Question

How many carbon atoms are present in citric acid?
A. 8
B. 6
C. 10
D. 2

Answer 1

Citric acid is an organic acid that is formed from the citric acid cycle (Kreb’s cycle). The citric acid cycle is a part of glucose metabolism through which glucose is converted into pyruvate. In the cycle, Acetyl CoA combines with a four-carbon molecule and this leads to the production of citric acid.

Complete answer:
- 6 carbons are present in citric acid.
- Acetyl CoA is a two-carbon molecule that combines with oxaloacetate, which is a four-carbon molecule to form a six-carbon citric acid/citrate molecule.
- The citric acid cycle is a multi-step process and the production of citrate occurs in the first step itself.
- It is a weak organic acid that is colourless and odourless.
- In the human body, citric acid is found in almost all the cells, within the mitochondria. It is also found in many biological fluids such as urine, saliva, cerebrospinal fluid, and breast milk.
- Citric acid can also be found in a lot of food items such as oranges, lemons, raspberry, poppy opium, bamboo shoots, and many more. This means that it can act as a biomarker for these food items in our bodies.
- The presence of citric acid is also indicative of certain diseases and disorders like rhabdomyolysis, seizures, mental retardation, etc.

Hence, the correct answer is option (B).

Note: Citric acid can occur in two forms- in association with water (monohydrate) and free of water (anhydrous). The structure of citric acid is monoclinic crystalline. It has several domestic uses. Citric acid can be used as a cleaning agent, antioxidant, and even a preservative. It is added to food to give a sour taste.