How does carbon become part of organic molecule?

Answer 1

In living organisms, carbon fixation (incorporation of atmospheric inorganic carbon dioxide into organic compounds) is carried out by certain microbes and most plants and the other organisms feed on plants to acquire their organic compounds. The process of carbon fixation is called photosynthesis and it's driven by sun light and catalyzed by enzymes. In organic chemistry labs, chemists have found ways to either create organic molecules from inorganic ones or add carbon onto preexisting organic molecules, though these processes require very strigent reaction conditions that are different from those in living organisms, mostly because we cannot make use of enzymes the same way as living organisms do. The earliest experiments involved reacting carbon dioxide and ammonia by adding an electrical current, making urea as the product. Current organic chemstry techniques have countless ways to manipulate organic compounds and it will be futile to try to list even a fraction of the techniques. Follow the link below for a Wikipedia page that has links to a large number of possible organic chemistry reactions.