Biochemistry : Identifying Biochemical Molecules

Study concepts, example questions & explanations for Biochemistry

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Example Questions

Example Question #1 : Identifying Specific Protein Structures

Which amino acid does this structure represent?

Glutamate

Possible Answers:

Asparagine

Glutamate

Glutamine

Arginine

Aspartate

Correct answer:

Glutamate

Explanation:

The amino acid's R group is composed of an ethyl group, followed by a carboxylate group, and therefore represents glutamate.

Example Question #2 : Identifying Specific Protein Structures

Which amino acid does this structure represent?

Methionine

Possible Answers:

T

M

A

S

Y

Correct answer:

M

Explanation:

The amino acid's chiral carbon is connected to two methyl groups followed, by a sulfur, and finally another methyl group. Therefore, the amino acid is methionine (M).

Example Question #3 : Identifying Specific Protein Structures

The amino acid phenylalanine is pictured. If a hydroxyl group was added to the carbon in the red box, which amino acid would the new molecule most closely resemble?

Phenylalanine

Possible Answers:

Lysine

Glysine

Alanine

Tyrosine

Arginine

Correct answer:

Tyrosine

Explanation:

The structure would most closely resembe tyrosine (pictured). 

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Example Question #4 : Identifying Specific Protein Structures

If the phenyl group in the pictured molecule were removed, what amino acid would the new structure most closely resemble? 

Phenylalanine

Possible Answers:

Tyrosine

Glycine

Alanine

Valine

Phenylalanine

Correct answer:

Alanine

Explanation:

Alanine is the amino acid that would be formed by removing the phenyl group from phenylalanine (the pictured molecule).

Example Question #5 : Identifying Specific Protein Structures

If the amide group of glutamine (pictured here) was removed and a hydroxyl group was added to the carbon bound to the alpha carbon of the resulting structure, what amino acid would be formed?

Glutamine

Possible Answers:

Methionine

Cysteine

Tyrosine

Threonine

Valine

Correct answer:

Threonine

Explanation:

Threonine (pictured here) would be formed.

 

Threonine

Example Question #6 : Identifying Specific Protein Structures

Which of the following structures is methionine?

Possible Answers:

Methionine

Threonine

Arginine

Aspartic acid

Leucine

Correct answer:

Methionine

Explanation:

Methionine is a non-polar amino acid. It is one of two amino acids that contain sulfur, the other is cysteine.

Example Question #4 : Identifying Specific Protein Structures

Name the given structure.

Leucine

Possible Answers:

Isoleucine

Lysine

Valine

Alanine

Leucine

Correct answer:

Leucine

Explanation:

Leucine is a non-polar amino acid with a  R-group.

Example Question #5 : Identifying Specific Protein Structures

Which of the following is a polar amino acid?

Possible Answers:

Cysteine

Alanine

Leucine

Phenylalanine

Threonine

Correct answer:

Threonine

Explanation:

The polarity of an amino acid is determined by the R-group. The electronegativity difference between oxygen and carbon creates a dipole with the partial positive being on carbon and the partial negative being on oxygen. The dipole makes the molecule polar.

Example Question #5 : Identifying Specific Protein Structures

Which of the following is a basic amino acid?

Possible Answers:

Phenylalanine

Methionine

Aspartic acid

Arginine

Cysteine

Correct answer:

Arginine

Explanation:

Bases, according to the Bronsted-Lowry definition, are substances that  accept 

Arginine is a base

Example Question #1 : Identifying Specific Protein Structures

Identify the given amino acid.

Asparagine

Possible Answers:

Glycine

Asparagine

Glutamic acid

Glutamine

Aspartic acid

Correct answer:

Glutamine

Explanation:

Glutamine is one of two amino acids that are amides. The nitrogen bonded to a carbon-oxygen double bond makes it an amide. 

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