Light-harvesting complex

Definition

A light-harvesting complex is a group of proteins and pigments that capture and transfer light energy to the reaction center in photosynthetic organisms. This complex is crucial for converting solar energy into chemical energy during photosynthesis, as it facilitates the absorption of light, particularly in chlorophyll molecules, and channels that energy for use in the synthesis of organic molecules.

5 Must Know Facts For Your Next Test

1. Light-harvesting complexes are primarily located in the thylakoid membranes of chloroplasts, where they absorb light energy.
2. These complexes consist of multiple pigments, including chlorophyll a, chlorophyll b, and carotenoids, each playing a role in capturing different wavelengths of light.
3. The absorbed light energy is transferred to the reaction center, where it triggers a series of reactions that lead to the production of ATP and NADPH.
4. Different types of light-harvesting complexes exist, such as those found in plants (LHCs) and those found in cyanobacteria (phycobilisomes), highlighting their evolutionary diversity.
5. The efficiency of light absorption by these complexes is crucial for maximizing photosynthetic output, impacting overall plant growth and productivity.

Review Questions

• How do light-harvesting complexes contribute to the overall efficiency of photosynthesis?
  • Light-harvesting complexes enhance the efficiency of photosynthesis by optimizing the capture of light energy across various wavelengths. They contain multiple pigments that can absorb different parts of the light spectrum, allowing them to maximize energy capture. This captured energy is then transferred to the reaction center, where it is used to drive the conversion of solar energy into chemical forms like ATP and NADPH, which are essential for synthesizing organic molecules.
• Compare and contrast the structure and function of light-harvesting complexes found in plants and cyanobacteria.
  • Light-harvesting complexes in plants are typically composed of chlorophyll a, chlorophyll b, and carotenoids, organized around a core protein structure. In contrast, cyanobacteria possess phycobilisomes as their light-harvesting structures, which contain phycobilin pigments that allow them to capture a wider range of light wavelengths. While both types serve the primary function of capturing light energy for photosynthesis, their structural differences reflect adaptations to their respective environments and evolutionary paths.
• Evaluate the role of light-harvesting complexes in ecological systems and their impact on global carbon cycles.
  • Light-harvesting complexes play a fundamental role in ecological systems by facilitating photosynthesis, which is essential for converting solar energy into chemical energy stored in organic molecules. This process not only supports plant growth but also forms the base of food webs, sustaining herbivores and higher trophic levels. Furthermore, by capturing carbon dioxide during photosynthesis and producing oxygen as a byproduct, these complexes are vital for regulating atmospheric CO2 levels and contributing to the global carbon cycle. Thus, they are key players in maintaining ecosystem balance and combating climate change.

Related terms

Photosystem:

A protein-pigment complex found in thylakoid membranes that plays a key role in photosynthesis by capturing light energy and driving the conversion of water and carbon dioxide into glucose.

Chlorophyll:

The green pigment found in plants, algae, and cyanobacteria that absorbs light energy, primarily in the blue and red wavelengths, playing a vital role in photosynthesis.

Electron Transport Chain: A series of protein complexes located in the thylakoid membrane that transfer electrons from water to NADP+, generating ATP and NADPH as part of the light-dependent reactions of photosynthesis.