Cell biologyLesson 2 of 3 in the course Photosynthesis

Photosynthetic Light Capture, Electron Transport, and ATP Synthesis

5 flashcards · 5 quiz questions · 5 match pairs · 4 fill-in sentences · English

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Summary

Photosynthesis begins when pigments capture light energy. This lesson explains how light wavelengths differ, how pigments absorb and reflect light, and why plants use several pigment types.

The sun emits electromagnetic radiation across a broad range of wavelengths, from high-energy gamma rays and X-rays to long-wavelength radio waves. The full range is called the electromagnetic spectrum. Humans see only a small portion of it: visible light.

All flashcards

Photosystem
A thylakoid-membrane protein complex containing antenna pigments and a reaction center.
Photoact
The light-triggered transfer of an electron from reaction-center chlorophyll to a primary electron acceptor.
Photolysis
The splitting of water at photosystem II, supplying replacement electrons and releasing oxygen.
Chemiosmosis
The movement of ions down a gradient through a membrane-associated protein, driving cellular work.
Electrochemical gradient
A difference in ion concentration and electrical charge across a membrane.

Quiz questions

  1. In the light-dependent reactions, which sequence describes electron movement from photosystem II toward NADP+?Answer: PSII, electron carriers, PSI, then NADP+
  2. Why is photosystem II numbered II even though electrons pass through it before photosystem I?Answer: The photosystems were numbered in the order they were discovered.
  3. What happens when photosystem II replaces an electron lost by its reaction center?Answer: Water is split, supplying electrons and releasing oxygen.
  4. Which event directly provides energy for ATP synthase to make ATP in chloroplasts?Answer: Hydrogen ions flow from the thylakoid lumen toward the stroma through ATP synthase.
  5. At which photosystem are electrons re-energized before they help reduce NADP+?Answer: Photosystem I, whose reaction-center pair is P700

Based on Biology 2e by Mary Ann Clark, Matthew Douglas, Jung Choi (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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