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Questions and Answers
What type of bond links amino acids together to form the primary structure of a protein?
What type of bond links amino acids together to form the primary structure of a protein?
The formation of a peptide bond is an endergonic (requires energy input) reaction.
The formation of a peptide bond is an endergonic (requires energy input) reaction.
True
What are the two ends of a polypeptide chain called?
What are the two ends of a polypeptide chain called?
Amino-terminal (N-terminal) and Carboxyl-terminal (C-terminal)
The main chain of a polypeptide includes a regularly repeating portion consisting of the amino group, the alpha carbon with hydrogen, and the ______ group.
The main chain of a polypeptide includes a regularly repeating portion consisting of the amino group, the alpha carbon with hydrogen, and the ______ group.
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Which of the following is considered the variable portion of an amino acid in a polypeptide chain?
Which of the following is considered the variable portion of an amino acid in a polypeptide chain?
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Oligopeptides contain more than 50 amino acids.
Oligopeptides contain more than 50 amino acids.
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What type of covalent bond is formed by the oxidation between two cysteine residues?
What type of covalent bond is formed by the oxidation between two cysteine residues?
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Match the following terms with their descriptions:
Match the following terms with their descriptions:
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Besides determining the 3D structure of a protein, name two other reasons that the amino acid sequence of a protein is important.
Besides determining the 3D structure of a protein, name two other reasons that the amino acid sequence of a protein is important.
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In a polypeptide chain, the ________ group is a good hydrogen-bond donor.
In a polypeptide chain, the ________ group is a good hydrogen-bond donor.
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Which type of bond is primarily responsible for linking amino acids together to form a polypeptide chain?
Which type of bond is primarily responsible for linking amino acids together to form a polypeptide chain?
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The peptide bond has free rotation, allowing proteins to fold into many conformations.
The peptide bond has free rotation, allowing proteins to fold into many conformations.
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What is the primary driving force behind protein folding?
What is the primary driving force behind protein folding?
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In an alpha helix, hydrogen bonds form between the CO group and the NH group of amino acids located ______ amino acids away in the chain.
In an alpha helix, hydrogen bonds form between the CO group and the NH group of amino acids located ______ amino acids away in the chain.
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Match the secondary structure with its description:
Match the secondary structure with its description:
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Which amino acids are known to destabilize alpha helices due to branching at the β-carbon?
Which amino acids are known to destabilize alpha helices due to branching at the β-carbon?
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In beta sheets, side chains of adjacent amino acids point in the same direction.
In beta sheets, side chains of adjacent amino acids point in the same direction.
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What type of interactions are responsible for maintaining quaternary structure?
What type of interactions are responsible for maintaining quaternary structure?
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A protein that has lost its normal shape and thus function is said to be ______.
A protein that has lost its normal shape and thus function is said to be ______.
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Which of the following is NOT a typical interaction found in the tertiary structure of a protein?
Which of the following is NOT a typical interaction found in the tertiary structure of a protein?
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Study Notes
Protein Three-Dimensional Structure
- Protein structure is described at four levels: primary, secondary, tertiary, and quaternary.
- The relationship between protein structure and function is crucial.
Primary Structure
- Amino acids are linked by peptide bonds to form polypeptide chains.
- These bonds form via a dehydration synthesis reaction, losing a water molecule and requiring energy.
- Peptide bonds are highly stable.
- Polypeptide chains have directionality (N-terminus to C-terminus).
- The precise sequence of amino acids defines the primary structure.
Secondary Structure
- Polypeptide chains fold into regular structures, stabilized by hydrogen bonds.
- Hydrogen bonds form between NH and CO groups of amino acids close in the primary sequence.
- Common secondary structures include: alpha helices and beta pleated sheets.
- Loops and turns are also found in secondary structure.
- Side chains project outward.
Alpha Helix
- A coiled, rod-like structure.
- ~3.6 amino acids per turn.
- Hydrogen bonds form between the peptide backbone carbonyl oxygen and the amide hydrogen four residues away.
- Side chains point outward from the helix axis.
- Specific amino acids (e.g., Proline, Glycine, and bulky hydrophobic residues) can disrupt the helix.
Beta Sheets
- Formed by more than one polypeptide strand or segments that align side-by-side.
- Strands can be parallel or antiparallel.
- Hydrogen bonds form between the strands.
- Side chains project above and below the plane of the sheet.
Turns and Loops
- Loops and turns are frequently found on the protein surface.
- They allow the polypeptide chain to change direction, connecting different secondary structures.
Tertiary Structure
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The overall three-dimensional arrangement of all amino acids in the polypeptide chain.
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Water-soluble proteins fold into compact structures.
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Hydrophobic side chains tend to be buried inside the protein, away from water.
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Polar side chains tend to be on the surface, interacting with water.
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Disulfide bonds contribute to the protein's stability.
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Van der Waals interactions and other interactions contribute to overall stability.
Quaternary Structure
- Multiple polypeptide chains can assemble into a single functional protein.
- Subunits (individual polypeptide chains) interact via weak interactions (hydrogen bonds, ionic bonds, and van der Waals forces).
- Number of subunits, type, and arrangement vary.
Amino Acid Sequence and Protein Structure
- The amino acid sequence dictates the protein's three-dimensional structure.
- Denatured proteins lose their structure and function. Under specific conditions they can return to their original structure, otherwise they require chaperones.
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Description
This quiz explores the fundamental concepts of protein structure, focusing on amino acids and peptide bonds. Learn about the importance of these bonds, the organization of polypeptide chains, and the significance of amino acid sequences in protein functionality. Test your knowledge on the primary structure of proteins and their covalent interactions.
