The Role of Photosynthesis in the Life of Plants

Instructor: David Wood

David has taught Honors Physics, AP Physics, IB Physics and general science courses. He has a Masters in Education, and a Bachelors in Physics.

How do green plants work? Learn about the process of photosynthesis and how it is vital to keep plants alive and functioning. Discover how the glucose produced in photosynthesis is used by plants.

What Is Photosynthesis?

Have you ever walked through a forest and wondered how the trees and plants around you work? Just as humans have various vital elements to how they work--notably, the need for air, water, food, and the processes that turn those things into molecules we need--plants also have vital elements and processes.

One of the most important processes that allows plants to live is called photosynthesis. Photosynthesis is a process through which green plants create energy using carbon dioxide and water. The process requires a chemical called chlorophyll, which gives plants their green color and allows them to absorb light.

Chlorophyll is necessary for photosynthesis and makes leaves green.
Chlorophyll is necessary for photosynthesis, and makes leaves green

Photosynthesis is a chemical reaction like any other, so we can describe it using a chemical reaction equation. A chemical equation shows what the reaction requires on the left, followed by an arrow, and then the things that the reaction produces on the right. If non-chemicals are needed, then they're written above the arrow. The chemical equation for photosynthesis looks like this:

Photosynthesis equation
Photosynthesis equation

Essentially, this equation tells us that plants use carbon dioxide and water, plus energy from the sun, to produce sugar (the energy the plant needs) and oxygen (which is released into the air). The reactants (what you start with) are on the left, and the products (what you end up with) are on the right. But why is photosynthesis so important to the life of plants? Let's take a look in more detail.

Importance of Photosynthesis for Plants

We know that animals and plants need energy to live. That energy is usually in the form of sugars like glucose. But why do these things need energy? What is it about this energy that allows us to live?

Well, the bodies of animals and plants are always producing cells, which make up living tissues. Cells don't last forever--they are continually dying and need to be replaced. Cells are made up of molecules, some of them quite complex with lots of atoms. Two common categories of molecules found in plants are

cellulose, which help strengthen cell walls, and proteins, like enzymes and chlorophyll. The energy (or glucose) that is produced in photosynthesis contains some of the atoms that are used to build these molecules. But there's more to building molecules than just photosynthesis--plants also need mineral nutrients absorbed from the soil, including nitrates.

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