Wize AP Biology Textbook > Photosynthesis
Plant Structures for Photosynthesis
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Plant Structures for Light-Dependent Reactions
The main organelle responsible for the light-dependent reactions of photosynthesis is the chloroplast. It harvests energy light to produce sugar. Chloroplasts are separated into three compartments by three membranes:
- Outer Chloroplast Membrane – Highly permeable.
- Intermembrane Space – Space found between the inner and outer membranes.
- Inner Chloroplast Membrane – Highly impermeable except where specific transporters are present. Impermeable to ATP and NADPH.
- Stroma – The aqueous fluid within the inner chloroplast membrane; analogous to the matrix of mitochondria. Site of sugar production.
- Thylakoid Membrane – Highly folded membrane which forms a set of flattened, disc-like sacs (thylakoids) which are arranged in stacks (grana). Contains chlorophyll, site of electron transport chain, and ATP synthase.
- Thylakoid Space – Internal compartment of thylakoid.
Chlorophyll
- Chlorophyll – Light-capturing pigments found in chloroplast, are responsible for the first step in photosynthesis.
- When pigment absorbs light an electron jumps to a higher energy level; as it returns to its ground state, the released energy is transferred to the neighboring chlorophyll molecule.
- Pigments are organized into antennae complexes that associate with the two photosystems of photosynthesis.
Practice: Light Absorption Location
Where does light absorption occur in plants?
Practice: Plant Structures
The pigment called ___________ present in chloroplasts is able to absorb light from the sun. They are organized in ___________ complexes on the ____________ membrane.