Photosynthesis is the process by which plants and some single-celled organisms produce sugars from sunlight and carbon dioxide. These sugars then become the food used in cellular respiration. In plants, photosynthesis occurs in specialized structures known as chloroplasts.
The overall reaction of photosynthesis utilizes six carbon dioxide molecules and six water molecules to produce one sugar molecule (glucose) and six oxygen molecules.
Photosynthetic pigments include chlorophylls, carotenoids and xanthophylls. These pigments are each sensitive to a particular range of light wavelengths.
Eukaryotic cells perform photosynthesis in a specialized, double-membraned structure called the chloroplast. The chloroplast contains a stacked series of membranes known as the thylakoid. Stack of thylakoids are called grana with the intermembrane space between thylakoids called the stroma.
Light Dependent Reactions
When light strikes photosensitive pigments such as chlorophyll, the electrons enter a high energy state. Through a series of electron transports, the energy from these excited electrons is utilized to create adenosine triphosphate (ATP) and nicotine adenine dinucleotide phosphate (NADPH). This process is known as photophosphorylation and occurs in the grana.
Light Independent Reactions
The high energy bonds produced during the light dependent reactions are used to create carbon-carbon bonds from carbon dioxide. This process, sometimes referred to as the Calvin Cycle, involves a multi-step series of enzymatic reactions to create a glucose sugar molecule from the addition of the carbon from a carbon dioxide molecule to a starter molecule called ribulose bisphosphate.