Thylakoid

Definition

A thylakoid is a membrane-bound compartment inside chloroplasts and cyanobacteria where the light-dependent reactions of photosynthesis occur. It contains chlorophyll and other pigments that capture light energy.

5 Must Know Facts For Your Next Test

1. Thylakoids are organized into stacks called grana within the chloroplasts.
2. The thylakoid membrane houses the photosystems, electron transport chain, and ATP synthase.
3. Light absorption by chlorophyll in the thylakoid membrane initiates the process of converting light energy into chemical energy.
4. The interior of a thylakoid is called the lumen, which plays a crucial role in proton accumulation during photosynthesis.
5. Thylakoids are unique to phototrophic eukaryotes like plants and algae as well as some bacteria like cyanobacteria.

Review Questions

• What is the primary function of thylakoids in photosynthesis?
• How are thylakoids structured within chloroplasts?
• What role does the thylakoid lumen play in the light-dependent reactions?

Related terms

Chloroplast: An organelle found in plant cells and algae that conducts photosynthesis.

Photosystem:

A complex of proteins and pigments in the thylakoid membrane that initiates the light-dependent reactions.

Electron Transport Chain:

A series of protein complexes in the thylakoid membrane involved in transferring electrons during photosynthesis.