Compare the process of photosynthesis and the process of baking a cake

Light reactions take place in the thylakoid membrane. The sunlight here is converted into the ATP and NADPH. The chlorophyll absorbs the light energy and started a chain of reaction that results in the formation of ATP, oxygen, NADPH. Both these molecule are used in dark reaction to make sugar.

The light reactions are similar to the process of baking cake in the oven. The dark reaction takes place in the stroma. Carbon dioxide is changed to sugar by using the energy from the ATP and NADPH. This is known as the Calvin cycle.  

unicellular organisms, like bacteria, are able to perform all life functions within one single cell. multicellular organisms need many different types of cells to carry out the same life processes. each of these special types of cells has a different structure that it perform a specific function.