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Why Do Plant Cells Have Chloroplasts & Chlorophyll?

At the basis of all living things on the planet are cells: microscopic pieces of matter that contain all the parts required to make a living thing do its job. The cellular structures of animals and plants are radically different because they perform diverse functions. Two of the more important, and most confused, parts of plant cells are chloroplasts and chlorophyll.

Chloroplasts
- Chloroplasts are elongated discs found in plant cells. Chloroplasts are made up of grana. Grana are stacked disks of thylakoids connected through lamellae, and secured within three layers of protective membrane and suspended in a liquid called stroma. The lamella operates as the skeleton of the chloroplasts, holding the membranes surrounding it together. It also makes sure the stacks do not get too close together, which increases the efficiency of the chloroplast. Chloroplasts house the chlorophyll in the plant cell.
Chlorophyll
- Chlorophyll is the green pigment found inside chloroplasts that processes sunlight in plant cells. It is magnesium based, responsible for photosynthesis and is attached to the outside of all thylakoids. They absorb the blue and red sections of the electromagnetic spectrum best, which is what gives plants a green pigment. The green pigment of the chlorophyll is so strong that food manufacturers and chefs use it to turn food and drinks green.
Purpose
- The process of photosynthesis, by which plants absorb sunlight and convert it into sugar and carbon dioxide, is what allows a plant to grow. It is the chloroplast that absorbs the sun's energy and chlorophyll that turns it into the food. In plants, the food is glucose, as simple sugar made up of carbon, hydrogen and oxygen. The glucose is then broken down by the mitochondria, which can be compared to the digestive system in humans, and transferred to other parts of the cell as energy. It is arguably the most important process for plants in the same way that eating food is for humans. Both chloroplasts and chlorophyll are central to this conversion process.
Need for Both
- It is chlorophyll that is actually responsible for photosynthesis, so in theory, the plant cell does not need both, but without chloroplasts, chlorophyll would be unprotected and unable to collect the sunlight. In the same way cells need a cell wall and animals need skin, chlorophyll needs chloroplasts to protect it -- allowing it to do the job of photosynthesis.

Nature