You are likely to see a connotation used in both advertisement and also some university lectures. If only one answer is permitted, B is the best answer.
When old red blood cells rupture, the released hemoglobin is ingested by macrophages
Answer: The answer is B: The enzyme's active site binds to and stabilizes the transition state, which decreases the activation energy of the reaction.
Explanation: An enzyme is a biological molecule which speeds up the rate of chemical reactions in the body (reactions within cells). They are proteins.
The transition state is the transition from substrate to product. The molecule is no longer a substrate but also not yet a product.
The enzyme is able to speed up the reaction by stabilizing the transition state. The transition state's energy is also the activation energy in terms of reaction. The activation energy is the minimum energy that is required to break some bonds of the reactants in order to turn them to products.
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Fossils only form if certain qualifications are met, and some organisms cannot meet them, so they just cease to exist, not a single sign of them. This could happen if they were organisms that decayed completely. Fossilization can include freezing, drying, and encasement, usually in tar or resin.