct Answer:
Lipids are different from other nutrient classes in that they are not soluble in water.
Explanation
Lipids differ from other major nutrient classes — carbohydrates, proteins, vitamins, and minerals — primarily in their chemical structure and solubility. One of the most distinctive properties of lipids is that they are insoluble in water but soluble in organic solvents such as alcohol, ether, and chloroform. This makes them hydrophobic, meaning they do not mix with water. This characteristic sets lipids apart from carbohydrates and proteins, which are generally water-soluble.
Lipids include fats, oils, phospholipids, steroids, and waxes. They serve several critical functions in the body. First, lipids are a dense source of energy. Each gram of fat provides about 9 kilocalories, more than double the energy provided by carbohydrates and proteins, which each give about 4 kilocalories per gram. This makes lipids an efficient form of long-term energy storage.
Second, lipids are crucial for cell membrane structure, particularly phospholipids, which form the lipid bilayer that surrounds cells. This bilayer controls what enters and exits the cell, contributing to cellular integrity and communication.
Third, lipids help in the absorption of fat-soluble vitamins such as A, D, E, and K. Without lipids, the body would struggle to absorb these essential nutrients. Additionally, certain lipids like cholesterol serve as precursors for hormones such as estrogen and testosterone.
Lipids also provide thermal insulation and protection for internal organs. In cold environments, the fat stored beneath the skin helps conserve body heat. Around organs, fat acts as a cushion to protect them from mechanical shock.
In summary, lipids are distinct because they are water-insoluble, energy-dense, and play multiple vital roles in bodily functions. Their unique physical and chemical properties make them essential yet structurally and functionally different from other nutrients.
