All living organisms that we can observe in our plant, including human beings, need energy to be able to cause the different metabolic reactions that participate in growth , development and reproduction . However, organisms cannot use energy from light directly to meet all of their metabolic needs , since energy must first be transformed into chemical energy and this requires the process known as photosynthesis .

What is photosynthesis?

It is the energy- driven process by which light energy is transformed into chemical energy in the form of sugars, forming glucose and sugar molecules from water , carbon dioxide while releasing oxygen as a by-product.

  • What does it consist of
  • Photosynthesis characteristics
  • Source
  • History
  • What is it for
  • Elements of photosynthesis
  • What organisms carry out photosynthesis
  • Where photosynthesis takes place
  • Types
  • Process or stages
  • Formula
  • End products of photosynthesis
  • Importance

What does it consist of

Photosynthesis is a chemical process used by plants through which chemical energy is produced from solar light energy . Using this energy, plants convert water in the soil and carbon dioxide in the air into glucose , an important nutrient that provides energy and produces cellulose. Photosynthesis is the most important chemical process by means of which organic substances are synthesized from solar light energy.

Photosynthesis characteristics

The main characteristics of photosynthesis are the following:

  • Almost all the energy consumed by living things in the biosphere comes from photosynthesis .
  • The structural unit of photosynthesis is the chloroplast .
  • They have flattened sacs or vesicles called thylakoids , which contain photosynthetic pigments.
  • Chemical energy is produced from solar light energy.
  • It is the most important chemical process on Earth, because through it organic substances are synthesized from solar light energy .
  • The energy source for photosynthesis is sunlight and its main source of hydrogen is water .
  • It is considered as the basic form of nutrition of the kingdom Plantae .
  • It has a light phase and a dark phase .


The origin of photosynthesis is believed to be in eukaryotes . Several molecular studies point to the origin of green plants in the Precambrian era , although scientists claim to have found fossils long before that could be attributed to ancestors of chlorobionts .


In Ancient Greece , it was Aristotle who proposed a hypothesis that sunlight was related to the green color of plants. It was analyzed again in the seventeenth century, when Stephen Hales made mention of the hypothesis stating that the air that penetrated through the leaves in the vegetables was used as a source of food.

In 1778 , the physician Jan Ingenhousz made experiments on the production of oxygen by plants. He discovered that plants, when illuminated with sunlight , released air with oxygen . He also concluded that photosynthesis took place in the green parts of the plant.

Jean Senebier , established the need for light for the assimilation of carbon dioxide and the release of oxygen and established that even under lighting conditions , if CO2 is not supplied , no release of oxygen is recorded. In 1905, Frederick Frost Blackman was able to measure the rate at which photosynthesis occurs under different conditions. In 1920, Cornelius Bernardus van Niel proposed that the oxygen released in photosynthesis came from water and not from carbon dioxide . In 1937, Robert Hill showed thatchloroplasts are capable of producing oxygen in the absence of carbon dioxide

An important character in the study was plant physiologist Daniel Arnon who used components from spinach leaves to carry out photosynthesis in the total absence of cells to explain how they assimilate carbon dioxide and how they form ATP.

What is it for

The photosynthesis process helps plants to be able to feed , grow and develop , and thanks to them, green plants are able to transform water and carbon dioxide into oxygen and energy- rich substances . It also serves to obtain oxygen in the atmosphere , necessary for the proper development of living beings. It is a fundamental part of man’s life, because through it plants can grow and become one of the sources of food most important thing that man has.

Elements of photosynthesis

The following are the elements necessary for photosynthesis:

  • Light : it is necessary because plants carry out photosynthesis depending on the amount of light they receive.
  • The temperature : it must range between 10º and 35º C. Otherwise, the enzymes could be damaged.
  • Photosynthetic pigments : the main one is chlorophyll, which is the molecule that allows the capture of energy from the sun during the photosynthesis process.
  • Carbon dioxide : Photosynthesis can be strengthened when the amount of CO2 is increased , until it reaches a level that stabilizes the performance of the process.
  • Water : when there is little water then the stomata close and do not allow adequate gas exchange between the leaves and the atmosphere.
  • Minerals : when there is a very little amount of Calcium , Nitrogen and Magnesium , there is an affectation in the development of the plants.

What organisms carry out photosynthesis

Organisms that are capable of photosynthesis are known as photo autotrophs and are made up of green plants , algae, and some bacteria . The process is performed by algae green blue , green bacteria , and purple bacteria and eukaryotic organisms both unicellular as euglenoideas , dinoflagellates and diatoms as the multicellular algae that may be green, red and brown and the green plants above . There are also some organismsprotists that are capable of producing photosynthesis because they have a structure similar to that of plants such as the algae Euglena and Volvox. Also, some types of bacteria such as cyanobacteria .

Where photosynthesis takes place

Photosynthesis takes place mainly in the chloroplasts that contain the leaves of plants . The leaves have an epidermis known as the mesophyll or middle layer, which have vascular bundles that are the channels through which the nutritive substances and water travel and the stomata, which are the holes that make gas exchange possible .


There are basically two types of photosynthesis: bacterial anoxygenic photosynthesis or in which oxygen is not produced and oxygenic or plant photosynthesis , in which oxygen is released and which is the most common.

Plant photosynthesis

Plants take up carbon dioxide found in the air and water from the soil and, using energy from the sun , synthesize glucose , which is rich in energy and releases oxygen . It is a process that occurs in the leaves thanks to chlorophyll, a pigment contained in chloroplasts .

Bacterial photosynthesis

In bacterial photosynthesis Anoxygenic or organisms do not use the water as a supplier element electrons , so it is not produced oxygen.  Three bodies providing this type of photosynthesis: the purple sulfur bacteria and sulfur bacteria green and green bacteria using organic material as the electron – donating substance.

Process or stages

There are two different phases in the photosynthesis process, these are the following:

  • Light phase : there is the participation of sunlight . It occurs in thylakoids of the chloroplast , which are immersed in a solution called sacks stroma . Chlorophyll captures sunlight and this breaks down the water molecule, producing the separation of hydrogen from oxygen . Oxygen is released into the atmosphere and energy that is not used is stored in ATP molecules.
  • Dark phase : does not need solar energy . It is produced in the stroma of the chloroplast and in it, the hydrogen that arose from the light phase joins the carbon dioxide producing organic compounds , mainly carbohydrates.


The photosynthesis process needs different types of chemical reactions so that it can be carried out correctly, and it can be expressed using the following chemical formula :

Carbon Dioxide + Water (+ Sunlight) → Glucose + Oxygen

6 CO2 + 6 H2O → C6H12O6 + 6 O2

The process takes place thanks to the presence of sunlight, which allows the plant to transform carbon dioxide and water into nutrients and oxygen that is then released as waste . At the same time, the chemical elements of the formula enter and leave the cells of the plant by diffusion or osmosis , which allows the plant to take carbon dioxide from the air and subsequently release oxygen to it.

End products of photosynthesis

The three main products that result from the photosynthesis process are:

  • Glucose : is the simple sugar that is used in different ways depending on the requirements of the plant. It can be immediately consumed by plant cells, it can be stored in the form of insoluble starch , it can be converted into sucrose or used in the synthesis of fats and proteins .
  • Water: it is produced during the process and can be reused by the plant in the process.
  • Oxygen : a small part is used in the respiration of cells, but most of the oxygen is released into the atmosphere through the stomata .


Photosynthesis is a process that provides us with most of the oxygen that is necessary to survive and breathe . It is a crucial process of transforming energy to be able to produce oxygen , which is why it helps to maintain a balanced level of oxygen and carbon dioxide in the atmosphere. It participates in the composition of the Earth’s atmosphere as it produces oxygen gas as a by-product. It removes significant amounts of carbon dioxide from the atmosphere and uses carbon atoms to create organic molecules .

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