Questions: Consider the different types of metabolic pathways. Which of the following is a metabolic pathway that involves the same set of reactions repeated on increasingly smaller substrates? Select the single best answer. cyclic chain spiral linear Which of the following is a spiral pathway? Select the single best answer. glycolysis pyruvate oxidation the citric acid cycle B-oxidation of fatty acids gluconeogenesis

The answer to Part 1 is: spiral

Explanation for each option:

• Wave: This is not a recognized term in the context of metabolic pathways.
• Cyclic: In cyclic pathways, the end product of the pathway regenerates the initial substrate, allowing the cycle to continue. An example is the citric acid cycle.
• Chain: Chain pathways involve a series of reactions where the product of one reaction becomes the substrate for the next, but they do not involve the same set of reactions repeated on increasingly smaller substrates.
• Spiral: Spiral pathways involve a set of reactions that are repeated, with each cycle processing a progressively smaller substrate. An example is the β-oxidation of fatty acids.
• Linear: Linear pathways involve a series of reactions that proceed in a straight line from the initial substrate to the final product, without repeating the same set of reactions.

The answer to Part 2 is: B-oxidation of fatty acids

Explanation for each option:

• Glycolysis: This is a linear pathway where glucose is broken down into pyruvate.
• Pyruvate oxidation: This is a single-step process that converts pyruvate into acetyl-CoA.
• The citric acid cycle: This is a cyclic pathway where acetyl-CoA is oxidized to CO2 and H2O.
• B-oxidation of fatty acids: This is a spiral pathway where fatty acids are broken down into acetyl-CoA units through repeated cycles of reactions.
• Gluconeogenesis: This is a linear pathway that synthesizes glucose from non-carbohydrate precursors.

Summary: Part 1: The answer is spiral. Part 2: The answer is B-oxidation of fatty acids.