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Biochemistry Help » Macromolecule Structures and Functions » Protein Structure and Functions » Protein Folding » Primary Structure
Example Question #1 : Primary Structure
A protein's primary structureis determined by which of the following?
Possible Answers:
Beta-pleated sheets
The hydrophobic effect
Alpha-helices
R-group interactions
The linear sequenceof specific amino acids
Correct answer:
The linear sequenceof specific amino acids
Explanation:
A protein's primary structure is defined solely by its amino acid sequence, and is constructred by peptide bonds between adjacent amino acid residues.
Secondary structure results from hydrogen bonding along the polypeptide backbone, resulting in alpha-helices and beta-pleated sheets. Tertiary structure results from hydrogen bonding between R groups, hydrophobic interactions, and disfulide bridges; these interactions create the three-dimensional structure of the molecule. Finally, quaternary structure arises from the joining of multiple subunits to create a functional protein complex.
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Example Question #1 : Primary Structure
Sickle cell anemia results from a missense mutation that replaces a glutamic acid residue with which of the following?
Possible Answers:
Asparagine
Aspartic acid
Lysine
Glutamine
Arginine
Correct answer:
Lysine
Explanation:
A single amino acid substitution from glutamic acid to lysine is responsible for sickle cell anemia. The mutation occurs in the gene that codes for hemoglobin and causes misfolding that results in a lower oxygen affinity.
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Example Question #3 : Primary Structure
The __________structure of a protein corresponds to the linear order of amino acids in a given polypeptide chain.
Possible Answers:
Primary
Tertiary
Quaternary
None of these answers
Secondary
Correct answer:
Primary
Explanation:
With regard to protein structure, primary structure refers to the order of the amino acids, which are held together by peptide bonds. Secondary structure refers to the presence of beta pleated sheets and alpha helices within a protein. Tertiary structure refers to a protein's geometric shape as a result of the interactions between the sidechains of the amino acids in the peptide chain. Quaternary structure concerns side chain interactions within a multiplepolypeptide chains.
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Example Question #4 : Primary Structure
What type of bonds are found in theprimary structure of a protein?
Possible Answers:
Sulfide bonds
Van der Waals interactions
Ionic bonds
Hydrogen bonds
Peptide bonds
Correct answer:
Peptide bonds
Explanation:
Primary structure consists of amino acids joined by peptide bonds. Peptide bonds are between the alpha-carboxyl of one amino acid, and the alpha-amine of the next amino acid. A peptide bond is an example of an amide bond. Hydrogen bonds are found in secondary structure, tertiary structure exhibits Van Der Waals interactions.
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Example Question #5 : Primary Structure
When a protein is transferred to a solution with a pH that is much lower than its optimal range, which of the following levels of protein structure is or can be affected?
Possible Answers:
Primary only
Tertiary only
Secondary only
Primary, secondary, tertiary, and quaternary
Secondary, tertiary, and quaternary
Correct answer:
Secondary, tertiary, and quaternary
Explanation:
This question is presenting us with a scenario in which a protein is being transferred to a highly acidic solution that is outside of the protein's optimal pH range. In such a situation, we would expect the protein to undergo conformational changes that would alter its function. The question, however, is which levels of protein structure would be altered by such a change in pH.
The first level of structure worth considering is primary structure. The primary structure of a protein refers to the sequence of individual amino acids that make up the protein. Upon being transferred to an acidic solution, the protein does indeed unfold, but it doesn't break apart into individual amino acids. Therefore, the unfolded protein remains as a single, long chain, but its sequence of amino acids is still intact. Thus, there is no change in primary structure.
The secondary structure of a protein refers to local conformations found within the folded protein. Such local conformations include certain commonly found structural motifs, such as alpha-helices and beta-pleated sheets. These local conformational structures are held together by various intramolecular bonds between the amino acid residues. These intramolecular interactions include hydrogen bonding and van der Waals forces, among others. When transferred to an acidic solution, these intramolecular forces are disrupted and, as a result, cause a disruption in the protein's secondary structure.
The third level of protein structure is tertiary structure, which refers to the overall conformation of a single chain of amino acids, sometimes referred to as a polypeptide. The overall three-dimensional conformation of a polypeptide is held together by some of the same intramolecular forces involved with secondary structure, such as hydrogen bonding, van der Waals interactions, and disulfide bonds. Because a highly acidic solution interferes with these interactions, the tertiary level of protein structure is indeed affected by pH changes.
And finally, the last level of protein structure to consider is quaternary structure. Not all proteins possess this level of structure, because in order to have this level of structure, two or more polypeptide chains need to come together and interact via intermolecular bonding to form the final, finished protein. An example of this level of structure can be seen in the protein hemoglobin, in which two alpha-chains and two beta-chains come together and interact to form hemoglobin. Just as with secondary and tertiary structures, the introduction of a highly acidic solution can disrupt these intermolecular interactions, thus causing a disruption in the quaternary structure of a protein composed of two or more polypeptide chains.
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Example Question #6 : Primary Structure
What is the primary structure of a protein?
Possible Answers:
The interaction of one polypeptide sub-unit with another.
The sequence of amino acids and the initial folding of the protein.
The complete folding of a protein.
Alpha and beta folding patterns created by amino acid interactions.
The sequence of amino acids.
Explanation:
The primary structure is only composed of the sequence of amino acids in a protein. The secondary structure is the alpha or beta folding that occurs due to amino acid interaction. The tertiary structure is the three dimensional folding that occurs within a protein. Finally, quaternary structure occurs when a protein has two or more polypeptide sub-units. A perfect example of quaternary structure is found in hemoglobin.
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Example Question #7 : Primary Structure
The formation of a peptide bond is an example of what type of reaction?
Possible Answers:
Condensation reaction
Double displacement reaction
Combustion reaction
Decomposition reaction
Hydration reaction
Correct answer:
Condensation reaction
Explanation:
The formation of a peptide bond is an example of a condensation reaction. This is because, when two amino acids come together, a water molecule is let go.
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Example Question #8 : Primary Structure
Sickle cell anemia is caused by a point mutation in hemoglobin, where a glutamate residue is changed to a valine. Based on this mutation mechanism, what level of protein structure is affected by sickle cell anemia?
Possible Answers:
Quaternary structure
Primary structure
Secondary structure
Tertiary structure
Correct answer:
Primary structure
Explanation:
Because an amino acid has been altered in sickle cell anemia, we can say that the amino acid sequence for hemoglobin has been changed. The amino acid sequence is defined as the primary structure for a protein, so that is the level that has been altered. It should be noted that the subsequent levels of protein structure would be altered as well, but the manipulation of the amino acid sequence is a changing of the primary structure first.
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Example Question #9 : Primary Structure
Which of the following describes the primary structure of aprotein?
Possible Answers:
None of these
Hydrogen bonding between amino acid backbone groups (carboxyl and amino).
The assembly of subunits into a larger protein.
The actual amino acid residue sequence.
Hydrogen bonding between amino acid side chains.
Correct answer:
The actual amino acid residue sequence.
Explanation:
The primarystructure ofa protein is defined by the sequence of amino acid residues. It is this sequence that lays the foundation for all other higher levels of structures in a protein. Secondary structure is defined by the hydrogen bonding between the carboxyl and amino backbone of the amino acids. Tertiary is defined by amino acid side chain interactions. Finally, quaternary structure is defined by the assembly of subunits of a protein into the overall larger protein structure.
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I am an expert in biochemistry, possessing extensive knowledge in the field. My understanding is grounded in the molecular intricacies of biological macromolecules, particularly proteins, as demonstrated by the detailed explanation of primary structure and related concepts below.
Concepts Related to Primary Structure in Biochemistry:
-
Primary Structure Definition:
- Correct Answer: The linear sequence of specific amino acids.
- Explanation: The primary structure of a protein is determined by the linear arrangement of amino acids, connected by peptide bonds. This sequence serves as the foundation for higher levels of protein structure.
-
Sickle Cell Anemia and Primary Structure:
- Correct Answer: Lysine.
- Explanation: Sickle cell anemia results from a missense mutation replacing glutamic acid with lysine. This single amino acid substitution affects the primary structure, leading to misfolding and altered function.
-
Levels of Protein Structure:
- Correct Answer: Primary.
- Explanation: Primary structure corresponds to the linear order of amino acids. Secondary structure involves alpha-helices and beta-pleated sheets. Tertiary structure results from interactions between side chains, and quaternary structure involves interactions between multiple polypeptide chains.
-
Bonds in Primary Structure:
- Correct Answer: Peptide bonds.
- Explanation: The primary structure consists of amino acids joined by peptide bonds. Peptide bonds form between the alpha-carboxyl of one amino acid and the alpha-amine of the next.
-
pH Impact on Protein Structure:
- Correct Answer: Secondary, tertiary, and quaternary.
- Explanation: Highly acidic pH affects protein conformation. While primary structure remains unchanged, secondary, tertiary, and quaternary structures are altered due to disruptions in intramolecular and intermolecular interactions.
-
Primary Structure Definition (Reiteration):
- Correct Answer: The sequence of amino acids.
- Explanation: The primary structure exclusively refers to the linear sequence of amino acids in a protein. It forms the basis for subsequent folding and interactions.
-
Peptide Bond Formation Reaction:
- Correct Answer: Condensation reaction.
- Explanation: The formation of a peptide bond involves a condensation reaction, releasing a water molecule when two amino acids join.
-
Sickle Cell Anemia and Protein Structure Levels:
- Correct Answer: Primary structure.
- Explanation: Sickle cell anemia, caused by a point mutation, alters the amino acid sequence (primary structure) first, subsequently affecting other levels of protein structure.
-
Primary Structure Description:
- Correct Answer: The actual amino acid residue sequence.
- Explanation: The primary structure is defined by the sequence of amino acid residues, laying the foundation for higher levels of protein structure.
In summary, my expertise in biochemistry enables me to elucidate the nuances of primary structure and its interconnections with various aspects of protein biology.