Question

Write the amino acid sequences possible for a tripeptide containing the amino acids \(c y s,\) ala, and \(p h e,\) with each amino acid being used only once in each tripeptide.

Short answer

The 6 possible amino acid sequences for a tripeptide containing the amino acids Cys, Ala, and Phe, with each amino acid being used only once in each tripeptide, are: 1. Cys-Ala-Phe 2. Cys-Phe-Ala 3. Ala-Cys-Phe 4. Ala-Phe-Cys 5. Phe-Cys-Ala 6. Phe-Ala-Cys

Step-by-step solution

Identify the amino acids

We are given 3 amino acids: 1. Cys (cysteine) 2. Ala (alanine) 3. Phe (phenylalanine)

Find the total permutations

We need to arrange the 3 amino acids in a sequence. Each position can be filled by any one of the amino acids not already used. - Number of ways to fill the first position: 3 (cys, ala, or phe) - Number of ways to fill the second position: 2 (remaining two amino acids) - Number of ways to fill the third position: 1 (only one amino acid left) The total permutations can be calculated using the formula nPr = n!/(n-r)!, where n is the total number of objects, r is the number to be chosen, and n! is the factorial of n. In our case, n = 3 and r = 3, so the total permutations = 3!/(3-3)! = 3!/0! = 6.

List the possible tripeptide sequences

Since we know there are 6 possible tripeptide sequences, let's list them down: 1. Cys-Ala-Phe 2. Cys-Phe-Ala 3. Ala-Cys-Phe 4. Ala-Phe-Cys 5. Phe-Cys-Ala 6. Phe-Ala-Cys So, there are 6 possible amino acid sequences for a tripeptide containing the amino acids cys, ala, and phe, with each amino acid being used only once in each tripeptide.

Key concepts

Tripeptide

A tripeptide is a type of peptide that consists of three amino acids. These amino acids are linked together by peptide bonds. Each bond is formed when the carboxyl group of one amino acid reacts with the amino group of another, releasing a molecule of water. Tripeptides are important because they serve as the building blocks for proteins and play various roles in biological processes.

Tripeptides can vary greatly depending on the sequence of amino acids. The order in which the amino acids are arranged in the sequence can affect the tripeptide's properties and functions. For example:

• They may have different biological activity.
• They might show different stability and solubility.
• They can interact uniquely with biological receptors.

This variety is essential for the diverse functions that proteins perform in living organisms.

Cysteine

Cysteine is one of the amino acids that make up proteins and peptides, like tripeptides. It is unique because it contains a sulfur atom within its side chain. This sulfur atom plays a critical role in the formation of disulfide bonds.

Disulfide bonds are strong covalent bonds that help stabilize the three-dimensional structures of proteins. Here are some important points about cysteine:

• It can form disulfide bridges with other cysteine molecules.
• This contributes to the rigidity and stability of proteins.
• Cysteine is often found in enzymes and proteins that require stability.

Understanding cysteine's role can help us learn more about how protein structures are stabilized and how this affects their functions.

Alanine

Alanine is an aliphatic amino acid that is commonly found in proteins. It is characterized by its small, simple structure, consisting mainly of a methyl group as its side chain. Its simplicity offers several benefits when alanine is part of peptides or proteins.

Alanine is crucial due to its properties:

• It is often involved in protein structure, playing a role in stabilizing alpha-helices.
• Its small size helps in the compact folding of proteins.
• Alanine is sometimes used in scientific experiments to replace other amino acids and study changes in protein function.

Despite its simplicity, alanine is a vital component of protein stability and function.

Phenylalanine

Phenylalanine is an aromatic amino acid, notable for its larger size and a benzyl side chain. This distinct structure allows phenylalanine to play unique roles in proteins.

Some key functions and characteristics of phenylalanine include:

• It primarily contributes to protein interactions through stacking and hydrophobic environments.
• Phenylalanine residues can absorb ultraviolet light, aiding in the study of protein structure.
• As an essential amino acid, humans must obtain phenylalanine from their diet.

Phenylalanine's aromatic nature is crucial in protein interactions, making it an important focus in biochemistry and nutrition.