GRE Subject Test: Biochemistry, Cell, and Molecular Biology : Help with Post-Translational Protein Modification

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 Post Translational Protein Modification

Which of the following is not an example of post-translational modification?

Possible Answers:

Alkylation

Polyadenylation

Myristoylation

Ubiquitination 

Correct answer:

Polyadenylation

Explanation:

Polyadenylation is an example of post-transcriptional modification. This process involves adding large repeats of adenine bases to the 3' end of mRNA molecules, known as the poly-A tail.

Myristoylation is the process of adding myristate (a fatty acid) to a protein, alkylation is the process of adding an alkyl group, and ubiquination is the process of adding a molecule of ubiquitin (a small protein often used to signal degradation). 

Example Question #2 : Help With Post Translational Protein Modification

In which of the following organelles does the initial linkage of a sugar for post-translation modification N-linked glycosylation most commonly occur?

Possible Answers:

Mitochondria

Golgi apparatus

Endoplasmic reticulum

Nucleus

Correct answer:

Endoplasmic reticulum

Explanation:

Two of the more common types of glycosylation, N-linked and O-linked, occur at different points and in different places in the cell. N-linked glycosylation takes place in the lumen of the endoplasmic reticulum, while O-linked glycosylation takes place in the Golgi body.

The other options, the mitochondria and the nucleus, are not involved in these post-translational modifications.

Example Question #3 : Help With Post Translational Protein Modification

Please complete the following statement:

"The addition of a CH3CO group to the N-terminus of a protein is the most common form of protein modification. This chemical modification is called ________."

Possible Answers:

Acetylation

Phosphorylation

Ubiquitination

Adenylation

Methylation

Correct answer:

Acetylation

Explanation:

This question requires knowing either that CH3CO is an acetyl group, or that acetylation is the most common protein modification. Each of the other modifications described are biologically occurring modifications, but acetylation was the correct answer for the given statement. 

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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