The Stages of photosynthesis Can be divided according to the amount of sunlight that the plant receives. Photosynthesis is the process by which plants and algae feed. This process consists of the transformation of light into energy, necessary for survival.
Unlike humans that need external agents such as animals or plants to survive, plants can create their own food through photosynthesis.
The word photosynthesis is composed of two words: photo and synthesis. Photo means light and synthesis blend. Therefore, this process Literally consists in turning light into food.
The organisms Which are capable of synthesizing substances to create food, as well as plants, algae and some bacteria, are referred to as autotrophs.
Photosynthesis requires light, carbon dioxide and water to be made. Carbon dioxide from the air enters the leaves of the plant thanks to the pores found in them. On the other hand, water is absorbed by the roots and moves to the leaves and the light is absorbed by the pigments of the leaves.
During these phases, the elements of photosynthesis, water and carbon dioxide, enter the plant and the products of photosynthesis, oxygen and sugar, leave the vegetable.
Phases / Stages of photosynthesis
First, the energy of light is absorbed by proteins found in chlorophyll. Chlorophyll is a pigment that is present in the tissues of green plants; Usually photosynthesis occurs in the leaves, specifically in tissue called mesophyll.
Each cell of mesophyll tissue contains organisms called Chloroplasts . These organisms are designed to carry out photosynthesis. In each chloroplast are clustered structures called tilacoides, which contain chlorophyll.
This pigment absorbs light, therefore it is mainly responsible for the first interaction between the plant and light
In the leaves there are small pores called stomas. They are responsible for letting carbon dioxide spread into the mesophyll tissue and for oxygen to escape into the atmosphere. Thus, l To photosynthesis occurs in two stages: the luminous phase and the dark phase.
Luminous phase
These reactions only occur when light is present and occurs in the thylakoid membrane of chloroplasts. In this phase, the energy that comes from sunlight is transformed into chemical energy. This energy will be used as gasoline to be able to assemble the glucose molecules.
The transformation to chemical energy happens through two chemical compounds: ATP, or molecule that saves energy, and NADPH, which carries reduced electrons. It is during this process that the water molecules become the oxygen we find in the environment.
Solar energy is converted into chemical energy in a complex of proteins called photosystem. There are two photosystems, both found within the chloroplast. Each photosystem has multiple proteins that contain a mixture of molecules and pigments such as chlorophyll and carotenoids to allow the absorption of sunlight.
In turn, the pigments of photosystems act as a vehicle to channel energy, as they move it to the reaction centers. When light attracts a pigment, it transfers energy to a nearby pigment. This near pigment can also transmit that energy to some other nearby pigment and so the process is repeated successively.
These luminous phases begin in photosystem II. Here, the light energy is used to divide the water.
This process releases electrons, hydrogen and oxygen. The electrons charged with energy are transported to photosystem I, where ATP is released. In oxygenic photosynthesis the first donor electron is water and the oxygen created will be waste. In anoxygenic photosynthesis, several donor electrons are used.
In the light phase is captured light energy that is stored temporarily in the chemical molecules of ATP and NADPH. The ATP will be decomposed to release energy and the NADPH will donate its electrons to convert carbon dioxide molecules into sugars.
Dark phase
In the dark phase, carbon dioxide from the atmosphere is captured to be modified when hydrogen is added to the reaction.
Thus, this mixture will form carbohydrates that will be used by the plant as food. It is called dark phase because the light is not directly necessary for it to take place. But even though light is not necessary for these reactions to take place, this process requires the ATP and NADPH to be created in the light phase.
This phase occurs in the stroma of chloroplasts. Carbon dioxide enters the interior of the leaves through the chloroplast stroma. Carbon atoms are used to build sugars. This process is carried out thanks to the ATP and NADPH formed in the previous reaction.
Dark Phase Reactions
First, a carbon dioxide molecule is combined with a carbon receptor molecule called RuBP, resulting in an unstable 6-carbon compound.
Immediately this compound is divided into two carbon molecules that receive energy from ATP and produce two molecules called BPGA.
Then, an electron of NADPH is combined with each of the molecules BPGA to form two molecules of G3P.
These G3P molecules will be used to create glucose. Some G3P molecules will also be used to replenish and restore RuBP, necessary for the cycle to continue.
Importance of photosynthesis
Photosynthesis is important because it produces food for plants and oxygen. Without photosynthesis, it would not be possible to consume many fruits and vegetables necessary for the human diet. Also, many animals that consume humans could not survive without feeding on plants.
On the other hand, the oxygen that plants produce is necessary so that all life on Earth, including humans, can survive. Photosynthesis is also responsible for maintaining stable levels of oxygen and carbon dioxide in the atmosphere. Without photosynthesis, life on Earth would not be possible.
References
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