Question

Chemically, carbohydrate is:

• A. Acid
• B. Polyhydride or Aldehyde or Ketone
• C. Alcohol
• D. None Correct Answer: (B) Polyhydride or Aldehyde or Ketone

Hint:

To remember their composition, look closely at their open-chain forms: "Polyhydroxy" means they are rich in alcohol ($-OH$) groups, while "Aldehyde or Ketone" indicates the unique functional backbone that determines how they react as reducing or non-reducing sugars.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Carbohydrates are the most abundant biomolecules on Earth, acting as primary energy sources and structural components in living systems. Modern chemical definitions classify them based on their exact functional groups and atomic arrangements rather than just their empirical formula.

Step 2: Detailed Explanation:
Historically, carbohydrates were viewed simply as "hydrates of carbon" with the general formula $C_n(H_2O)_m$. However, structural chemical analyses revealed that they possess multiple hydroxyl ($-OH$) groups and a distinct carbonyl ($C=O$) functional group. Therefore, carbohydrates are strictly defined as optically active polyhydroxy aldehydes or polyhydroxy ketones, or larger molecular networks that break down into these simpler units upon hydrolysis.

• Aldoses: Carbohydrates containing an aldehyde group ($-CHO$) at the terminal position (e.g., Glucose).

• Ketoses: Carbohydrates containing a ketone group ($C=O$) at an internal position (e.g., Fructose).
In multiple-choice options, "Polyhydride" is commonly printed or adapted as a shorthand mistranslation/variant for "polyhydroxy" alongside their respective carbonyl groupings.

Step 3: Final Answer
Chemically, carbohydrates are classified as polyhydroxy (polyhydride) aldehydes or ketones.