Which of the following statements is true regarding metabolic pathways?
A NAD+ is used as a most commonly in anabolic pathways while NADPH is used most commonly in catabolic pathways.
B none of the answers choices are correct.
C catabolic pathways use a wide variety of substrates to produce a small number of waste products.
D atabolic pathways are generally reductive while anabolic pathways are generally oxidative
The correct answer and explanation is :
The correct answer is B. none of the answer choices are correct.
Explanation:
To understand why option B is correct, let’s evaluate each statement:
A. NAD+ is used as a most commonly in anabolic pathways while NADPH is used most commonly in catabolic pathways.
- This statement is incorrect. In fact, the roles of NAD+ and NADPH are often reversed in metabolic pathways. NAD+ is primarily used in catabolic pathways (such as glycolysis, the citric acid cycle) to accept electrons during the breakdown of substrates, leading to energy production. NADPH, on the other hand, is mainly used in anabolic pathways, like the synthesis of fatty acids or nucleic acids, where it provides the reducing power needed for biosynthesis.
C. Catabolic pathways use a wide variety of substrates to produce a small number of waste products.
- This statement is also incorrect. While it is true that catabolic pathways involve the breakdown of a variety of substrates (e.g., carbohydrates, lipids, proteins), they typically generate a wide variety of waste products (like CO2, ammonia, and urea, among others), depending on the specific pathways and the substrates involved. It is not accurate to say they produce a “small number” of waste products.
D. Catabolic pathways are generally reductive while anabolic pathways are generally oxidative.
- This statement is incorrect. Catabolic pathways are generally oxidative, meaning they involve the loss of electrons (e.g., the breakdown of glucose in glycolysis and the citric acid cycle releases energy and involves oxidation). Anabolic pathways, on the other hand, are generally reductive, meaning they require the addition of electrons (for example, in the synthesis of molecules like fatty acids or proteins, where reducing agents like NADPH are used).
Thus, the correct answer is B, as none of the provided statements are entirely accurate.