1. structure describes the alpha-helices and beta-sheets that are formed by hydrogen bonding between backbone atoms located near each other in the polypeptide chain. 2. structure is the result of two or more protein subunits assembling to form a larger, biologically active protein complex. 3. structure is achieved when a protein folds into a compact, three-dimensional shape stabilized by interactions between side-chain r groups of amino acids. 4. structure is the sequence of amino acids in a protein.

1. Answer;

-secondary structure;

Explanation;

Protein secondary structure refers to regular, repeated patterns of folding of the protein backbone. The two most common folding patterns are the alpha helix and the beta sheet. In an alpha helix, the polypeptide backbone coils around an imaginary helix axis in clockwise direction. In the beta sheet secondary structure, the polypeptide backbone is nearly fully extended. The R-groups are alternately pointed above and then below the extended backbone.

2. Answer;

- Quaternary structure

Explanation;

-Many proteins are formed from more than one polypeptide chain. The Quaternary structure describes the way in which the different subunits are packed together to form the overall structure of the protein. For example, the human hemoglobin molecule shown below is made of four subunits.

3. Answer;

-Tertiary structure

Explanation;

Tertiary structure refers to the overall folding of the entire polypeptide chain into a specific 3D shape. The tertiary structure of enzymes is often a compact, globular shape.

The tertiary structure is the structure at which polypeptide chains become functional. At this level, every protein has a specific three-dimensional shape and presents functional groups on its outer surface, allowing it to interact with other molecules, and giving it its unique function.

4. Answer;

Primary structure

Explanation;

-It is the simplest level of protein structure and is simply a sequence of amino acids in a polypeptide chain. For example, the hormone insulin has two polypeptide chains, A and B. Each chain has its own set of amino acids, assembled in a particular order. For instance, the sequence of the A chain starts with glycine at the N-terminus and ends with asparagine at the C-terminus, and is different from the sequence of the B chain.