Question

What substance do cells use for energy? What type of food provides this?

Answer 1

Glucose breaks down into `"CO"_2` annd `"H"_2"O"` in cellular respiration to liberate energy in the form of ATP molecules which cells use for its metabolic and other activities.

Explanation:

Cells use energy liberated in cellular respiration in form of ATP molecules. Glucose (`bb("C"_6"H"_12"O"_6)`) acts as respiratory substrate. Cellular respiration is mainly aerobic that occurs in presence of `bb("O"_2)`.

Glucose is formed by the breakdown of starch in plants. Food is stored in the form of starch, a polysaccharide, in plants. Starch is made of thousands of units of glucose. Starch is hydrolyzed into glucose in a series of steps, controlled by hydrolyzing enzymes.

In animals, glucose is produced during digestion of carbohydrates present in their food . Glucose is carried to all cells in the body to be used in cellular respiration. Extra glucose is converted into glycogen and stored in liver. When enough glucose is not present in blood , Glycogen is converted into glucose in the presence of insulin hormone.