Biochemistry : Identifying Specific Protein Structures

Study concepts, example questions & explanations for Biochemistry

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Example Questions

Example Question #42 : Identification By Structure

Describe the solubility of the given amino acids.

Phenylalanine and Tyrosine

Possible Answers:

Cannot be determined without knowing the temperature of the solution

Neither are soluble

Both are equally soluble

Tyrosine < Phenylalanine

Phenylalanine < Tyrosine

Correct answer:

Phenylalanine < Tyrosine

Explanation:

Although tyrosine is hydrophobic, it is more soluble than phenylalanine. The only difference between the two amino acids is the hydroxyl group present on tyrosine. The hydroxyl is much more acidic than the hydrogen, and so it is more likely to ionize. The ability to ionize makes it more soluble (think electrolytes). 

Example Question #43 : Identification By Structure

Identify the given amino acid.

Aspartic acid

Possible Answers:

Myristic acid

Asparagine

Alanine

Aspartic acid

Glutamic acid

Correct answer:

Aspartic acid

Explanation:

Aspartic acid is an acidic amino acid, meaning it contains  in its R-group. The R-group of aspartic acid is .

Example Question #46 : Identification By Structure

Identify the given structure.

Phenylalanine

Possible Answers:

Phenylalanine

Proline

Tryptophan

Tyrosine

Histidine

Correct answer:

Phenylalanine

Explanation:

Phenylalanine is a non-polar amino acid. The structure of this amino acid is literally alanine with a phenyl group attached.

Example Question #44 : Identification By Structure

Which of the following structures is threonine?

Possible Answers:

Aspartic acid

Asparagine

Alanine

Threonine

Arginine

Correct answer:

Threonine

Explanation:

Threonine is a polar uncharged amino acid with a  R-group.

Example Question #48 : Identification By Structure

Identify the given structure.

Arginine

Possible Answers:

Arginine

Leucine

Aspartic acid

Alanine

Lysine

Correct answer:

Arginine

Explanation:

Arginine is a basic amino acid. The charge on the amine in the functional group makes this structure basic. While lysine is also a basic amino acid, it has a different R-group.

Example Question #51 : Identification By Structure

Which of the following structures is cysteine?

Possible Answers:

Cysteine

Threonine

Methionine

Asparagine

Alanine

Correct answer:

Cysteine

Explanation:

Cysteine is a polar amino acid with an R-group of . It is one of two amino acids with a sulfur in the R-group, the other is methionine. 

Example Question #52 : Identification By Structure

Which of the following is an acidic amino acid?

Possible Answers:

Asparagine

Methionine

Threonine

Arginine

Aspartic acid

Correct answer:

Aspartic acid

Explanation:

An acidic amino acid must have a carboxyl moiety  in its R-group. Because all amino acids contain a carboxyl moiety on the alpha carbon, that acidic group does not determine whether or not the amino acid is considered acidic.

Example Question #17 : Identifying Specific Protein Structures

Which of the following statements best describes high-density lipoproteins as compared to other lipoproteins?

Possible Answers:

They have the most triglycerides and least protein

They have more triglycerides than very low-density lipoproteins

They have the highest protein content

They have the highest content of cholesterol and cholesterol esters

Correct answer:

They have the highest protein content

Explanation:

High-density lipoproteins have the highest proportion of protein of the five classes of blood lipoproteins: chylomicrons, very-low-density lipoproteins, intermediate-density lipoproteins, low-density lipoproteins, and high-density lipoproteins. Chylomicrons have the lowest density of the five classes of lipoproteins. This is because the have the highest proportion of triglycerides and the least lowest proportion of protein. Very-low-density lipoproteins are a bit more dense than chylomicrons; however, the relative amount of triglycerides is still high. Intermediate-density lipoproteins which are formed from the very-low-density lipoproteins have a higher density than very-low-density lipoproteins due to the fact that they have less than half of the amount of triglycerides as very-low-density lipoproteins. Low-density lipoproteins have the highest amount of cholesterol and an even lesser amount of triglycerides than intermediate-density lipoproteins. Lastly, high-density lipoproteins are the densest of the lipoproteins due to the fact that they have the highest amount of protein in relation to the amount of triglycerides they contain.

Example Question #17 : Identifying Specific Protein Structures

Which of the following statements best describes chylomicrons as compared to other lipoproteins?

Possible Answers:

They have the most triglycerides and least protein

The have a higher density then high-density lipoproteins

They have the highest protein content

They have the highest content of cholesterol and cholesterol esters

Correct answer:

They have the most triglycerides and least protein

Explanation:

There are essentially five classes of blood lipoproteins: chylomicrons, very-low-density lipoproteins, intermediate-density lipoproteins, low-density lipoproteins, and high-density lipoproteins. Chylomicrons have the lowest density of the five classes of lipoproteins. This is because the have the highest proportion of triglycerides and the least lowest proportion of protein. Very-low-density lipoproteins are a bit more dense than chylomicrons; however, the relative amount of triglycerides is still high. Intermediate-density lipoproteins which are formed from the very-low-density lipoproteins have a higher density than very-low-density lipoproteins due to the fact that they have less than half of the amount of triglycerides as very-low-density lipoproteins. Low-density lipoproteins have the highest amount of cholesterol and an even lesser amount of triglycerides than intermediate-density lipoproteins. Lastly, high-density lipoproteins are the densest of the lipoproteins due to the fact that they have the highest amount of protein in relation to the amount of triglycerides they contain.

Example Question #321 : Biochemistry

Which blood lipoprotein has the lowest density of the lipoproteins?

Possible Answers:

Intermediate density lipoproteins

Very-low-density lipoproteins

Low-density lipoproteins

Chylomicrons

Correct answer:

Chylomicrons

Explanation:

Low-density lipoproteins have the highest content of cholesterol and cholesterol esters. There are essentially five classes of blood lipoproteins: chylomicrons, very-low-density lipoproteins, intermediate-density lipoproteins, low-density lipoproteins, and high-density lipoproteins. Chylomicrons have the lowest density of the five classes of lipoproteins. This is because the have the highest proportion of triglycerides and the least lowest proportion of protein. Very-low-density lipoproteins are a bit more dense than chylomicrons; however, the relative amount of triglycerides is still high. Intermediate-density lipoproteins which are formed from the very-low-density lipoproteins have a higher density than very-low-density lipoproteins due to the fact that they have less than half of the amount of triglycerides as very-low-density lipoproteins. Low-density lipoproteins have the highest amount of cholesterol and an even lesser amount of triglycerides than intermediate-density lipoproteins. Lastly, high-density lipoproteins are the densest of the lipoproteins due to the fact that they have the highest amount of protein in relation to the amount of triglycerides they contain.

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