what are the building blocks of starch?
The correct answer and explanation is:
Correct Answer: The building blocks of starch are glucose molecules.
Starch is a carbohydrate and serves as the main energy storage polysaccharide in plants. Its basic unit is the simple sugar glucose, which is a monosaccharide. In plants, glucose is produced during photosynthesis. Once made, glucose can be linked together through chemical bonds to form large chains. These chains create the structure of starch. Starch is not just a single long chain of glucose; it is made of two types of molecules called amylose and amylopectin. Amylose is mostly a straight chain of glucose units linked together, while amylopectin is a branched chain with many side branches of glucose. This combination allows starch to be compact and store a lot of energy in a small space.
The bonds that hold glucose units together in starch are called glycosidic bonds. Specifically, amylose is made of glucose molecules linked mainly by alpha-1,4-glycosidic bonds. Amylopectin also has alpha-1,4-glycosidic bonds along the chain but includes alpha-1,6-glycosidic bonds at the branching points. This branched structure of amylopectin makes starch more easily broken down by enzymes when energy is needed.
Humans and animals cannot produce starch but consume it in their diet. When starch enters the body, enzymes such as amylase break it back down into individual glucose units. These glucose units are absorbed into the bloodstream and used by cells to produce energy through cellular respiration. Foods rich in starch include grains like rice and wheat, potatoes, corn and legumes. The energy stored in starch is vital for both plants and animals. In plants, starch can be broken down when the plant needs energy, especially when sunlight is not available for photosynthesis. Thus, glucose as the building block of starch is essential for energy storage and release in biological systems.