Photosynthesis begins when pigments capture light energy. Understanding what light is and how pigments absorb it explains why plants appear green and how photosynthetic organisms gather energy from their surroundings.
The sun emits electromagnetic radiation, a form of energy that travels as waves. The full range of possible wavelengths is called the electromagnetic spectrum. Visible light is only a small part of that spectrum—the portion humans can see.
All flashcards
What is wavelength?
Wavelength is the distance between corresponding points on consecutive waves, such as from one crest to the next.
What is the electromagnetic spectrum?
It is the range of all possible wavelengths of electromagnetic radiation, including visible light, UV rays, and X-rays.
Why does chlorophyll a appear green?
Chlorophyll a absorbs blue and red wavelengths relatively well but reflects much of the green light, which is the color people see.
What is an absorption spectrum?
It is the particular pattern of wavelengths absorbed by a pigment.
Why are multiple pigment types useful?
Because different pigments absorb different wavelengths, their combined absorption can let an organism capture light across a wider range.
Quiz questions
In organisms with two photosystems, what happens to an electron after light first excites it in photosystem II?Answer: It passes through an electron transport chain toward photosystem I.
As electrons move through the electron transport chain, how is their energy used?Answer: It powers pumps that move hydrogen ions from the stroma into the thylakoid space.
What describes chemiosmosis during the light-dependent reactions?Answer: Hydrogen ions flow down their gradient through ATP synthase.
What is photophosphorylation?Answer: ATP formation during the light-dependent reactions.
How does photosystem I contribute to NADPH formation?Answer: Light re-energizes electrons that help convert NADP+ to NADPH.
Based on Concepts of Biology by Samantha Fowler, Rebecca Roush, James Wise (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.