Photosynthesis | Reaction, Steps and Importance

What is Photosynthesis in Biology?

Photosynthesis It is the biological phenomena due to which plants make their own food (Glucose) by the usage of sunlight, water, and carbon dioxide. The whole procedure ensues in two major steps. In the initial step, energy is stockpiled in the form of Adenosine Triphosphate (ATP), and Nicotinamide Adenine Dinucleotide Phosphate (NADPH) which comes from light. These two energy currency molecules are used in the subsequent step of this process. In this step organic molecules consequent from carbon dioxide (CO2) by coalescing carbon molecules with each other. it is also recognized as the Calvin Cycle. These organic molecules are utilized by mitochondria to harvest ATP or might be possible they mutually combined to form Glucose, Sucrose, and supplementary Carbohydrates.

Photosynthesis Equation



Photosynthesis Process

Photosynthesis Cycle

The overall summary is given below in the paragraph. Plants take energy from Sunlight and form water the Hydrogen ions and Electrons are obtained which later on syndicates with the carbons which are present in Carbon Dioxide. Despite the fact, a 3-carbon molecule is the unswerving product of this biological phenomena. While Glucose is simply a combination or addition of these two molecules. Glucose being an initial molecule in cellular systems plays a vital role in the proper functioning and development of the whole plant body. 6 gassy molecules of Oxygen molecules are also formed, as a by-product. The plant utilizes this oxygen during oxidative phosphorylation inside Mitochondria. Tinny amount of oxygen is castoff for this purpose while the huge amount is ejected into the Atmosphere which is later on used as for the purpose and allows us to breathe and undergo oxidative phosphorylation, and sugar molecules derived from plants. That is for the reason that 12 water molecules are fragmented during the light reactions, while 6 new molecules are also formed during and afterward the Calvin cycle.

Photosynthesis Diagram



Photosynthesis Formula


Photosynthesis Steps

The whole process takes place in two major steps which are given below:

  1. The Light Reactions
  2. The Dark reaction


Light-Independent Reactions

In the light reaction mainly two systems are functional.  First is PS-I and another one is PS-II.  These photosystems are working together in aggregation with each other by removing electrons and Hydrogens from water. Which are then transference to the ADP and NADP+ cofactors.

During the light reaction with the utilization of light energy, electrons become excited. First of all, they stream by Photosystem II (PSII) and then flow by Photosystem I (PSI). During this process, NADPH is generated. During this phenomena, Protein ATP Synthase also generates ATP synthase.

Where do light reactions occur?

The light reactions materialize in the thylakoid membranes of the Plants Chloroplasts. These thylakoids comprised of compactly crammed clusters of Protein and Enzyme which is known as Photosystems.


The Calvin Cycle

During the Calvin Cycle NADPH and ATP encumbered up with electrons. Calvin Cycle is analogous to the citric acid cycle. The cycle has mainly 3 phases which can be also seen in the chart below:

Calvin Cycle Equation

The Calvin cycle takes place in the Chloroplast stroma.

  1. In the first segment or phase, one Carbon atom is supplementary add to sugar of 5-carbon, generating an unhinged 6-carbon sugar.
  2. In the second segment or phase, 6- Carbon sugar is reduced into 3-carbon sugar two molecules.
  3. In the third phase, the sugar of the five-carbon molecule is redeveloped to flinch the process again.


What is Photosynthesis Waste Product?

The products of the Light  Dependent Reactions and the Calvin Cycle are 3-Phosphoglycerate and G3P.

These two molecules joined and one molecule of glucose is also formed. The whole process is also seen in its chemical equation.

Glucose is the foremost food source for animals and plants. In addition to the sugars molecules, oxygen molecules are also produced as a by-product of this phenomena. Oxygen generated from this reaction energies the living organism for the process o respiration on the planet.

Photosynthesis Worksheet



Here are the few worksheets related to the whole process:

  1. What is the inclusive chemical Reaction for Photosynthesis?

Ans: 6 CO2+ 6 H2O   →   glucose (C6H12O6) + 6 O2


  1. How does Photosynthesis be different from cellular respiration?

Ans: It is the converse process of cellular respiration.


  1. From where does the energy for Photosynthesis come from?

Ans: Sunlight


  1. What plant pigments are intricate in this chemical reaction?

Ans: chlorophyll a, chlorophyll b, and carotenoids.


  1. Explain why chlorophyll appears green to us?

Ans: The green light is reflected by chloroplast (Chlorophyll). Consequently, chlorophyll appearances are green to us.


  1. In what organelle of a plant’s cell photosynthesis occur?

Ans: Chloroplasts


  1. What is photosynthesis surplus products?

Ans: Glucose, Oxygen


  1. What is Calvin Cycle surplus products?

Ans: ATP and NADPH.


  1. In which organelle of a cell does cell respiration occur?

Ans: Mitochondria.


  1. What is wastes product of cellular respiration?

Ans: Carbon dioxide gas, water, and energy.

Photosynthesis Worksheet Answers

Label the diagram below:

Carbon Dioxide             Glucose                Oxygen                Water



  1. In photosynthesis, what constituents come in from the outside?

Ans :______________________________________________________________________________________

6. What ingredients are formed?

Ans :______________________________________________________________________________________

7. The persistence of respiration is to ________________________ the energy

by carbohydrates.

  1. Write the recipe that displays the energy released by the mitochondria?

Ans :______________________________________________________________________________________





    1  A plant pigment that absorbs sunlight. (11)

    4  The links between the energy that carnivores get from eating to the energy captured by photosynthesis. (4,5)

    7  Chlorophyll absorbs every color of sunlight except this. (5)

    8  A compound needed for photosynthesis. (6,7)

   10        The product of photosynthesis. (5)


    2  The process by which plants and some bacteria use the energy from sunlight to produce sugar. (14)

    3  Part of the plant where photosynthesis generally occurs. (6)

    5  A compound needed for photosynthesis. (5)

    6  An animal that eats plants. (9)

    9  A by-product of photosynthesis. (6)

  10 The number of molecules of oxygen produced along with one molecule of sugar. (3)