What type of molecule primarily provides energy storage in living organisms?

Polysaccharides are the primary molecules that provide energy storage in living organisms. These complex carbohydrates, which include structures such as starch and glycogen, can be broken down into simpler sugars like glucose, which serve as a vital energy source for cellular functions. The branching structure of polysaccharides allows for rapid access to glucose when energy is needed, making them efficient forms of energy storage.

In contrast, while proteins can also be used for energy, their primary role is to serve as building blocks for tissues and as enzymes facilitating biochemical reactions. Nucleic acids, such as DNA and RNA, are essential for genetic information storage and transmission but do not function directly in energy storage. Vitamins, on the other hand, are organic compounds that serve as co-factors in enzymatic reactions but are not involved in energy storage. Therefore, polysaccharides are uniquely suited for energy storage due to their structure and the way they are metabolized by the organism.