Apply as a tutor to teach students online from anywhere in the world.


Apply as a tutor to teach students online from anywhere in the world.


The Reactants and Process of Photosynthesis

The Reactants and Process of Photosynthesis

All living beings need food in order to survive. Some organisms eat others to consume their food, and these are known as heterotrophs like humans and some animals. On the other hand, some living organisms like plants have to make their own food, and hence these organisms are referred to as autotrophs.

Let’s talk in detail about what photosynthesis is and how the process works.


Photosynthesis is the process by which organisms make up their own food by turning light from the sun into chemical energy, which is used as food. Many organisms make their foods through this process, including plants, algae and some particular types of bacteria.

Plants take in water and carbon dioxide through the soil and air. After receiving these essential components, plants turn them into glucose and oxygen, which are utilized by the plants as food.

When we are talking about photosynthesis in plants, there comes a certain chemical equation that is used to describe the process of photosynthesis.

An equation tends to describe how the chemical reaction went by when certain reactants were added to it and what products were produced as a result.

If we talk about a general chemical reaction, then this is the basic equation that explains the basic reaction.

Chemical reactants —-> Final products

Whenever we talk about a certain chemical reaction, there will be certain factors that will be used as the reactants in the process, just like we use ingredients while cooking something and similarly when the ingredients are mixed up and cooked well. This prepares up the product just like the final product in a chemical reaction.

In the process of photosynthesis, we talked about sunlight, carbon dioxide and water as the reactants or the ingredients that are used by plants in order to create the final product that is glucose and oxygen.


Let’s take a look at how these reactants come together to form up the food for living organisms:

Sunlight + Carbon dioxide + Water  ———–> glucose + oxygen

                     6 (CO2)               6(H20)                C6H12O6       6O2

The above equation states how plants produce glucose and oxygen by bringing together sunlight, carbon dioxide and water as chemical reactants. It also tells about the number of reactants and products involved in the process.

When 6 molecules of carbon dioxide and six molecules of water come in contact with sunlight, then the resulting products are a molecule of glucose with 6 molecules of oxygen.

The origin of reactants

Now that we know which reactants are involved in the process of photosynthesis, now let’s talk about how and from where these reactants come from for the plants to utilize.

Carbon dioxide and water are two main reactants involved in the process of photosynthesis. Plants utilize carbon dioxide after receiving it from the air. There are stomata present on the surface of plant leaves. Some plants have stomata on both sides of leaves, while some only have a single side stoma. This part of the plant leaf helps it to utilize carbon dioxide from the air.

On the other hand, when a plant needs water, it gets it from the soil it is present in. the soil below the plant has water flowing.

Plants contain vascular bundles which have xylem and phloem in them. The xylem and phloem are responsible for taking up water and food for the plants, respectively.

In this way, the xylem is responsible for taking up the water from the soil to the plant body in order for the plant to use the water for the process of photosynthesis.

On the other hand, light is required as well for the two elements to be properly used for the photosynthesis process. Plants have specialized cells that contain different pigments. These pigments are responsible for absorbing different colors of lights with different wavelengths. The most common pigment is chlorophyll. Chlorophyll is known to send back the green light coming in, but it absorbs other lights like red and blue from the sun.

During these reactions, high-energy molecules are produced. These molecules include NADPH and ADP. Water molecules are broken down, which further leads to the formation of these high-energy molecules.


Usage of final products

Since the final products produced during photosynthesis are oxygen and glucose, both of them serve different purposes for the plants. Oxygen comes from the breakdown of water molecules. The hydrogen molecules are utilized in the process for high-energy molecules, but the oxygen is a waste product. It is released in the form of a waste product as oxygen gas.

The oxygen that is released as a waste product by the plants is actually utilized by other organisms like humans and animals, who require oxygen from the air for the process of respiration.

Factors limiting photosynthesis

The process of photosynthesis is a controlled process that is based on several factors that influence it. Some of these factors stimulate the rate of the process while others simply inhibit it. Here we have talked about some of the main factors that influence or limit the process of photosynthesis.


The intensity of light

Light is one of the most important factors in the process of photosynthesis. Its importance can be determined by the fact that with no light present, there will be no photosynthesis occurring. Hence it is highly important that the right amount of light is present with other factors so the process of photosynthesis can happen smoothly. There are two ways in which the intensity of light can have an impact on the rate of photosynthesis, as discussed below:

Low intensity of light:

When the intensity of light is low, it simply drops down the rate of photosynthesis. Even if the carbon dioxide and water are present in more than enough amounts, if there is no light or less light present, the process of photosynthesis will not process successfully.

High intensity of light

On the other hand, if the intensity of light is higher than required, it leads to intensified temperature and transpiration in the plant. When this happens, the stomata of the plant is closed up, and it takes in lesser carbon dioxide. Less carbon dioxide leads to inhibition in the rate of photosynthesis.

Wavelengths of light

Plants absorb the varying wavelengths of light differently. The chlorophyll in the plant is responsible for absorbing the light of two different wavelengths that are red and blue. When the plant is exposed to the light with these wavelengths, the rate of photosynthesis will be increased, and it would be reduced if there were other wavelengths present instead. Hence it is important the right light is present for the plant to exhibit photosynthesis properly.

Presence of carbon dioxide

The amount of carbon dioxide available to the plant majorly influences the rate of photosynthesis. Usually, plants take in the carbon dioxide from the atmosphere, and most of the time, it is not enough for the plant to carry out photosynthesis properly. In this way, it has been observed that when there is a lesser amount of carbon dioxide present for the plant, the rate of photosynthesis is reduced, but there is also an optimum level beyond which the further addition of carbon dioxide will be useless. When the carbon dioxide levels reach maximum for the plant, it starts to absorb the extra carbon dioxide, which results in a decreased rate of photosynthesis.


There are certain reactions of photosynthesis that are influenced by the temperature rates. It has been seen that when the temperature levels rise, the rate of photosynthesis is increased but to a certain extent. Since the enzymes catalyzing the reaction are mainly influenced by the varying temperature rates, the influence only occurs at a specific temperature. That specific point is the optimum temperature, and beyond that, the enzymes do not work. So in order to increase the enzyme activity through temperature, the rate of temperature should not exceed more than the optimum level.

Water intake

The plant’s intake of water during the process of photosynthesis does not have a direct impact on the rate of the process, but it affects it through a series of steps. When there is lesser availability of water for the plant, the plant ends up closing its stomata so that a limited amount of water goes out, avoiding excessive water loss. When this happens, the plants take in less carbon dioxide. Eventually, the rate of photosynthesis is reduced. This is how water intake has an impact on the rate of photosynthesis.


Oxygen is an important factor in the process of photorespiration happening in many plants, mainly the C3 plants. The end product of photorespiration which occurs with the help of oxygen, is carbon dioxide. This released carbon dioxide is essential for the process of photosynthesis. Oxygen is important for the generation of energy that is required during the photosynthesis process. In this way, the presence of oxygen has an impact on the rate of photosynthesis in a plant.

Pigments for photosynthesis

During the process of photosynthesis, the sunlight coming in from the sun is converted into chemical energy, which is utilized by the plant. The sunlight, however, contains light with different wavelengths, and hence the plant absorbs these wavelengths of light in different ways. Some wavelengths are absorbed more than others. Plants have different pigments that absorb different wavelengths of light. A plant pigment is basically a molecule that is known to have a particular color, and based on that color of the pigment; it absorbs lights of different wavelengths. Here we will discuss the most important pigments that are essential for the process of photosynthesis.



Plants have some small structures that are known as the chloroplast. This is the location of the process of photosynthesis in a plant and also where the chlorophyll resides. Since the chlorophyll does not absorb any green light and send it back, this is why plants usually have a green color. Chlorophyll has the capability to absorb light from the two given wavelengths in a light spectrum that is the red and green region. The two main types of chlorophyll, i.e., chlorophyll a and chlorophyll b, are usually involved in the process of absorbing light for photosynthesis, but mainly it is chlorophyll-a that is majorly responsible for converting the light from the sun into the chemical energy that is further used in the process of photosynthesis.


Other than chlorophyll, another pigment is involved in the process of photosynthesis, which is the carotenoids. These pigments usually capture and absorb the violet and blue light from the sun and offer usage in photosynthesis from this energy, but their main role is not concerned with his. In fact, they are actually responsible for the control and management of energy coming to the plant. When light energy is converted to chemical energy, the energy needs to be in a moderate amount that is not too less or too much. The carotenoids make sure that the excess energy coming in is taken care of because it can damage the plant. In this way, carotenoids are essential for the normal functioning of photosynthesis.


Photosynthesis is an important process that occurs in autotrophs like plants. Plants are known to be organisms that make up their own food. They make their food through the process of photosynthesis. This process mainly involves three main components that are water, carbon dioxide and sunlight. When these factors are present in moderate amounts, the plant turns the sunlight into chemical energy, which is used to make food for the plant. When these mentioned factors are present in an unwanted amount, the process of photosynthesis is affected, and hence the plant is unable to make its food in order to function.

Learn all about the process of photosynthesis and other factors associated with it from our private biology tutors.

Find Top Tutors in Your Area

Find A Tutor

With over 3 years of experience in teaching, Chloe is very deeply connected with the topics that talk about the educational and general aspects of a student's life. Her writing has been very helpful for students to gain a better understanding of their academics and personal well-being. I’m also open to any suggestions that you might have! Please reach out to me at chloedaniel402 [at]