The process of photosynthesis is commonly written as: 6CO2 + 6H2O → C6H12O6 + 6O2. This means that the reactants, six carbon dioxide molecules and six water molecules, are converted by light energy captured by chlorophyll (implied by the arrow) into a sugar molecule and six oxygen molecules, the products. The sugar is used by the organism, and the oxygen is released as a by-product.
Photosynthesis, derived from the Greek words photo, meaning “light,” and synthesis “putting together,” is a process used by plants and some bacteria to harness the energy from sunlight to convert water and carbon dioxide to produce sugar (glucose) and oxygen
The Photosynthesis Equation
In photosynthesis, solar energy is converted to chemical energy. The chemical energy is stored in the form of glucose (sugar). Carbon dioxide, water, and sunlight are used to produce glucose, oxygen, and water. The chemical equation for this process is:
6CO2 + 12H2O + light → C6H12O6 + 6O2 + 6H2O
Carbon Dioxide + Water + Light yields Glucose + Oxygen
Six molecules of carbon dioxide (6CO2) and twelve molecules of water (12H2O) are consumed in the process, while glucose (C6H12O6), six molecules of oxygen (6O2), and six molecules of water (6H2O) are produced.
This equation may be simplified as: 6CO2 + 6H2O + light → C6H12O6 + 6O2.
What are the Reactants of Photosynthesis?
The reactants for photosynthesis are light energy, water, carbon dioxide and chlorophyll, while the products are glucose (sugar), oxygen and water.
We’ve established that plants need carbon dioxide (CO2) and water (H2O) to produce their food, but where do these reactants come from and how do they get where they need to go inside the plant?
Plants take in carbon dioxide from the air through small openings in their leaves called stomata. Some plants (most monocots) have stomata on both sides of their leaves, and others (dicots and a few monocots) only have stomata on the underside, or lower epidermis.
Plants take in carbon dioxide from the air through small openings in their leaves called stomata.
Plants get water from the soil surrounding their roots, and water gets to the leaves by traveling through the xylem, part of the plant’s vascular system. In leaves, the xylem and phloem are contained in the vascular bundle.
Once inside the leaf, the carbon dioxide and water molecules move into the cells of the mesophyll, the layer of ground tissue between the upper and lower epidermis. Within these cells, organelles called chloroplasts use the carbon dioxide and water to carry out photosynthesis.
Products of Photosynthesis
Did you know that oxygen is actually a waste product of photosynthesis? Although the hydrogen atoms from the water molecules are used in the photosynthesis reactions, the oxygen molecules are released as oxygen gas (O2). (This is good news for organisms like humans and plants that use oxygen to carry out cellular respiration!) Oxygen passes out of the leaves through the stomata.
The light-independent reactions of photosynthesis—also known as the Calvin cycle—use enzymes in the stroma, along with the energy-carrying molecules (ATP and NADPH) from the light-dependent reactions, to break down carbon dioxide molecules (CO2) into a form that is used to build glucose.The mitochondria in the plant’s cells use cellular respiration to break glucose down into a usable form of energy (ATP), which fuels all the plant’s activities.
After the light-independent reactions, glucose is often made into larger sugars like sucrose or carbohydrates like starch or cellulose. Sugars leave the leaf through the phloem and can travel to the roots for storage or to other parts of the plant, where they’re used as energy to fuel the plant’s activities.