After you eat a protein bar, which chemical reactions introduced in this chapter must occur for the amino acids in the protein bar to be converted into proteins in your body cells?
The correct answer and explanation is:
After eating a protein bar, the amino acids in the bar must go through several chemical reactions before being incorporated into proteins in the body cells. These processes are primarily involved in digestion, absorption, and protein synthesis.
- Digestion: The first step occurs in the stomach and small intestine, where proteins in the protein bar are broken down into amino acids. This is done by enzymatic hydrolysis, a process where enzymes such as pepsin in the stomach and trypsin and chymotrypsin in the small intestine break the peptide bonds between amino acids. This results in the release of individual amino acids and smaller peptides.
- Absorption: Once the proteins are broken down into amino acids, they are absorbed by the enterocytes (cells lining the small intestine). These cells use transporters to move the amino acids into the bloodstream, where they are carried to various tissues, including muscle cells, liver, and others.
- Protein Synthesis: In the cells, the amino acids are used to build proteins through translation in the ribosomes. The sequence of amino acids is dictated by the mRNA (messenger RNA) that is transcribed from the DNA in the nucleus. This process involves tRNA (transfer RNA), which brings the appropriate amino acids to the ribosome, where they are linked together in the correct sequence to form a protein. This process requires energy in the form of ATP and involves various enzymes and co-factors.
- Post-Translation Modifications: After the protein is synthesized, it may undergo further modifications such as phosphorylation, glycosylation, or cleavage. These modifications help the protein achieve its final functional form.
In summary, the digestion of proteins into amino acids, their absorption into the bloodstream, and their incorporation into proteins through translation are key steps for the conversion of dietary amino acids into functional proteins in the body.