GRE Subject Test: Biochemistry, Cell, and Molecular Biology : Help with Protein Structures

Study concepts, example questions & explanations for GRE Subject Test: Biochemistry, Cell, and Molecular Biology

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Example Questions

Example Question #1 : Help With Protein Structures

Which of the level of protein structure is incorrectly matched to its description?

Possible Answers:

Primary structure is the linear amino acid sequence of a protein

Quaternary structure is the three-dimensional structure of a multi-subunit protein

Secondary structure is determined by hydrogen bonding of the amino acid backbone

Tertiary structure is the two-dimensional structure of a protein

Correct answer:

Tertiary structure is the two-dimensional structure of a protein

Explanation:

Primary structure of a protein is determined by covalent peptide bonds, and corresponds to the linear sequence of amino acids before structures begin to form. Secondary structure results from hydrogen bonding between the amino acid backbones to form alpha-helices and beta-sheets. Tertiary structure is formed when functional groups of the amino acids interact, either by hydrogen bonding, hydrophobic interactions, or disulfide bridge formation. Tertiary structure is associated with the three-dimensional structure of a single polypeptide chain. Quaternary structure forms when multiple polypeptide chains interact to build a multi-subunit structure.

Example Question #1 : Help With Protein Structures

Which of the following proteins are likely to contain leucine zipper domains?

Possible Answers:

Proteases

Transcription factors

Lipases

Transmembrane proteins

Correct answer:

Transcription factors

Explanation:

Leucine zippers are domains that allow for the binding of DNA. The question is essentially asking, "which of these proteins are capable of binding DNA?"

Proteases cleave proteins, lipases hydrolyze lipids, and transmembrane proteins interact with membranes. Transcription factors are the only given proteins that bind DNA and, therefore, are much more likely to contain leucine zipper domains than the other options. 

Example Question #2 : Help With Protein Structures

Which protein structure involves the binding of multiple polypeptides?

Possible Answers:

Quaternary structure

Primary structure

Tertiary structure

Secondary structure

Correct answer:

Quaternary structure

Explanation:

The structures of a protein increase in complexity all the way up to quaternary structure. Primary structure is based on the amino acid sequence of the protein, while secondary and tertiary structures are based on intermolecular attractions between the amino acids in the polypeptide. Quaternary structure is only seen when a functional protein complex is composed of two or more polypeptides bound together.

Example Question #3 : Help With Protein Structures

Disulfide bonds in proteins are categorized under which structure class? 

Possible Answers:

More than one of these

Tertiary structure

Secondary structure

Primary structure

Quaternary structure

Correct answer:

More than one of these

Explanation:

The correct answer is more than one of these. Primary structure is defined as a succession of amino acids joined by peptide bonds. Secondary structure introduces dimensionality to a protein via hydrogen bonding to produce two predominant structures, alpha helices and beta-pleated sheets. Tertiary structures cause further protein folding by disulfide bonds between cysteines, Van der Waal interactions, and hydrophobic interactions. Quaternary structures involve multiple amino acid chains folding together, and utilize the same types of bonds as tertiary structures. 

All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources

1 Diagnostic Test 201 Practice Tests Question of the Day Flashcards Learn by Concept
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