Photosynthesis and Energy Conversion
From Light to Sugars
Photosynthetic overview
Photosynthesis converts light energy into chemical energy in chloroplasts. The light reactions produce ATP and NADPH, and the Calvin cycle uses them to fix into carbohydrates.
Two-stage logic
Light reactions capture energy; the Calvin cycle uses that energy to build organic molecules.
Thylakoids and electron flow
In the thylakoid membrane, photons excite chlorophyll electrons. Water is split to replace lost electrons, releasing . Electron transport builds a proton gradient that powers ATP synthase.
What is the immediate source of the oxygen released during photosynthesis?
The oxygen comes from the splitting of water in the light reactions.
Correct answer: Water
What is the main product of the Calvin cycle that can be used to build glucose?
The Calvin cycle produces G3P, which can be converted into glucose and other carbohydrates.
Correct answer: G3P (glyceraldehyde-3-phosphate)
Photosynthesis vs respiration
Photosynthesis
- Stores energy in sugars
- Uses light energy
- Common in chloroplasts
Respiration
- Releases energy from sugars
- Uses electrons to make ATP
- Common in mitochondria
The Calvin cycle directly depends on which molecules from the light reactions?
ATP provides energy and NADPH provides reducing power for carbon fixation.
Correct answer: ATP and NADPH