The three-carbon carbohydrate that carbon dioxide is first fixed into is:

1. Carbon fixation does not produce glucose directly. 2. After a series of chemical reactions, the carbon from carbon dioxide in the atmosphere is fixed into carbohydrates. 3. Specifically it becomes a three-carbon molecule called glyceraldehyde-3-phosphate, or G3P. 4. Glucose, the primary energy source in cells, is made from two three-carbon G3Ps. _Source: OpenStax Biology for AP(R) Courses (CC BY 4.0), Ch 8 'Photosynthesis', sections 8.1-8.3_