4. What is the stroma of a chloroplast? What happens there?

Stroma, in botany, refers to the colorless fluid surrounding the grana within the chloroplast. Within the stroma are grana (stacks of thylakoid), and the sub-organelles or daughter cells, where photosynthesis is commenced before the chemical changes are completed in the stroma.The stroma is essential for this because not only does it contain the enzymes necessary for carbon fixation, it also manages the chloroplast response to cellular stresses and signaling between various organelles. It plays an important role in both the light-dependent and light-independent reactions of photosynthesis

energy and particles

the answer is lactic acid from anaerobic respiration. the acid in lactic acid is what creates sore and burning muscles. if you think about how acid burns that will give you a clue for questions like this.