Question

Glucose is broken down to 3-carbon compound called :

• A. Oxaloacetate
• B. Citrate
• C. Pyruvate
• D. Acetate

Hint:

The first major step in breaking down glucose for energy is {glycolysis}. In glycolysis: 1 Glucose molecule (which has 6 carbons) \(\downarrow\) 2 Pyruvate molecules (each has 3 carbons) This happens in the cytoplasm of the cell. Pyruvate is the key 3-carbon compound formed.

Answer 1

The Correct Option is C

Concept: The initial stage of cellular respiration, common to both aerobic and anaerobic respiration, is glycolysis. In this process, a glucose molecule is broken down. Step 1: Understanding Glycolysis Glycolysis is a metabolic pathway that occurs in the cytoplasm of cells. It involves a series of enzymatic reactions that convert one molecule of glucose (a 6-carbon sugar) into two molecules of a 3-carbon compound. This process also produces a net gain of ATP (energy currency) and NADH (an electron carrier). Step 2: The Product of Glycolysis The 6-carbon glucose molecule (\(C_6H_{12}O_6\)) is split and oxidized during glycolysis to form two molecules of pyruvate (also known as pyruvic acid). Pyruvate is a 3-carbon compound with the chemical formula \(CH_3COCOO^-\) (for the ion) or \(CH_3COCOOH\) (for the acid). Step 3: Analyzing the options
(1) Oxaloacetate: This is a 4-carbon molecule that is an intermediate in the Citric Acid Cycle (Krebs cycle).
(2) Citrate: This is a 6-carbon molecule that is formed in the first step of the Citric Acid Cycle when acetyl-CoA combines with oxaloacetate.
(3) Pyruvate: Correct. Glucose (6-carbon) is broken down into two molecules of pyruvate (3-carbon each) during glycolysis.
(4) Acetate: This is a 2-carbon molecule (often as acetyl-CoA, which is formed from pyruvate before entering the Citric Acid Cycle in aerobic respiration). Therefore, glucose is broken down to the 3-carbon compound called pyruvate.