What level of protein synthesis is represented by the coiling of the protein chain backbone into an alpha helix?
secondary structure
primary structure
tertiary structure
quaternary structure
The Correct Answer is A
A. Secondary structure: The secondary structure of a protein involves local folding patterns of the polypeptide backbone, including alpha helices and beta sheets, stabilized by hydrogen bonds between backbone atoms. The coiling into an alpha helix is a classic example of this level.
B. Primary structure: The primary structure is the linear sequence of amino acids in the polypeptide chain, without any folding or coiling.
C. Tertiary structure: Tertiary structure refers to the overall three-dimensional folding of a single polypeptide chain due to interactions between side chains, not the coiling of the backbone.
D. Quaternary structure: Quaternary structure arises when multiple polypeptide chains or subunits come together to form a functional protein complex, beyond the level of alpha helix formation.
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Related Questions
Correct Answer is B
Explanation
A. Molecular weight of a substance does not affect the rate: The molecular weight affects diffusion because larger molecules move more slowly than smaller ones. Heavier molecules have lower kinetic energy at a given temperature, which slows their movement across membranes.
B. The greater the concentration gradient, the faster the rate: Net diffusion is directly influenced by the difference in concentration between two areas. A steeper concentration gradient increases the driving force for molecules to move, resulting in a faster diffusion rate.
C. The rate is independent of temperature: Temperature affects diffusion because higher temperatures increase the kinetic energy of molecules, making them move faster. Therefore, diffusion rates are not independent of temperature.
D. The lower the temperature, the faster the rate: Lower temperatures reduce molecular motion and kinetic energy, which slows diffusion. Faster diffusion occurs at higher temperatures rather than lower ones.
Correct Answer is B
Explanation
A. Hold carbohydrates and DNA in their 3-D shape: Carbohydrates rely more on glycosidic bonds and branching patterns for their structure, while hydrogen bonding has only a minor role. DNA, however, depends heavily on hydrogen bonds between nitrogenous bases for stability.
B. Hold proteins and DNA in their 3-D shape: Proteins maintain their secondary and tertiary structures through hydrogen bonds between amino acid side chains and peptide backbones. DNA depends on hydrogen bonds between complementary bases, which provide stability while still allowing strand separation during replication.
C. Hold carbohydrates and triglycerides in their 3-D shape: Triglycerides are primarily stabilized by ester bonds and hydrophobic interactions. Carbohydrates do not depend significantly on hydrogen bonds for their three-dimensional organization.
D. Hold proteins and RNA in their 3-D shape: While RNA can fold into complex structures stabilized partly by hydrogen bonds, proteins and DNA are more classically described as relying on hydrogen bonding for maintaining stable 3-D conformations.
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