Match the following polysaccharides with their correct functions: Energy reserve - _____.

The correct match for "Energy reserve" is starch. Starch serves as a vital carbohydrate storage molecule in plants, providing a form of energy that can be easily mobilized when required. It is composed of long chains of glucose units, allowing plants to store excess glucose produced through photosynthesis. When energy is needed, starch can be broken down into glucose molecules, facilitating a quick response to energy demands.

While other polysaccharides like glycogen also function as energy reserves, especially in animals, the question specifies a match with starch, which is primarily associated with energy storage in plant systems. This distinction highlights the different roles of polysaccharides in various organisms, where starch is predominantly employed by plants whereas glycogen serves similar purposes in animals. Therefore, starch is the most appropriate answer for the function of an "Energy reserve."