Yellowish structures that serve as an energy reserve are called

Lipids

Explanation:

Lipids are called energy reserves. Like carbohydrates, they can provide energy to the body but as readily as carbohydrates do. Lipids are also known as fats. Aside from providing the body with energy, they are also have a protective function. They act as cushions for different parts of the body like the heart. They are found in adipose tissue.

i believe it would be the lungs.

thats not a question