Thylakoid protein phosphorylation in chloroplasts helps regulate the distribution of energy between photosystems during photosynthesis. This process, known as state 1-state 2 transitions, is controlled by the redox state of electron carriers. When plastoquinone is reduced, energy shifts to photosystem I, while oxidation of plastoquinone redirects energy to photosystem II. These transitions are mediated by reversible protein modifications. Additionally, the balance between photosystem I and II can be adjusted over time by changing their quantities. Recent evidence suggests that this adjustment is also influenced by the redox state of electron carriers, affecting protein synthesis and breakdown. This integrated feedback system helps maintain redox balance and quantum yield in photosynthesis.