Carbon Percentage in the Human Body

The correct answer is option 'B' - 18 to 19 percent.

Explanation:
Carbon is one of the most abundant elements in the human body and plays a crucial role in the structure and function of biological molecules. It is a key component of organic compounds, including carbohydrates, lipids, proteins, and nucleic acids.

The percentage of carbon present in the human body varies depending on factors such as age, sex, and body composition. However, on average, carbon makes up approximately 18 to 19 percent of the total body mass.

Here is a breakdown of the carbon percentage in some of the major biomolecules found in the human body:

1. Carbohydrates:
- Carbohydrates are composed of carbon, hydrogen, and oxygen atoms.
- The general formula for carbohydrates is (CH2O)n, where "n" represents the number of carbon atoms.
- Carbon accounts for around 40 to 45 percent of the molecular weight of carbohydrates.

2. Lipids:
- Lipids, including fats, oils, and phospholipids, are composed of carbon, hydrogen, and oxygen atoms.
- Carbon contributes to approximately 70 to 75 percent of the molecular weight of lipids.

3. Proteins:
- Proteins are composed of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur atoms.
- Carbon accounts for about 50 percent of the molecular weight of proteins.

4. Nucleic Acids:
- Nucleic acids, such as DNA and RNA, are composed of carbon, hydrogen, oxygen, nitrogen, and phosphorus atoms.
- Carbon contributes to approximately 40 percent of the molecular weight of nucleic acids.

Considering the significant presence of carbon in these biomolecules, it is understandable that carbon makes up a substantial percentage of the human body's overall composition.

Therefore, the correct answer is option 'B' - 18 to 19 percent.