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This question can be answered on various levels. On the planetary level, most photosynthesis occurs in the oceans, because the oceans occupy the vast majority (70%) of the earth's surface. In terms of organisms, photosynthesis occurs in autotrophes that contain the green pigment chlorophyll.

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Photosynthesis ASU

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Plants Make Their Own Food

Do plants eat? Yes, but not like we do. Instead of going to the kitchen, the local store, or restaurant for a meal, they get food using a process called photosynthesis.

Take a quick look in a dictionary and you will see that "photosynthesis" is made from two words - "photo," meaning light, and "synthesis," which means to make something. Just knowing these root words gives a hint about the way plants get their food. They make it using light.

Made From Light

Like animals, plants need energy to do work. Humans and other animals eat food to get energy. Your day might include cereal for breakfast, a sandwich for lunch and maybe a salad and fish for dinner. These foods and also many of the things we drink give us energy.

Plants don't eat food. They use the energy from the sun, or other light and use it to make their food. The ingredients for this process are water, air, and light. Plants don't use all the parts of the air, they only use the carbon dioxide (CO2) to make their food. They produce oxygen during this process.

Plants use photosynthesis to make sugar. Just like eating sugar gives humans energy to work and play, sugar allows plants to grow and do other important work.

Snacking on Light

Like its name, photosynthesis can be split into two parts. The first part is the light-dependent reactions. In these reactions, plants convert sunlight energy into different forms of energy that are used in the second part of photosynthesis. In the second part, the Calvin cycle, carbon dioxide from the air and the energy from the light-dependent reactions are used to make a sugar called glucose (Greek gleukos = sweet wine).

Where the Work is Done

Inside plant cells there are little factories called chloroplasts. It is inside the chloroplasts where both parts of photosynthesis happen. These little factories also make a pigment that gives plants their green color. The pigment is called chlorophyll. Besides giving leaves and stems their green color, chlorophyll also helps plants soak up sunlight energy.

Do Plants Breathe?

Oxygen, the gas we breathe, is a product of the light-dependent reactions of photosynthesis. We breathe out carbon dioxide, which plants use in photosynthesis. Plants have tiny holes in their leaves called stomata. Stomata open to allow air to enter the leaf so that the plant can get carbon dioxide for photosynthesis.

The open stomata can allow a lot of water to leave the plant through evaporation, so stomata close when too much water exits. Plant cells also use oxygen when they break down sugars for energy in cellular respiration (Latin re = again, and spirare = to breathe). All cells respire, but only plants, algae, and some bacteria also have photosynthesis.

All of the carbon in our bodies came from photosynthesis. Just think about the foods you eat. They come from plants or from animals that eat plants. Our carbon comes from other living things, so we are called consumers or heterotrophs (Greek heteros = other, different, and trophos = feeder). Plants are producers or autotrophs (Greek auto = self, and trophos = feeder), which means that they get carbon from sources that are not living. Carbon dioxide from the air is the specific carbon source for plants, so you could say that plants are made out of "air"!

Images via Wikimedia Commons. Cyanobacteria image by BASF - The Chemical Company.

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If it weren't for plants, most of the other organisms on this planet wouldn't survive. Most plants can use energy from the sun to make their own food.

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The energy cycle for life is fueled by the Sun. The main end product for plants and animals is the production of highly energetic molecules like ATP . These molecules store enough immediately available energy to allow plants and animals to do their necessary work.

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Biology for Kids: Plant Cell Chloroplasts

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Kids learn about plant cell chloroplasts in the science of biology including their function, structure, and how they help make energy through the process of photosynthesis.

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Organisms are divided into autotrophs and heterotrophs according to their energy pathways. Autotrophs are those organisms that are able to make energy-containing organic molecules from inorganic raw material by using basic energy sources such as sunlight. Plants are the prime example of autotrophs, using photosynthesis.

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For the Expert | Games & Puzzles | Vocabulary | Teacher Resources

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What Is Radiant Energy?

Have you ever wondered what the temperature is in outer space? No matter how you express it, it is very cold, even close to the sun. We can explain this phenomenon in terms of energy, which is the ability to do work, and matter, which is anything that has mass and takes up space. Energy does work when it forces something to move. As the particles move faster, the temperature increases. Well, if there's nothing there to move, no work can be done, even if energy is available.

You see, outer space is void of matter. Therefore, the energy from the sun doesn't have anything to warm up. We feel the warmth of the sun as the sun's energy forces our bodies' molecules to move faster - in other words, work harder. Let's explore this concept in more detail.

The energy from the sun is called radiant energy, or energy possessed by vibrating particles. Vibrating particles in the sun create waves that travel through space and time. We call these waves created by vibrating particles electromagnetic waves. Electromagnetic waves contain both electrical and magnetic properties that allow them to travel through space, even though space is void of matter. Other waves, for example, the waves in the ocean, require matter to move.

We can easily demonstrate the formation of waves from vibrating particles. Here - let's do a little experiment. If you've got a cup of coffee, assuming it's cool enough, or a glass of water by you, just stick your finger down in the water and wiggle it - vibrate it - back and forth, and watch the waves form. Now, while these are not electromagnetic waves, the concept is similar to how vibration forms.

How Does Radiant Energy Work?

As we just discussed, electromagnetic waves can travel through outer space. They can travel for long distances, and they move at the speed of light. Work is done by radiant energy as the electromagnetic waves come into contact with particles and cause them to move. Let's examine the sun as a source of radiant energy.

Radiant energy from the sun is specifically referred to as solar energy. The sun contains a tremendous amount of radiant energy that produces electromagnetic waves. These waves travel away from the sun through space and time. When the waves come into contact with some object - let's say our skin - they cause the molecules in our skin to move faster. As the molecules move faster, we feel warmer.

Those same electromagnetic waves traveling through space don't do any work because there isn't anything to contact. At the same time, there is nothing to stop the waves, so they continue to travel until they hit something.

What Are Electromagnetic Waves?

To better understand how radiant energy works, we need to look at electromagnetic waves in a bit more detail. Electromagnetic waves are similar to other waves, like waves in the ocean, in that they have high parts, and they have low parts, and they move. The tops of the waves are called crests, and the bottom of the waves are called troughs. Just as there are different kinds of waves, there are different types of electromagnetic waves.

Each type of electromagnetic wave is defined by its wavelength. Well, what's that? It's simply the distance between the waves. While it is easier to measure the wavelength of waves in the ocean because we can see them, scientists have come up with ways to measure the wavelength of electromagnetic waves, even though we can't see them.

Another way of looking at the different types of waves is by their frequency, which can be thought of as the speed at which the wave moves. Frequency can also be expressed in terms of , or the number of waves formed in a period of time. Waves with long wavelengths have shorter frequencies, while waves with shorter wavelengths have higher frequencies.

What Do Waves Have to Do with Energy?

Okay. So, what do these waves have to do with energy? Let me start off by saying that electromagnetic waves carry energy. Electromagnetic waves with the shorter wavelengths and higher frequencies carry more energy - in other words, they have a greater ability to do work.

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what is radiant energy? - definition & examples - video & lesson transcript | study.com

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What is Radiant Energy? - Definition & Examples - Video & Lesson Transcript | Study.com

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Have you ever wondered what the temperature is in outer space? No matter how you express it, it is very cold, even close to the sun. We can explain this phenomenon in terms of energy, which is the ability to do work, and matter, which is anything that has mass and takes up space.

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What is Photosynthesis?

The word photosynthesis can be separated to make two smaller words:

"photo" which means light

"synthesis" which means putting together

Plants need food but they do not have to wait on people or animals to provide for them. Most plants are able to make their own food whenever they need it. This is done using light and the process is called photosynthesis.

Photosynthesis is the process by which plants make their own food. We will add more details to this definition after making a few things clear as you will see below.

What is needed for Photosynthesis?

To make food, plants need not just one but all of the following:

Let's take a look at how these are collected by plants.

Carbon dioxide from the air passes through small pores (holes) in the leaves. These pores are called stomata.

Water is absorbed by the roots and passes through vessels in the stem on its way to the leaves.

Sunlight is absorbed by a green chemical in the leaves.

What happens during Photosynthesis?

The photosynthesis process takes place in the leaves of plants. The leaves are made up of very small cells. Inside these cells are tiny structures called chloroplasts. Each chloroplast contains a green chemical called chlorophyll which gives leaves their green color.

Chlorophyll absorbs the sun's energy.

It is this energy that is used to split water molecules into hydrogen and oxygen.

Oxygen is released from the leaves into the atmosphere.

Hydrogen and carbon dioxide are used to form glucose or food for plants.

Some of the glucose is used to provide energy for the growth and development of plants while the rest is stored in leaves, roots or fruits for later use by plants.

Here is the process in greater detail:

Photosynthesis occurs in two stages commonly known as Light dependent Reactions and the Calvin Cycle.
Light dependent Reactions
Light dependent reactions occur in the thylakoid membrane of the chloroplasts and take place only when light is available. During these reactions light energy is converted to chemical energy.

Chlorophyll and other pigments absorb energy from sunlight. This energy is transferred to the photosystems responsible for photosynthesis.

Water is used to provide electrons and hydrogen ions but also produces oxygen. Do you remember what happens to the oxygen?

The electrons and hydrogen ions are used to create ATP and NADPH. ATP is an energy storage molecule. NADPH is an electron carrier/donor molecule. Both ATP and NADPH will be used in the next stage of photosynthesis.

Details about the flow of electrons through Photosystem II, b6-f complex, Photosystem I and NADP reductase have not been included here but can be found under The Process of Photosynthesis in Plants.
The Calvin Cycle
The Calvin Cycle reactions occur in the stroma of 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 energy from ATP along with NADPH are used to form glucose.

More details about the formation of sugars can be found under the Process of Photosynthesis in Plants.

What have you learned so far?

You already know that plants need carbon dioxide, water and sunlight to make their food. You also know that the food they make is called glucose. In addition to glucose, plants also produce oxygen. This information can be written in a word equation as shown below.

The equation below is the same as the one above but it shows the chemical formula for carbon dioxide, water, glucose and oxygen.

Now back to the definition... Earlier you learned that photosynthesis is the process by which plants make their own food. Now that we know what plants need to make food, we can add that information as shown below.
Photosynthesis is the process by which plants make their own food using carbon dioxide, water and sunlight.
What does Photosynthesis produce?

Photosynthesis is important because it provides two main things:

Some of the glucose that plants produce during photosynthesis is stored in fruits and roots. This is why we are able to eat carrots, potatoes, apples, water melons and all the others. These foods provide energy for humans and animals.

Oxygen that is produced during photosynthesis is released into the atmosphere. This oxygen is what we breathe and we cannot live without it.

While it is important that photosynthesis provides food and oxygen, its impact on our daily lives is far more extensive. Photosynthesis is so essential to life on earth that most living organisms, including humans, cannot survive without it.

All of our energy for growth, development and physical activity comes from eating food from plants and animals. Animals obtain energy from eating plants. Plants obtain energy from glucose made during photosynthesis.

Our major sources of energy such as natural gas, coal and oil were made millions of years ago from the remains of dead plants and animals which we already know got their energy from photosynthesis.

Photosynthesis is also responsible for balancing oxygen and carbon dioxide levels in the atmosphere. Plants absorb carbon dioxide from the air and release oxygen during the process of photosynthesis.

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The word photosynthesis can be separated to make two smaller words: "photo" which means light "synthesis" which means putting together Plants need food but they do not have to wait on people or animals to provide for them. Most plants are able to make their own food whenever they need it.