Anyone that has ever been to the grocery store or market to purchase vegetables will testify to the importance of green. Anyone that has ever been in a car waiting at the T- Junction for the green traffic indicator can testify to why it is important to patiently wait for the green light. The whole living is based on greens. Studies have shown that humans can exist by feeding only on greens, no wonder we have vegetarians.
Having known this, a question: “What is the source of green?” is very important.
Don’t go too deep in thought friend. The source of the greens we quest after is in a very small and beautiful organelle called “The chloroplast”.
The chloroplast is a cell organelle found mainly in the alga and plant cells. It is made up of three membrane system:
- The outer membrane system
- The inner membrane system
- The thylakoid membrane system
The outer membrane system
The outer membrane and the inner membrane are separated by a space called intermediate membrane. The outer membrane is permeable to a host of ions and many metabolites unlike the inner membrane that is selectively permeable.
The inner membrane system
The inner membrane is selectively permeable to cell transport proteins such as Sodium-Potassium pump that help to carry Sodium and Potassium ions in and out of the organelle, Sodium-Glucose transport protein that help to carry Sodium ions and sugar across the organelle. The inner membrane encloses a protein fluid called the Stroma which contains a host of enzymes, plastid DNA, RNA and ribosomes. Within the stroma is another membrane called the thylakoid membrane.
The Thylakoid membrane system
The thylakoid membrane is located inside the stroma. It is a network of membrane bound flattened compartments called the thylakoids that are arranged in stack called grana. The grana are interconnected by tubular membrane called integrated lamella. Thylakoids are composed of green pigments called chlorophyll A and B, as well as yellow pigments called the carotenoids.
The number of chloroplasts in different plants varies. In higher plants, the number of chloroplast varies from in cells from 30-200 chloroplasts. Although chloroplasts are usually 4-5ʮm in size. Chloroplasts also differ in shapes: they are cup-shaded in Chlamydomonas, ribbon shaped in Spirogyra, star-shaped in Zygnema and spherical or ovoid-shaped in higher plants.
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