Question

(a) Draw the condensed structure of the tripeptide GlyGly-His. (b) How many different tripeptides can be made from the amino acids glycine and histidine? Give the abbreviations for each of these tripeptides, using the three-letter and one-letter codes for the amino acids.

Short answer

The condensed structure of the tripeptide GlyGly-His is: \(NH_2-CH_2-C-NH-CH_2-C-NH-CH(NH-CH=C-CH_2-NH)-COOH\). There are 8 different tripeptides that can be made from glycine (Gly, G) and histidine (His, H) as follows: 1. GlyGlyGly (GGG), 2. GlyGlyHis (GGH), 3. GlyHisGly (GHG), 4. GlyHisHis (GHH), 5. HisGlyGly (HGG), 6. HisGlyHis (HGH), 7. HisHisGly (HHG), and 8. HisHisHis (HHH).

Step-by-step solution

Understand the concept of tripeptides

Tripeptides are chains of three amino acids linked by peptide bonds. Amino acids combine through dehydration synthesis, which creates a covalent bond called a peptide bond between the amino group of one amino acid and the carboxyl group of another. The resulting compound is a dipeptide, and when three amino acids join in this way, they form a tripeptide. Glycine (Gly, G) and Histidine (His, H) are two different amino acids. In this exercise, we will draw the condensed structure for the tripeptide GlyGly-His and calculate how many different tripeptides can be made from these two amino acids.

Draw the condensed structure of the tripeptide GlyGly-His

To draw the condensed structure of a tripeptide, we need to connect the constituent amino acids through peptide bonds. For the tripeptide GlyGly-His, we should follow these steps: 1. Write the condensed structure of Glycine: \[NH_2-CH_2-COOH\] 2. Write the condensed structure of another Glycine: \[NH_2-CH_2-COOH\] 3. Write the condensed structure of Histidine: \[NH_2-CH(NH-CH=C-CH_2-NH)-COOH\] 4. Combine the amino acids with peptide bonds: - The first Glycine amino group (NH2) connects to the carboxyl group (COOH) of the second Glycine, forming a peptide bond (C-N). - The second Glycine amino group (NH2) connects to the carboxyl group (COOH) of the Histidine, forming another peptide bond (C-N). The final condensed structure for GlyGly-His is: \[NH_2-CH_2-C-NH-CH_2-C-NH-CH(NH-CH=C-CH_2-NH)-COOH\]

Calculate the number of different tripeptides that can be made from glycine and histidine

To calculate the number of different tripeptides that can be formed from glycine (G) and histidine (H), we need to consider that each position in the tripeptide can be filled with either glycine or histidine. There are 2 options for the first position, 2 options for the second position, and 2 options for the third position. Using the multiplication principle, the number of possible tripeptides is: 2 * 2 * 2 = 8 possible tripeptides

Write the abbreviations for each tripeptide using three-letter and one-letter codes

Now, we will list each of the possible tripeptides, along with their three-letter and one-letter codes: 1. GlyGlyGly (GGG) 2. GlyGlyHis (GGH) 3. GlyHisGly (GHG) 4. GlyHisHis (GHH) 5. HisGlyGly (HGG) 6. HisGlyHis (HGH) 7. HisHisGly (HHG) 8. HisHisHis (HHH) In conclusion, there are 8 different tripeptides that can be made from glycine (Gly, G) and histidine (His, H).

Key concepts

Peptide Bonds

Peptide bonds are like the stitches that tailor a protein's intricate structure. In biochemistry, these bonds are akin to superglue that fastens amino acids, the building blocks of proteins. When two amino acids join forces, their union is marked by the release of a water molecule—a process termed dehydration synthesis, leaving behind a sturdy covalent peptide bond.

Imagine one amino acid with an eager 'hand' (amine group, or -NH2) extending a bond to another amino acid's 'foot' (carboxyl group, or -COOH). Their handshake forms a peptide bond represented by -C-N-. This not only links two amino acids but also sets the stage for creating complex protein structures. When a specific number of amino acids join, we get a polypeptide, which evolves into a protein as it folds into a functional shape. Importantly, the peptide bond formation also influences the protein's final three-dimensional architecture.

Amino Acids

Amino acids are the alphabet of life's proteins, each with a unique side chain that gives it character and determines how it will connect with others in the protein story. There are twenty standard amino acids, and two of these superstars are glycine and histidine.

Glycine (Gly, G) is the simplest, with a single hydrogen atom as its side chain, while histidine (His, H) features an imidazole ring, adding a splash of complexity. These amino acids link up by shedding a water molecule to form peptide bonds. The diversity of proteins hinges on the various sequences and combinations of amino acids, each sequence creating a unique protein with a distinct role and function in the body. Glycine, for example, is lauded for its role in creating flexible protein areas, whereas histidine is critical for binding metal ions and acting as a proton donor or acceptor due to its aromatic ring with a nitrogen heteroatom.

Protein Structure

Protein structure is a marvelous tale of transformation, where a sequence of amino acids folds into a mesmerizing three-dimensional figure that's more than the sum of its parts. The structure of proteins can be dissected into four levels: primary, secondary, tertiary, and quaternary.

The primary structure is like the linear script of a play, with an exact sequence of amino acids. The secondary structure, consisting of alpha-helices and beta-pleated sheets, folds due to hydrogen bonding, much like the way a ribbon curls. The tertiary structure is the 3D shape of a single polypeptide chain, and quaternary structure is the complex of multiple folded polypeptide chains.

Understanding protein structure—including how tripeptides like GlyGly-His contribute to larger protein structures—is crucial in many scientific fields. Unlocking a protein's structure paves the way to comprehending its function and how it interfaces with various processes within living organisms. It is the blueprint that reveals the biomolecular world's secrets.