Photon

Definition

A photon is a quantum of electromagnetic radiation, essentially a packet of light energy. It has no mass and travels at the speed of light.

5 Must Know Facts For Your Next Test

1. Photons are absorbed by chlorophyll molecules in the thylakoid membranes during the light-dependent reactions.
2. The energy carried by photons is used to split water molecules into oxygen, protons, and electrons in a process called photolysis.
3. Different pigments absorb photons at different wavelengths, facilitating various parts of photosynthesis.
4. Excited electrons from photon absorption drive the production of ATP and NADPH, essential for the Calvin cycle.
5. Photons initiate the electron transport chain in photosystem II by exciting chlorophyll electrons.

Review Questions

• What role do photons play in the light-dependent reactions of photosynthesis?
• How does photon absorption lead to ATP and NADPH formation?
• Why is it important that different pigments absorb photons at different wavelengths?

Related terms

Chlorophyll:

The primary pigment in plants that absorbs light most efficiently at specific wavelengths for photosynthesis.

Thylakoid Membrane: The site within chloroplasts where the light-dependent reactions occur.

Photosystem II: A protein complex in the thylakoid membrane that uses photons to excite electrons, starting the electron transport chain.