What element makes protein different from carbohydrate and fat?
a. Carbon
b. Hydrogen
c. Oxygen
d. Nitrogen
The Correct Answer and Explanation is:
The correct answer is d. Nitrogen.
Proteins are unique among the three macronutrients (carbohydrates, fats, and proteins) because they contain nitrogen in addition to carbon, hydrogen, and oxygen, which are found in all three macronutrients. This key difference is what distinguishes proteins from carbohydrates and fats.
1. Structure of Macronutrients:
- Carbohydrates are composed of carbon, hydrogen, and oxygen. Their basic building blocks are monosaccharides like glucose, which are primarily used by the body for energy.
- Fats (lipids) are made of carbon, hydrogen, and oxygen, with a structure typically consisting of fatty acids and glycerol. Fats are primarily used for energy storage, insulation, and cell membrane structure.
- Proteins, however, contain carbon, hydrogen, oxygen, and nitrogen. The nitrogen comes from the amino group (–NH2) present in amino acids, which are the building blocks of proteins.
2. Role of Nitrogen in Proteins:
- Nitrogen is a crucial component of amino acids, which are the foundational units of proteins. There are 20 different amino acids, each containing a unique side chain, but they all share the amino group (–NH2) containing nitrogen.
- This nitrogen-containing structure is essential for the synthesis of proteins in the body. The presence of nitrogen allows the formation of peptide bonds between amino acids, resulting in long chains that fold into functional proteins.
- Proteins serve a wide range of roles in the body, including structural functions (like collagen and keratin), enzymatic functions (as enzymes), immune responses (antibodies), and many others.
3. Metabolism and Excretion:
- The presence of nitrogen also influences how the body handles proteins. When proteins are broken down for energy or to build new proteins, the nitrogen in the amino acids is removed through a process called deamination, and the waste product, urea, is excreted in the urine. This is not necessary for carbohydrates and fats, which do not contain nitrogen.
Thus, nitrogen is the distinguishing element that makes proteins different from carbohydrates and fats.