Biochemistry : Tertiary Structure

Study concepts, example questions & explanations for Biochemistry

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Example Questions

Example Question #1 : Tertiary Structure

Which of the following statements are true about protein structure?

Possible Answers:

pH does not change the charge of a protein

All proteins have a quaternary structure

None of the other answers are true

Disulfide bridges primarily maintain secondary structures, as opposed to tertiary

A protein’s function depends on its spatial conformation

Correct answer:

A protein’s function depends on its spatial conformation

Explanation:

Not all proteins have a quaternary structure; quaternary structure refers to the arrangement and number of subunits, and not every protein has multiple subunits. Disulfide bonds make proteins less susceptible to unfolding; typically, they will link -sheets, -helices, and loops, which means that they primarily maintain tertiary structure, not secondary, which refers to local conformations, and is maintained largely by hydrogen bonds. Protein charges do change with pH; as a solution’s pH increases, acidic groups on proteins deprotonate. A protein’s function depends, however, very much on its spatial conformation. Its native conformation permits it to recognize and bind to specific molecules, and thus perform its specific function.

Example Question #2 : Tertiary Structure

Which of the following does not stabilize the tertiary structure of a protein?

Possible Answers:

Hydrogen bonds

Amide bonds

Salt bridges

Hydrophobic interactions

Disulfide bonds

Correct answer:

Amide bonds

Explanation:

Tertiary structure is stabilized by multiple interactions, specifically side chain functional groups which involve hydrogen bonds, salt bridges, covalent disulfide bonds, and hydrophobic interactions. Amide bonds do not contribute to the stability of a protein's secondary structure, rather, peptide bonds are amide bonds that stabilize a protein's primary structure..

Example Question #3 : Tertiary Structure

Formation of a disulfide bond is what type of reaction?

Possible Answers:

Oxidation

 

Glycosylation

Reduction

Correct answer:

Oxidation

Explanation:

During the formation of a disulfide bond, two free  groups lose their bond to hydrogen and form an  bond. This loss of bonds to hydrogen means it is an oxidation reaction. 

Example Question #4 : Tertiary Structure

In a soluble protein that resides in the cytoplasm, where is the majority of the nonpolar amino acids found in its three-dimensional structure?

Possible Answers:

On the surface of the protein

Localized to the N-terminus of the protein

Randomly interspersed throughout to protein

Localized to the C-terminus of the protein

Buried in the center of the protein

Correct answer:

Buried in the center of the protein

Explanation:

In order for a protein to stay soluble in the cell, it needs to have a hydrophilic surface that can interact with water and and hydrophobic regions need to be contained in its center. Therefore polar, hydrophilic amino acids are mostly found on the surface of a protein's 3D structure while non polar hydrophobic residues are usually found on buried in the core of a proteins 3D structure.

Example Question #75 : Macromolecule Structures And Functions

What is the overall folding of one protein subunit called?

Possible Answers:

Primary structure

Quaternary structure

Tertiary structure

Secondary structure

Correct answer:

Tertiary structure

Explanation:

Proteins are made of primary, secondary, tertiary, and sometimes quaternary structure. The primary structure of a protein involves the amino acid sequence in the polypeptide chain. The amino acids in this chain are held together by peptide bonds. The secondary structure of a protein involves the pattern of hydrogen bonds along the its peptide bond backbone, such as alpha helices and beta pleated sheets. The tertiary structure of a protein is the final specific shape of one subunit; this is determined by bonding interactions between the amino acid side chains. Some proteins consist of quaternary structure, which is the number and arrangement of multiple folded subunits.

Example Question #5 : Tertiary Structure

Which of the following is not a component of tertiary structure?

Possible Answers:

Disulfide bonds

Ionic bonds

Hydrogen bonds

Interactions between two or more sub-units

Hydrophobic interactions

Correct answer:

Interactions between two or more sub-units

Explanation:

The tertiary structure of a protein is the three dimensional shape of the protein. Disulfide bonds, hydrogen bonds, ionic bonds, and hydrophobic interactions all influence the shape a protein takes. Quaternary structure is the level that deals with multiple sub-units folding together. An example of quaternary structure is hemoglobin, composed of four sub-units. 

Example Question #6 : Tertiary Structure

2-mercaptoethanol is a chemical agent used in denaturing proteins. Its primary method of denaturing involves separating disulfide bonds. Based on this method of denaturation, what is the lowest level of protein structure affected by 2-mercaptoethanol?

Possible Answers:

Primary structure

Secondary structure

Quaternary structure

Tertiary structure

Correct answer:

Tertiary structure

Explanation:

A disulfide bond is created by two cysteine residues coming together and creating a sulfur-sulfur linkage. This type of linkage contributes to the tertiary structure of proteins. It can also be seen in quaternary structure between peptide subunits, but tertiary structure is the first level where this force can be observed.

Example Question #78 : Macromolecule Structures And Functions

Which of the following statements are true about protein domains?

I. Polypeptide chains longer than 200 amino acids in length have multiple domains.

II. Domains are tertiary structural components of proteins.

III. Different domains are encoded by different exons of a gene.

IV. Each domain in a protein has a specific function.

Possible Answers:

II, III, and IV

I and IV

I, II, III, and IV

I, II, and III

II and IV

Correct answer:

I, II, III, and IV

Explanation:

Domains are tertiary structures that have motifs (a supersecondary structure) as their components. Domains are independent (functionally and structurally) from each other.

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