while the electron transport chains of photosynthesis are ..

Keep in mind, water is the source of the electrons. As shown in this figure, electrons are removed from water in photosystem II, and consequently, these electrons become energized into a more energetic state. Protons and oxygen are released as by-products of this reaction.
The electron transport chain of respiration occurs in the mitochondria, whereas the electron transport chains of photosynthesis are located in the chloroplasts. The thylakoid membrane is home to the many proteins involved.

Describe the role of electron transport chains in the lightdependent reactions of photosynthesis.

The various pigments each absorb light of a different wavelength , and they send this energy to a specialized chlorophyll molecule at the center of the photosystem (the reaction center). The chlorophyll molecules of photosystem I and photosystem II are different but both play an important role in the electron transport chains of photosynthesis.

Electron transport chain - Wikipedia

The majority of life on Earth could not exist without photosynthesis. Recall from the section on that during photosynthesis light energy is converted to chemical energy. Specifically, it is the process whereby plants, protists, and some bacteria use light, water, and carbon dioxide to make sugars. Photosynthesis is not the exact opposite of cellular respiration, but rather a separate process that just so happens to contain many similar features (e.g., the electron transport chain).