The origin of the chloroplast is explained through
Membrane invagination theory
Endosymbiotic theory
Parasitic theory
None of these
Semi-autonomous Organelles: Chloroplast -
Semi-autonomous Organelles: Chloroplast
Chloroplasts are double membrane bound organelles that are present in plant cells and algal cells. These are primarily concerned with the process of photosynthesis.
Structure of the Chloroplast
1. Membranes
The chloroplast is surrounded by a double-layered membrane - an outer and an inner membrane. Each of these membranes is a phospholipid bilayer. The outer membrane is more permeable than the inner membrane. The space between the two membranes is called in the intermembrane space.
2. Stroma/Matrix
It is the jelly-like fluid present interior to the inner membrane. It is made up of water and soluble proteins. It contains DNA, RNA, ribosomes, enzymes etc.
3. Thylakoids
These are flattened membrane system present in the stroma. These are stacked to form granum (pl. grana) in higher plants. Grana are connected to each other through a stretch of thylakoid called stroma lamellae. These membranes possess photosynthetic pigments coupling factors that perform ATP synthesis.
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The presence of mitochondria and chloroplast as the semi-autonomous organelles within the eukaryotic cell is explained through the endosymbiotic theory.