What would happen in respiration and photosynthesis if there were no electron carriers available?

Answer 1

The electron carriers NAD+ & FAD (for cellular respiration) and NADPH (for photosynthesis) leverage reduction-oxidation (redox) reactions to convert energy from one form to the other (for respiration it's energy out of glucose into ATP that cells can use, for photosynthesis it's energy out of light into glucose and ATP that the plant cells can use). Without these available, the cells would not be able to generate energy and thus would not survive. They are a crucial for life.