Photosynthesis and the Secret Food Factory

Contributor: Jay Gregorio. Lesson ID: 13380

Plants are the only living organisms that can make their own food. How do they do it? Why is it so important to every organism on the planet? Let's explore!


Life Science

learning style
Auditory, Visual
personality style
Grade Level
Middle School (6-8), High School (9-12)
Lesson Type
Dig Deeper

Lesson Plan - Get It!

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When you are hungry, you find something to eat from your pantry or the fridge. When animals get hungry, they eat other animals, plants, or both depending on their diet.

  • What about plants?
  • How do they get food?

plant in sunshine

By now, you have learned that plants need water, sunlight, and soil in order to survive. Interestingly, these things are not considered food. Plants use them, however, to make their own food!

The ability to make their own food is a characteristic unique to plants. Keep reading to learn more about their food-making process and the other essential elements that support their growth!

So much is happening in nature right at this moment, like flowers blooming, oranges ripening on branches, and tree roots spreading through the ground. The one common element that makes all this growth possible is photosynthesis.

flower sprouting

What Is Photosynthesis?

The word photosynthesis can be broken down into two parts. The first word photo means light, and the second word synthesis means putting things together.

Photosynthesis, therefore, must mean putting things together through light. It is the process used by plants, algae, and certain bacteria to harness energy from sunlight and turn it into chemical energy.

More simply, photosynthesis is the process by which plants make their own food.

Photosynthesis is one of the most important processes in nature. Without it, there would be no plants on the earth. Without plants, animals that need them to survive would not exist. And without those animals, the rest of the food chain would collapse as well.

In fact, the very oxygen that we breathe to survive comes from plants.

  • What do plants need in order to photosynthesize their food?

Photosynthesis requires three elements.

  1. Carbon dioxide that is present in the atmosphere passes through the small pores called stomata in plant leaves.
  2. Water is absorbed through the roots and transported to the stem, small branches, and leaves.
  3. Sunlight is absorbed by the green chemical called chlorophyll on the leaves.

Sounds simple enough; however, the actual process within plants is fascinating.

  • Are you ready to unravel what goes on inside this secret food factory?

The Secret Food Factory

There are two phases to photosynthesis.

First Phase: Absorption and Splitting

During this phase, the chloroplasts inside the tiny cells of the leaves absorb the sun's energy, which is stored in the chemical called ATP. An electron carrier or donor molecule called NADPH is also created.

The energy absorbed is used to split water molecules apart into hydrogen and oxygen atoms. The oxygen then leaves the plants through its leaves.

Second Phase: Glucose Production

The carbon dioxide that enters the leaves from the atmosphere combines with the remaining hydrogen to form a sugar called glucose. This is the plant's food.

This sugar production process uses ATP and, therefore, does not require sunlight so it can happen at night, unlike the first phase.

photosynthesis diagram

The second phase is called the Calvin Cycle because it was first described by scientist Melvin Calvin.

The Calvin Cycle reactions occur in the stroma, a liquid inside the chloroplasts. Although these reactions can take place without light, the process requires ATP and NADPH, which were created using light in the first stage.

Carbon dioxide and the energy from ATP, along with NADPH, are used to form glucose.

While all plants need sunlight and water to survive, the amount of each varies from one species of plant to another. Plants like cacti survive in the desert because they have the ability to store fluid within. Other plants can live indoors because they don't require direct sunlight.

Knowing these things will help you understand their characteristics, identify their best planting location, and maximize their growth.

Watch the video below to learn more.

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Why Is Photosynthesis Important to Us?

Obviously, photosynthesis is important for plants because it is the foundation for their growth and development. It is also important for humans because it provides two things we need -- energy and oxygen!

Fruits and vegetables are a part of our diet. Some of the sugar or glucose produced by plants is stored within them and, therefore, provides us with energy when we ingest them. We then use this energy to grow and develop.

The benefits from the energy stored within plants is even more extensive than that. Think about fossil fuels such as coal, natural gas, and oil. These fuels were made from the remains of plants and animals that existed on this planet long ago -- its energy trapped and waiting to be harvested.

Our atmosphere requires a balance in the amount of carbon dioxide and oxygen in the air. Plants absorb carbon dioxide and release oxygen during photosynthesis.

This oxygen gas is what humans and animals need to breathe and survive. Without oxygen, your body would not be able to burn sugars and fatty acids to produce energy.

You see, everything in nature serves a purpose. It is a beautifully designed mechanism that happens even without us knowing or paying attention to it.

Keep going in the Got It? section to test your knowledge of photosynthesis and see how much you learned!

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