Because they are required in minute or very small qantities
Usually cell growth in normal cells are controlled by genes that promotes cell proliferation and also inhibiting them. If a damage occurs in normal cell,the damage is either rectified or apoptosis is initiated. When these genes that control cell proliferation or apoptosis acquires mutations they lose their ability to control their cell division process thereby acquiring uncontrolled cell growth.
Answer:
So...
Explanation:
When a reaction occurs without an enzyme (a catalyst, meaning that it <em>speeds up </em>reactions), the activation energy is much higher than that of a reaction using an ezyme. This is due to the fact enzymes lower the activation energy (energy needed to start a reaction) meaning that there's a higher chance of successful collisons between the active site's of enzymes and substrates - forming enzyme-substrate complexes.
<em>Hope that helps! x</em>
The answer to your question is,
D) a primary mixture of elements
-Mabel <3