The body obtains vitamin A in two ways. One is by manufacturing it from carotene, a vitamin precursor found in such vegetables as carrots, broccoli, squash, spinach, kale, and sweet potatoes.The other is by absorbing ready-made vitamin A from plant-eating organisms.he body obtains vitamin A in two ways. One is by manufacturing it from carotene, a vitamin precursor found in such vegetables as carrots, broccoli, squash, spinach, kale, and sweet potatoes.
A catalyst is like adding a bit of magic to a chemical reaction. Reactions need a certain amount of energy in order to happen. If they don't have it, oh well, the reaction probably can't happen. A catalyst lowers the amount of energy needed so that a reaction can happen more easily. A catalyst is all about energy.
When less energy is needed for the reaction, more molecules will possess enough energy to get over the barrier. Reducing the barrier is the job of catalysts. They alter the situation to reduce the barrier to reaction. Enzymes are a subset of catalysts; they work on biological reactions.