Question

-!!! Three Medal Question !!!

- Describe the chloroplast and its role in photosynthesis.

- Summarize what happens during the light reactions of photosynthesis.

What happens during the carbon fixation step of the Calvin cycle?

Answer 1

The chloroplast is a large, complex double membraned organelle that performs the function of photosynthesis within plant cells and contains the substance chlorophyll that is essential for this process. All reactions of photosynthesis occur in this organelle, and in addition, the chloroplasts also create sugar from the sun for the cell and make all the food for other organelles. The chloroplasts use photosynthetic chlorophyll pigment and take in sunlight, water and carbon dioxide to produce glucose and oxygen. This is the process of photosynthesis. The organelle takes in minerals found in the soil and air around them, and provides the cell with sunlight to make substances that the cell can process. An important structure in the chlorplasts is the inter-connected, flattened, membranous sacs called thylakoids. These structures are the site of the photosynthetic light reactions and it involves the transfer of electrons from a photo-excited state via the chlorophyll inside the thylakoids membrane to the stroma, which then produces ATP. In addition, the chloroplasts have their own DNA and ribosomes and reproduce by splitting in half, so basically, they are their own individual mini-cells. There are many chloroplasts in each cell to perform photosynthesis and its structure has two membranes. The outer membrane is eukaryotic in origin whereas, the inner membrane believed to be prokaryotic.

Relationship with Other Organelles

The chloroplasts do not work with any cells to a large extent, as they are able to almost function independently. However, mitochondria and chloroplasts are very similar organelles, although the chloroplasts have a more complicated membrane and the mitochondria extract energy from food molecules, whereas chloroplasts capture solar energy.
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