Question

Proteins The average molecular weight of an amino acid residue in a polypeptide is 110. What is the approximate molecular weight of the following proteins? a. Insulin (51 amino acids) b. Myosin (1750 amino acids)

Short answer

The approximate molecular weights of Insulin and Myosin are 5610 and 192500, respectively.

Step-by-step solution

Calculate the molecular weight of Insulin

Using the formula mentioned above, we can calculate the approximate molecular weight of Insulin, which has 51 amino acids: Approximate Molecular Weight of Insulin = (51 amino acids) x (110)

Calculate the molecular weight of Myosin

Similarly, we can calculate the approximate molecular weight of Myosin, which has 1750 amino acids: Approximate Molecular Weight of Myosin = (1750 amino acids) x (110)

Evaluate the molecular weights of both proteins

Evaluate the results from step 1 and step 2 to determine the approximate molecular weights of Insulin and Myosin: Approximate Molecular Weight of Insulin = \(51 \times 110 = 5610\) Approximate Molecular Weight of Myosin = \(1750 \times 110 = 192500\) Hence, the approximate molecular weights of Insulin and Myosin are 5610 and 192500, respectively.

Key concepts

Amino Acids

At the heart of every protein are amino acids, the basic building blocks that link together to form polypeptides and ultimately the complex structures of proteins. There are 20 different amino acids in the body that play a vital role in constructing the enormous variety of proteins necessary for our biological functions.

Each amino acid has a central carbon atom, known as the alpha carbon, to which an amino group, a carboxyl group, a hydrogen atom, and a unique side chain called an 'R group' are attached. The chemical properties of the 'R group' determine the characteristics and function of the amino acid. Understanding the molecular structure of amino acids is fundamental in calculating the molecular weight of proteins, as exemplified in the given exercise, where the molecular weight of an amino acid residue is considered to be 110.

Polypeptide Chain

A polypeptide chain is a sequence of amino acids bound by peptide bonds, which are formed through a dehydration synthesis reaction between the amine group of one amino acid and the carboxyl group of another. This linear chain of amino acids folds in specific ways to create the three-dimensional structure of a protein.

The sequence of amino acids in a polypeptide determines the protein's properties and function. For example, insulin, with its 51 amino acids, is a hormone crucial for regulating glucose in the bloodstream, while myosin, a much larger protein with 1750 amino acids, is essential for muscle contraction.

Protein Structure

Protein structure is categorized into four levels: primary, secondary, tertiary, and quaternary structures. The primary structure is the linear sequence of amino acids in the polypeptide chain. Secondary structures refer to local arrangements of the polypeptide, such as the alpha helix and beta-pleated sheet, stabilized by hydrogen bonding. Tertiary structure denotes the complete three-dimensional folding of the single polypeptide, while the quaternary structure is the arrangement of multiple folded polypeptides in a multisubunit complex.

Understanding the complex folding of polypeptide chains to form functional proteins is critical, as it determines how proteins interact with other molecules within cells and carry out their activities. Disruptions in protein structure can lead to significant biological consequences and are often at the root of many diseases.