The chemical formula of starch is

A. (C₆H₁₀O₅)n

B. (C₆H₁₂O₆)n

C. C₁₂H₂₂O₁₁

D. CH₃COOH

To determine the correct chemical formula of starch, let's first understand what starch is and how it is structured. Starch is a polysaccharide, which means it is made up of many glucose units linked together. The options provided represent different chemical formulas, so we need to identify which one accurately reflects the structure of starch.

Analyzing the Options

• A. (C₆H₁₀O₅)n - This formula suggests a repeating unit of a carbohydrate, but it does not accurately represent starch.
• B. (C₆H₁₂O₆)n - This formula represents glucose, the monomer from which starch is made, but it does not account for the polymeric nature of starch.
• C. C₁₂H₂₂O₁₁ - This is the formula for sucrose, a disaccharide, not starch.
• D. CH₃COOH - This is the formula for acetic acid, which is unrelated to starch.

Identifying the Correct Formula

The correct answer is A. (C₆H₁₀O₅)n. This formula represents the repeating unit of amylose and amylopectin, the two components of starch. In starch, glucose molecules are linked together through glycosidic bonds, and the formula reflects the loss of water molecules during the formation of these bonds.

Understanding Starch Structure

Starch consists of two main components:

• Amylose
• Amylopectin: This is a branched structure with both α(1→4) and α(1→6) glycosidic bonds.

When glucose molecules polymerize to form starch, a condensation reaction occurs, where water is released. This is why the formula for starch is represented as (C₆H₁₀O₅)n, indicating that for every n glucose units, there are fewer hydrogen and oxygen atoms than in the free glucose molecule (C₆H₁₂O₆).

Conclusion

In summary, the chemical formula of starch is best represented by option A, (C₆H₁₀O₅)n. This reflects the polymeric nature of starch, derived from glucose units, and accounts for the water molecules lost during the formation of glycosidic bonds. Understanding this structure is crucial for grasping how starch functions as an energy storage molecule in plants.