Describe the overall changes in matter that occur during the light-independent reactions. What does the plant start with and what does it end with? What is the source of energy that powers this change? (Please keep it as simple as you can)

In the light-independent reactions, the plant starts with carbon dioxide and ends up with glyceraldehyde-3-phosphate (G3P). It uses ATP and NADPH from the light-dependent reactions as energy sources  

Explanation:

Step 1: CO₂ adds to ribulose biphosphate (RBP) to form a six-carbon sugar that immediately decomposes into two molecules of 3-phosphopglycerate (3-PGA).

CO₂ + RBP ⟶ 2 3-PGA

Step 2. A phosphate group adds to the 3-PGA to form 1,3-biphosphoglycerate (1,3-BPG).

3-PGA + ATP ⟶ 1,3-BPG + ADP

Step 3. NADPH reduces the 1,3-BPG to G3P

1,3-BPG + NADPH ⟶ G3P + NADP⁺

Most of the G3P is regenerated into RBP, but some leaves the cycle to become glucose.

There are three phases to the light-independent reactions, collectively called the Calvin cycle: carbon fixation, reduction reactions, and ribulose 1,5-bisphosphate (RuBP) regeneration. Though it is called the "dark reaction", the Calvin cycle does not actually occur in the dark or during nighttime.

The light-independent reactions use the ATP and NADPH from the light-dependent reactions to reduce carbon dioxide and convert the energy to the chemical bond energy in carbohydrates such as glucose.