Describe the process of photosynthesis, starting with the chloroplast in the leaves
absorbing sunlight.

Chloroplasts reside in most leaf cells. Both chloroplasts and the leaves themselves are different shades of green due to a lovely pigment they contain. A pigment is a compound that absorbs a particular wavelength of visible light. Chlorophyll is a green pigment contained in thylakoid membranes of chloroplasts that is used in photosynthesis by plants. In bacteria that also perform photosynthesis, chlorophylls are in the plasma membrane.

So you might be wondering, how does a pigment absorb light to fuel photosynthesis? First, we need to talk about light itself. The electromagnetic spectrum is the range of wavelengths from the radio waves of your car stereo to high-energy gamma rays. Chlorophyll and other pigments absorb specific visible wavelengths of the electromagnetic spectrum.  

The visible light is literally the colored wavelengths that are visible to your eyes. They range from red, at a wavelength of 700 nm, to blue, at a wavelength of 400 nm. Shorter wavelengths have higher energy (such as blue), and longer wavelengths (like red) have lower energy.  

Chlorophyll mostly absorbs blue and red wavelengths from sunlight. Therefore, it reflects the middle part of this visible spectrum, the green wavelengths.    

This is why plants look green to us. The color of a pigment is the wavelength of light that is reflected, or the wavelength that is not absorbed.

Chlorophyll contains electrons that are normally at a low energy state, or ground state. But when chlorophyll absorbs light energy, the electrons get really excited. Literally! They jump to a high energy level, or excited state. Although we'll save the details of this process for other lessons, this super-excited electron is then transferred from the chlorophyll pigment to a primary electron acceptor. Hence, chlorophyll becomes oxidized.  

Photosynthesis can use both chlorophyll pigments and other accessory pigments that reflect colors other than green. These accessory pigments aren't exactly the jewelry-type accessories of photosynthesis, but they are as helpful as the right pair of shoes to complete an outfit. These accessory pigments absorb other wavelengths of light and pass on energy to chlorophyll, expanding the range of wavelengths that can be used for photosynthesis.