To determine what must be true of the actual reaction but is not shown in the model, we can analyze each choice based on the principles of conservation of mass and the nature of chemical reactions.
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A. The number of glucose molecules at the beginning of the reaction must equal the number of palmitic acid molecules at the end of the reaction.
This statement is not necessarily true because glucose is converted through a series of reactions to produce other molecules (like palmitic acid), and the stoichiometry may not be one-to-one. -
B. The number of oxygen atoms in the glucose and oxygen must equal the number of oxygen atoms in the palmitic acid, water, and carbon dioxide.
This statement is true because of the law of conservation of mass; the total number of atoms must remain constant throughout the reaction. -
C. Every glucose molecule joins with another glucose molecule to form a molecule of palmitic acid.
This statement is not accurate in the context of the pathway that produces palmitic acid. Palmitic acid synthesis typically involves acetyl-CoA derived from carbohydrates but does not imply that glucose molecules combine directly. -
D. Every carbon atom from the glucose molecule must end up in a molecule of palmitic acid.
This is not true because not all carbon atoms from glucose are necessarily incorporated into palmitic acid; some may be released as CO2 during the process.
Given these analyses, the most accurate statement that reflects the conservation of atoms and is true about the actual reaction is:
B. The number of oxygen atoms in the glucose and oxygen must equal the number of oxygen atoms in the palmitic acid, water, and carbon dioxide.