Campbell Biology Concepts & Connections Practice Test 2026 – Complete Prep Guide

The immediate products of CO2 fixation by Rubisco are two molecules of 3-phosphoglycerate. In this step, Rubisco carboxylates the five-carbon RuBP, forming a six-carbon intermediate that quickly splits into two 3-carbon molecules, 3-PGA. This is the first product of the Calvin cycle’s carbon fixation phase. NADPH is used later in the reduction of 3-PGA to glyceraldehyde-3-phosphate, RuBP is the substrate Rubisco acts on, and glucose is produced only after multiple subsequent steps from G3P.