Final answer:
The body can produce 12 out of the 20 amino acids used in protein synthesis for hair, with the remaining 9 being essential and needing to be obtained through diet.
Step-by-step explanation:
The human body utilizes 20 different amino acids to synthesize proteins, such as those found in hair. While the body can synthesize 12 of these amino acids, there are 9 essential amino acids that it cannot produce and thus must be obtained through diet. Hair, being made of protein, relies on these amino acids for its structure and strength. Especially for infants and children who are still growing, it is crucial to consume a diet with the necessary amino acids as their bodies have a greater demand for them to support growth.
There are also two additional amino acids found in limited quantities in proteins, known as selenocysteine and pyrrolysine. The need for dietary protein (containing essential amino acids) is underscored by the fact that, unlike fats and carbohydrates, the body does not store excess amino acids, requiring a daily intake to meet its needs.
In summary, to make up hair, the body can produce more than 10 amino acids, but it requires obtaining the rest from dietary sources to ensure proper hair growth and maintenance.