Question

2. Structure and Function of Chloroplast

Where do protons accumalate?

Where is Chlorophyll found?

In which part of the the chloroplast are carbohydrates made?

Answer 1

Chloroplast are organelles found in the cells of plants and green algae.

Structure of Chloroplast - They are round or oval shaped, 1-2 micrometer thick and 5-7 micrometer in diameter. It has an inner and outer membrane with an intermediate space in between the two. The inner membrane surrounds the grana and the stroma. Stacks of thylakoids are called grana, and the inner dense fluid or matrix is called the stroma.

Function of Chloroplast - In general terms, they are the food producers. They convert light energy from the sun to chemical energy in the form of food (Carbon dioxide in the presence of sunlight and water is converted to glucose and oxygen) by the process called photosynthesis. This process depends on the pigment Chlorophyll.

Chlorophyll pigment is found in the thylakoid sacs of the chloroplast.

The whole process of photosythesis has mainly two steps - Photosynthetic electron transfer reaction and carbon fixation reaction. Photosynthetic electron transfer uses photon from sunlight to help the electron transfer from water to NADP⁺ in the thylakoid membrane, and the energy is stored as electrochemical gradient of protons. In chloroplasts, protons accumulate in thylakoid lumen. This proton gradient helps the synthesis of ATP in the stroma. The electrons then combine with NADP⁺ to form NADPH. In carbon fixation, ATP and NADPH produced help the conversion of carbondioxide into carbohydrates. The fixation process occurs in the chloroplast stroma and results in the production of glucose (carbohydrate).