Question

An alpha helix is an example of a. primary protein structure. b. secondary protein structure. c. tertiary protein structure. d. quaternary protein structure.

Short answer

b. secondary protein structure

Step-by-step solution

Understand Protein Structures

Proteins have four levels of structure: primary, secondary, tertiary, and quaternary. Each level has unique characteristics.

Define Secondary Protein Structure

Secondary structures are local folded structures that form within a polypeptide due to hydrogen bonding between backbone atoms. Common examples include alpha helices and beta sheets.

Identify Alpha Helix

An alpha helix is a right-handed coil where the backbone forms a helical structure stabilized by hydrogen bonds. This is a type of secondary protein structure.

Select the Correct Option

Since an alpha helix is a type of secondary protein structure, the correct answer is b. secondary protein structure.

Key concepts

secondary protein structure

Proteins, complex molecules in the body, have structures organized at multiple levels. The secondary protein structure refers to local folded shapes within a single polypeptide chain. These structures arise due to hydrogen bonding between the amino acids' backbone atoms. Two common types of secondary structures are alpha helices and beta sheets.
The alpha helix is a right-handed coil where hydrogen bonds stabilize the helical turns. On the other hand, beta sheets consist of stretched-out strands connected side-by-side through hydrogen bonds. These structures play a crucial role in defining the protein's overall shape and its function.

hydrogen bonding

Hydrogen bonding is a key force in stabilizing protein structures. It occurs between a hydrogen atom, usually bonded to oxygen or nitrogen, and an electronegative atom within the polypeptide chain. In secondary protein structures, these bonds are pivotal.
For alpha helices, hydrogen bonds form every four amino acids, creating a snug, spiral shape. In beta sheets, hydrogen bonds connect the strands linearly, stabilizing the sheet-like formations. Understanding hydrogen bonding helps explain how specific shapes like alpha helices and beta sheets are formed and maintained in proteins.

protein folding

Protein folding is the process through which a polypeptide chain attains its functional three-dimensional form. It starts from a simple, linear sequence of amino acids to a uniquely folded shape. Folding is driven by various interactions, including hydrogen bonds, hydrophobic interactions, and ionic bonds.
During folding, secondary structures like alpha helices and beta sheets arise first. These elements then arrange into more complex structures, leading to the functional form of the protein. Proper folding is essential; misfolding can lead to diseases like Alzheimer's.

protein structure levels

Proteins have four distinct levels of structure, each crucial for their function:

• Primary Structure: The linear sequence of amino acids in the polypeptide chain.
• Secondary Structure: Local structures like alpha helices and beta sheets formed through hydrogen bonding.
• Tertiary Structure: The overall 3D shape of a single polypeptide chain, including all secondary structures, stabilized by various interactions.
• Quaternary Structure: The assembly of multiple polypeptide chains into a single functional protein complex.

These levels illustrate how a simple sequence of building blocks can lead to a highly complex and functional molecule.