Chloroplast of higher plants
Distribution:
- Generally found in all photosynthesizing cells of higher plants.
- Abundant in mesophyll cells, especially palisade mesophyll cells.
Structure:
- Chloroplast exists in various shapes. The common shape is lense shape.
- General size: 5μm (width); 8-10μm (length).
- The fluid matrix of chloroplast is called stroma. The main structure embedded in the stroma are grana (singular = granum) and intergranal lamellae.
- Granum is a stack of thylakoids. A typical chloroplast contains about 40 to 60 grana.
- Neighboring grana are linked by intergranal lamellae.
- Chlorophyll molecules are embedded in thylakoid membranes in groups called photosystems. A photosystem usually consists of about 300 chlorophyll molecules.
- Also embedded in the thylakoid are ATPase enzymes that catalyze ATP synthesis during photosynthesis.
- Stroma also contains starch granules (temporary storage only), DNA, lipid globules and ribosome (70S) and enzymes catalyzing dark reactions.
Structure of Chloroplast
Functions:
- Carry out photosynthesis.
- Temporary storage site for photosynthesis products such as starch.
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