What structural level is represented by the coiling of the protein chain backbone into an alpha helix?
primary structure
quaternary structure
secondary structure
tertiary structure
The Correct Answer is C
A. Primary structure: The primary structure refers to the linear sequence of amino acids in a polypeptide chain. It does not include any folding or coiling of the chain.
B. Quaternary structure: Quaternary structure arises when multiple polypeptide chains or subunits associate to form a functional protein complex. It is not related to the coiling of a single chain.
C. Secondary structure: Secondary structure is characterized by local folding patterns of the polypeptide backbone, including alpha helices and beta sheets, stabilized by hydrogen bonds between backbone atoms. The alpha helix is a classic example of this level of structure.
D. Tertiary structure: Tertiary structure refers to the overall three-dimensional folding of a single polypeptide chain, determined by interactions between side chains, not the regular coiling of the backbone.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
A. Proteins: Proteins serve as the primary structural components of cells and tissues. They form muscles, connective tissue, enzymes, and cell membranes, providing strength, support, and functional versatility throughout the body.
B. Carbohydrates: Carbohydrates primarily provide energy and serve as short-term fuel and structural components like glycogen, but they are not the main structural material of the body.
C. Lipids: Lipids function as energy storage, insulation, and components of cell membranes, but they do not provide the bulk structural framework of tissues.
D. Nucleic acids: Nucleic acids such as DNA and RNA store and transmit genetic information but do not serve as the primary structural material for the body.
Correct Answer is A
Explanation
A. The enzyme will denature and become inactive: Salivary amylase works best at a neutral to slightly basic pH, such as in the mouth. Once it reaches the stomach, the highly acidic environment disrupts its three-dimensional structure, causing denaturation and loss of activity
B. The enzyme will continue to function as it remains unchanged in chemical reactions: While enzymes are not consumed in reactions, their activity depends on pH and temperature. At a gastric pH of 2.5, salivary amylase cannot maintain its shape, so it stops functioning.
C. The enzyme will assume an alternate form and catalyze additional reactions: Enzymes are highly specific to their structure and active site. Once denatured, they do not take on new functional forms or catalyze new reactions.
D. The enzyme will denature but retain its function: Denaturation disrupts the enzyme’s active site, preventing substrate binding. If the enzyme denatures, it loses its catalytic ability entirely and cannot retain its original function.
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