OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What happens to excess amino acids in the body?

1. They are stored in the muscles

2. They are eliminated through urine

3. They are converted into fats and carbohydrates

4. They are transformed into new proteins

The correct answer is: They are converted into fats and carbohydrates

Excess amino acids play a specific role in metabolism because the body does not store them in the same way it stores fats and carbohydrates. When there is an extra supply of amino acids beyond what is needed for protein synthesis and other functions, the body undergoes a process called deamination. During this process, the amino group is removed from the amino acids, producing ammonia, which is then converted into urea for excretion in urine. The remaining carbon skeleton of the amino acids can be converted into various compounds, including fats and carbohydrates. This transformation allows the body to effectively utilize the surplus energy that might otherwise go to waste. The carbon skeletons can be used to generate glucose through gluconeogenesis or be converted into fatty acids for storage as triglycerides. This is essential for maintaining energy homeostasis and ensuring that any excess nutrients are not simply discarded, but rather repurposed to meet the body's energy needs. This metabolic flexibility highlights the body's adaptation to varying dietary conditions, ensuring that excess intake can still be used beneficially.