Question

REFLECT AND APPLY What are the sequences of all the possible tripeptides that contain the amino acids aspartic acid, leucine, and phenylalanine? Use the three-letter abbreviations to express your answer.

Short answer

Asp-Leu-Phe, Asp-Phe-Leu, Leu-Asp-Phe, Leu-Phe-Asp, Phe-Asp-Leu, Phe-Leu-Asp.

Step-by-step solution

- Identify amino acids and their abbreviations

First, identify the three amino acids given in the problem and their three-letter abbreviations. Aspartic Acid is abbreviated as Asp, Leucine as Leu, and Phenylalanine as Phe.

- Determine number of tripeptides

Calculate the number of possible tripeptide sequences. As there are 3 amino acids and each position in the tripeptide can be any of the 3 amino acids, there are a total of 3! (3 factorial) sequences possible.

- List all possible permutations

List all permutations of the three amino acids (Asp, Leu, and Phe). There are 6 permutations in total:

Step 3.1 - Permutation 1

Asp-Leu-Phe

Step 3.2 - Permutation 2

Asp-Phe-Leu

Step 3.3 - Permutation 3

Leu-Asp-Phe

Step 3.4 - Permutation 4

Leu-Phe-Asp

Step 3.5 - Permutation 5

Phe-Asp-Leu

Step 3.6 - Permutation 6

Phe-Leu-Asp

Key concepts

Amino Acids

Amino acids are the building blocks of proteins. Each amino acid has a specific structure that includes an amino group, a carboxyl group, a hydrogen atom, and a distinctive side chain or R group. The unique properties of the side chain determine the role of each amino acid in a protein.
There are 20 standard amino acids in nature. Each one plays a different role in protein folding and function. For example, aspartic acid (Asp) is typically found in the active sites of proteins because of its acidic properties.
Understanding amino acids is foundational to learning about biochemistry and molecular biology. They join together in specific sequences to form peptides and proteins, which perform countless functions in the body.

Permutations

Permutations refer to all the possible arrangements of a given set of elements. In this exercise, we are working with three amino acids: Aspartic Acid (Asp), Leucine (Leu), and Phenylalanine (Phe).
To find all possible tripeptide sequences, we calculate the permutations of these three amino acids. The formula for permutations of n elements is n!, which stands for 'n factorial.'
For three amino acids, we have 3!, which equals 3 x 2 x 1 = 6.
So, there are 6 different ways to arrange Asp, Leu, and Phe to form tripeptides:

• Permutation 1: Asp-Leu-Phe
• Permutation 2: Asp-Phe-Leu
• Permutation 3: Leu-Asp-Phe
• Permutation 4: Leu-Phe-Asp
• Permutation 5: Phe-Asp-Leu
• Permutation 6: Phe-Leu-Asp

Peptide Synthesis

Peptide synthesis is the process of creating peptides, which are short chains of amino acids. In biological systems, peptides are synthesized through a process called translation, which occurs in the ribosome. However, in a laboratory setting, peptides can be synthesized chemically.
Each amino acid in the chain is linked by a peptide bond, formed between the carboxyl group of one amino acid and the amino group of another. The sequence in which amino acids are linked is crucial, as it determines the peptide's properties and function.
In our exercise, we looked at the tripeptide sequence. Synthesizing tripeptides like Asp-Leu-Phe involves adding each amino acid step-by-step in a specific order to ensure the correct sequence.

Abbreviations of Amino Acids

Amino acids are commonly represented by both three-letter and single-letter abbreviations in scientific literature to save space and simplify communication.
In this exercise, we used three-letter abbreviations for Aspartic Acid (Asp), Leucine (Leu), and Phenylalanine (Phe). These abbreviations help quickly identify the amino acids involved without writing out their full names.
Knowing these abbreviations is essential for reading and understanding biochemical texts and databases, as well as for labeling and communicating sequences in peptide synthesis and protein studies.
Here are some examples of common amino acid abbreviations:

• Glycine - Gly (G)
• Alanine - Ala (A)
• Valine - Val (V)
• Tyrosine - Tyr (Y)
• Threonine - Thr (T)