$$m/z = \frac{\text{Masse} + n\text{H}^+}{n}$$

Question 1

Which of the following best describes the primary structure of a protein?

Accepted Answer

The sequence of amino acids linked by covalent peptide bonds

Question 2

Why is it necessary to reduce disulfide bonds before sequencing a protein using Edman degradation?

Accepted Answer

To separate polypeptide chains that are covalently linked, allowing individual sequencing

Question 3

A peptide has a mass of 1060.25 Da and is detected in mass spectrometry with a charge of +1. What is its $$m/z$$ value?

Accepted Answer

$$m/z = 1060.25$$

Question 4

Which protease would you use to specifically cleave a peptide after lysine residues?

Accepted Answer

Trypsin

Question 5

What is the main limitation of Edman degradation for protein sequencing?

Accepted Answer

It is only effective for peptides shorter than about 50 amino acids

Question 6

In mass spectrometry, the $$m/z$$ ratio is calculated as:

Accepted Answer

$$m/z = \frac{	ext{Masse} + n	ext{H}^+}{n}$$

Question 7

Which technique is most suitable for sequencing long peptides and detecting certain post-translational modifications?

Accepted Answer

Mass spectrometry

Question 8

A patient with sickle cell anemia has a mutation in the hemoglobin gene. Which amino acid substitution is responsible for this disease?

Accepted Answer

Glutamate replaced by Valine at position 6 of the beta chain

Question 9

Which of the following statements about protein evolution is correct?

Accepted Answer

Residues that are invariant across species often play essential functional roles

Question 10

Which method allows the identification of the order of amino acids in a peptide by analyzing fragmentation patterns?

Accepted Answer

Tandem mass spectrometry (MS/MS)

Question 11

What is the evolutionary advantage for individuals heterozygous for the sickle cell mutation?

Accepted Answer

Resistance to malaria due to altered red blood cell properties

Question 12

Which of the following is NOT a function of proteins?

Accepted Answer

Storage of genetic information

Question 13

Which protein structure level is directly affected by a point mutation in the DNA sequence coding for the protein?

Accepted Answer

Primary structure

Question 14

Which of the following statements about mass spectrometry is FALSE?

Accepted Answer

It directly measures the mass of peptides

Question 15

Which reagent is commonly used to cleave disulfide bonds in proteins?

Accepted Answer

Dithiothreitol (DTT)

Question 16

A peptide is detected in mass spectrometry with two charge states: $$m/z = 1060.25$$ and $$m/z = 530.63. $$What is the mass of the peptide?

Accepted Answer

$$1060.25 Da$$

Question 17

Which of the following best describes the process of gene duplication in protein evolution?

Accepted Answer

A gene is copied, allowing one copy to retain its original function while the other evolves a new function

Question 18

Which protein is used as a classic example to study evolutionary conservation and phylogenetic relationships?

Accepted Answer

Cytochrome c

Question 19

Which of the following is a limitation of tandem mass spectrometry (MS/MS) in protein sequencing?

Accepted Answer

It cannot distinguish between leucine and isoleucine

Protein Structure and Sequencing Techniques in Biochemistry

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