Photosynthesis definition, steps, equation, process, and diagram

Photosynthesis is the process used by plants, including green ones, and photosynthetic bacteria. electromagnetic radiation is converted to chemical energy. It uses...

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This article writter by Sourav Bio on December 25, 2021

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Photosynthesis definition, steps, equation, process, and diagram
Photosynthesis definition, steps, equation, process, and diagram

Photosynthesis Definition

Photosynthesis is the process used by plants, including green ones, and photosynthetic bacteria. electromagnetic radiation is converted to chemical energy. It uses light energy to transform water and carbon dioxide into oxygen and carbohydrates.

  • The photosynthesis-produced carbohydrate molecules are not just the essential energy to power the energy transfer in ecosystems, but also carbon molecules needed to create biomolecules of a myriad of kinds.
  • Photosynthesis is a light-driven oxidation and reduction reaction in which the energy of the light is utilized to heat water and oxidize it, creating hydrogen ions and oxygen gas and then transfers of electrons into carbon dioxide, which reduces the organic molecules.
  • Autotrophs are the term used to describe photosynthetic organisms because they are able to synthesize chemical fuels like glucose from carbon dioxide as well as water, by using sunlight as a source of energy.
  • Other organisms that get the energy they need from different organisms rely on autotrophs to get energy.
  • One of the primary elements required for photosynthesis is green pigment called chlororophyll. It is found in the chloroplasts in green plants as well as some bacteria.
  • The pigment is crucial to capture sunlight, which will then drive the entire processes of photosynthesis.

Photosynthesis equations/reactions/formula

Oxygenic Photosynthesis

The photosynthesis reaction in general in plants is:

Photosynthesis is a process that differs in both green in comparison to sulfur bacteria. For plants, the water used alongside carbon dioxide for the release of oxygen and glucose molecules. For sulfur bacteria sulfur is used in conjunction alongside carbon dioxide in order to create sulfur, carbohydrates as well as water molecules.

Photosynthesis equations/reactions/formula
Photosynthesis equations/reactions/formula | Source:

6CO2 + 6H2O  +  solar energy   →   C6H12O6 + 6O2

Carbon dioxide + Water  + solar energy → Glucose + Oxygen


Carbon dioxide + Water  + solar energy → Glucose + Oxygen + Water

6CO2 + 12H2O+ solar energy    →    C6H12O6 + 6O2 + 6H2O

Anoxygenic Photosynthesis

The photosynthesis process in general of sulfur bacteria can be described:

CO2 + 2H2S + light energy   →    (CH2O)  + H2O  + 2S

Video: how photosynthesis take place in plants & Process Of Photosynthesis (animated)

Photosynthetic pigments

The pigments of photosynthesis are that absorb electromagnetic radiation, and then transfer all the power of photons absorbed to the center of the reaction which triggers photochemical reactions that occur in living organisms that can photosynthesis. The pigments that are part of the photosynthetic system are extremely widespread and comprised of chlorophylls and carotenoids. Alongside chlorophyll the photosynthetic system also contains another pigment called the pheophytin (bacteriopheophytin found in bacteria) which is a key component when it comes to the exchange of electrons through photosynthesis. Furthermore, different pigments are also present in specific systems of photosynthetic production like xanthophylls found in plants.


The pigment molecules Chlorophyll that acts as the primary photoreceptor that is found in chloroplasts in the majority of green plants. Chlorophylls are composed of the porphyrin ring that is bound by an ion Mg2+ connected to phytol chains. Chlorophylls can be very effective photoreceptors since they have networks that alternate single and double bonds. The electrons in chlorophyll are not confined to any specific nucleus of the atomic and therefore are able to more easily absorb the light energy.

Furthermore, chlorophylls contain absorption bands of solid nature within the visible spectrum in the visible spectrum. Chlorophylls are either found in the cytoplasmic membranes of photosynthetic organisms or thylakoid membranes within plant chloroplasts.


Bacteriorhodopsin is a different kind of photosynthetic pigment that is found only in the halobacteria. It is made up of the protein that is attached to the retinal prosthetic segment. The pigment involved in the absorption of photons. This results in an alteration in the conformation of the protein that results in the elimination of protons from the cell.


Cyanobacteria and red algae use phycobilins like phycoerythrobilin as well as phycocyanobilin, which are light-harvesting pigments. These open-chain tetrapyrroles exhibit the extended polyene system that is found in chlorophylls, however they do not possess their cyclic structure, nor their Central Mg2+. They are covalently connected to specific binding proteins creating phycobiliproteins that join in highly organized complexes called phycobilisomes, which are the main light-harvesting structure in these microorganisms.


Alongside chlorophylls the thylakoid membranes also contain pigments that absorb light or pigments called carotenoids. Carotenoids could be red, yellow or even purple. The most prominent are b-carotene. It is a red-orange isoprenoid and the carotenoid lutein that is yellow. Carotenoid pigments absorb light wavelengths that aren’t absorbed by chlorophylls. They are thus additional light receptors.

Factors affecting photosynthesis

It is the rate at which photosynthesis occurs. can be measured in terms of the production of oxygen or per unit weight (or the area) of plant tissues that are green or per amount of total chlorophyll. The amount of light, carbon dioxide supply, the temperature as well as the supply of water and the mineral content are the main environmental variables that influence photosynthetic rate in terrestrial plants. Its rate at which photosynthesis occurs can also be affected by the plant species along with its physiological state–e.g. its health maturation, whether it is flowering or not.

Photosynthesis Diagram
Photosynthesis Diagram | Source:

1. Light

When intensities of light increase, so does the rate of light-dependent reactions in photosynthesis increases, and consequently speed of photosynthesis also increases. In addition, with increased light intensity and the amount of light falling on leaves rises. In turn, more chlorophyll molecules get being ionized as well as greater amounts of ATPs as well as NADH are produced. After a certain time however, the rate of photosynthesis is constant even as the intensity of the light rises. The rate of photosynthesis is slowed down by other variables. In addition what wavelength light is influences the speed of photosynthesis. Different systems of photosynthesis are able to absorb light energy more efficiently with different wavelengths.

2. Carbon dioxide

A higher concentration of carbon dioxide can increase the rate of carbon being integrated into carbohydrates during the photosynthesis reactions that are light-dependent. So, the increase in the amount of carbon dioxide within the air quickly accelerates the process of photosynthesis to the point at which it is slowed down by other elements.

3. Temperature

Photosynthesis’ light-independent reactions are affected by temperature changes because they are catalyzed enzymes, while light-dependent reactions do not. The rate of reactions rises as enzymes reach their maximum temperature. After that, the rate decreases since the enzymes begin to denature.

4. Minerals

A variety of minerals are necessary to ensure healthy growth of plants and to maximize the rate of photosynthesis. Nitrogen, sulfate iron, magnesium and calcium are needed in large quantities for the production of amino acids proteins, coenzymes deoxyribonucleic acids (DNA) and the ribonucleic acid (RNA), chlorophyll , various other pigments and vital plant components. The smaller amounts of elements such like manganese, copper and chloride are needed in photosynthesis. Other trace elements are essential to fulfill various functions that are not photosynthesis in plants.

5. Water

For plants that live on land water availability could act as a constraint in the photosynthesis process and in plant development. In addition to the need for a tiny amount of water during the photosynthesis process itself large quantities of water escape from the leaves. That is water evaporates out of the leaves and is released into the atmosphere through the stomata. Stomata are tiny holes that are inserted into the epidermis of the leaf, or outer skin. They allow carbon dioxide and let water vapour. 

Stomata can be closed and open in accordance with the physiological requirements that the leaves have. In dry and hot climates, the stomata might close to conserve water however, this can limit the passage of carbon dioxide and consequently increases the speed of photosynthesis. A decrease in transpiration means that there less cooling of leaves and therefore the temperature of the leaf increase. 

The reduced carbon dioxide concentration within the leaves as well as the higher temperatures of the leaves favor the process of photorespiration, which is a wasteful one. If the concentration of carbon dioxide present in atmosphere rises and more carbon dioxide is released, it will get into the stomata through a smaller opening in the stomata. This means that there is a greater chance of photosynthesis with the same amount of water.

6. Internal factors

Every plant species is adaptable to a variety of environmental conditions. Within this variety of conditions, intricate regulatory mechanisms within the plant’s cells regulate the activity of the enzymes (i.e. organic catalysts). These adjustments help maintain equilibrium in the entire photosynthesis process and regulate it in line with the needs of the entire plant. For a particular plant species, for instance increasing the amount of carbon dioxide may result in a temporary increase of two-fold in photosynthetic rate. within a few hours or even days after, however, the rate could fall back to its beginning level as photosynthesis generated more sucrose than the plant could consume. However, a different species that has this carbon dioxide enhancement might be able to make greater amounts of sucrose since it has more carbon-demanding organs and could continue to photosynthesis and increase in size throughout the majority of its lifespan.

Process/ Steps of Photosynthesis

The entire process of photosynthesis is able to be objectively classified into four stages/ processes:

Process/ Steps of Photosynthesis
Process/ Steps of Photosynthesis | Source:

1. Absorption of light

The initial stage of photosynthesis involves the absorption of sunlight by chlorophylls bound to proteins in the thylakoids that make up chloroplasts. The energy absorbed by light is used later to eliminate electrons from electron donors like water, and thereby forming oxygen. The electrons are then transferred to an electron acceptor primary quinine (Q) that is like CoQ within the chain of electron transfers.

2. Electron Transfer

The electrons are transfer from primary electron acceptor by the chain composed of the electron transfer molecules within the thylakoid cellular membrane to that final electron acceptor which is typically NADP+. While electrons are being transferred across the membrane, protons are expelled from the membrane, leading to the gradient of proton through the membrane.

3. Generation of ATP

The movement of protons through the thylakoid lumen into the stroma by the F0F1 complex leads to the production from ATP by combining ADP as well as Pi. This is similar to the process of generating of ATP in the electron transport chain.

4. Carbon Fixation

It is believed that the NADP and ATP produced in steps 2 and 3 supply energy and electrons are the catalyst for reduction of carbon into six-carbon sugar molecules. The first three steps in photosynthesis are dependent upon light energy, and hence are known as light reactions however, the reactions that occur during this step are independent of light, and hence are referred to as dark reactions.

Types/ Stages/ Parts of photosynthesis

Photosynthesis can be split into two stages that are based on the use of light energy

Types/ Stages/ Parts of photosynthesis
Figure: Photosynthesis takes place in two stages: light-dependent reactions and the Calvin cycle. Light-dependent reactions, which take place in the thylakoid membrane, use light energy to make ATP and NADPH. The Calvin cycle, which takes place in the stroma, uses energy derived from these compounds to make GA3P from CO2. Image Source: OpenStax (Rice University).

1. Light-dependent reactions

The photosynthesis-related reactions that depend on light occur only when bacteria or plants are illuminated. In the light-dependent reaction, chlorophyll as well as other pigments in photosynthesis cells absorb energy from light and store it in ATP and NADPH as they simultaneously transform into O2 gas. In light-dependent reactions in photosynthesis, chlorophyll is able to absorb intense, short-wavelength, light, which stimulates electrons in the thylakoid cell membrane.

Electrons are excited and begins the process of changing the energy of light in chemical energy. The light reactions are carried out in two photosystems which are found in the thylakoid that is found in chloroplasts.

Light-dependent reactions of photosynthesis at the thylakoid membrane
Figure: Light-dependent reactions of photosynthesis in the thylakoid membrane of plant cells. Image Source: Wikipedia (Somepics).

Photosystem II

The Photosystem II is a collection of pigments and proteins that collaborate for absorption of light and move electrons through a series of molecules till it is able to reach an acceptor of electrons. Photosystem II has a pair of chlorophyll molecule, also called P680 as they are the ones that absorb light with the wavelength of 680 nm.

The P680 provides a pair electrons after it absorbs light energy, leading to an oxidized version of P680. In the end, an enzyme is responsible for the division of a water-based molecule into the two electrons of an electron, two hydrogen ions as well as oxygen molecules. The electrons transfer to P680, which causes it to go back to its initial state.

Photosystem I

Photosystem I is a corresponding complex to photosystem II, except that in my photosystem, I have two chlorophyll molecules, known as P700 since they are the best absorbers of wavelength of 700 num. Because photosystem I absorbs sunlight, it is excited and transmits electrons. The oxidized version of P700 is then able to accept one electron of photosystem II and return to its initial stage.

The electrons released by photosystem I are passed through a series of reactions with redox through ferredoxin, a protein. The electrons eventually arrive at NADP+, and are reduced to NADPH.


2 H2O + 2 NADP+ + 3 ADP + 3 Pi + light → 2 NADPH + 2 H+ + 3 ATP + O2

2. Light independent reactions (Calvin cycle)

Photosynthesis-related light independent reactions are anabolic reactions that result in the creation of a sex-carbon compound, glucose , in plants. The reactions that occur in this stage are often referred to as dark reactions because they do not directly depend on light energy however, they do require the product produced by light-induced reactions.

LightLight-independent reactions-independent reactions
Figure: Overview of the Calvin cycle pathway. Image Source: Wikipedia (Mike Jones).

This phase is comprised of 3 additional steps that result in carbon fixation/assimilation.

Step 1: Fixation of CO2 into 3-phosphoglycerate

In this stage, one CO2 molecule is connected to the compound of five carbons ribulose 1,5-biphosphate , which is catalyzed by enzyme ribulose 1,5-biphosphate carboxylase which is also known as rubisco. The bonding process results in creation of an unsteady six-carbon compound which is then broken down to form three molecules, which are 3-phosphoglycerate.

Step 2: Conversion of 3-phosphoglycerate to glyceraldehydes 3-phosphate

The 3-phosphoglycerate that is formed in the first step is converted into glyceraldehyde-3-phosphate through two distinct reactions. At first, enzyme 3-phosphoglycerate kinase present in the stroma catalyzes the transfer of a phosphoryl group from ATP to 3-phosphoglycerate, yielding 1,3-bisphosphoglycerate. Then, NADPH donates electrons in an enzymatic reaction triggered by chloroplast-specific isozyme glyceraldehyde 3 dehydrogenase. This results in the production of glyceralde as well as phosphoglycerate (Pi).

The majority of the 3-phosphate glyceraldehyde that is produced is used to make the ribulose 1,5-bisphosphate. The remaining Glyceraldehyde can be converted into starch inside the chloroplast, and stored for use later or exported to the cytosol where it is converted into sucrose to transport to the growing regions of the plant.

Step 3: Regeneration of ribulose 1,5-biphosphate from triose phosphates

The three-carbon compounds that are formed during the earlier steps are transformed into the compound with five carbons called ribulose 1,5-biphosphate, through several transformations using intermediates made of three, four, -, fivesix and 7-carbon sugar. The first molecules of the process, when they are regenerated during photosynthesis, the process produces the formation of a cicle (Calvin cycle).


3 CO2 + 9 ATP + 6 NADPH + 6 H+    →     glyceraldehyde-3-phosphate (G3P) + 9 ADP + 8 Pi + 6 NADP+ + 3 H2O

A G3P molecule has three carbon atoms that are fixed It takes therefore two G3Ps to make a six-carbon glucose molecule. It will take six rounds of the cycle in order to make one glucose molecule.

Video: Photosynthesis: Light Reaction, Calvin Cycle, and Electron Transport (Animation)

Regulation of the cycle

Photosynthesis is not possible in the night, however, glycolysis, a process that utilizes the same reactions as those in the Calvin-Benson cycles, with the exception of the reverse, takes place. This means that certain steps in the cycle would be inefficient when they are allowed to take place in darkness, as they could impede the process of glycolysis. In this regard, certain enzymes in the Calvin-Benson cycle can be “turned off” (i.e. they become inactive) in darkness.

In the absence of sunlight, changes in physiological conditions often require adjustments to the rate of reaction in the Calvin-Benson cycle such that enzymes that are involved in some reactions alter their catalytic activities. These changes in enzyme activity are typically caused through changes in the levels of chloroplast components such as reduced ferredoxin and acids and the soluble components (e.g., Pi and magnesium ions).

Energy efficiency of photosynthesis

The efficiency of photosynthesis in energy can be measured by the ratio between power stored to energy that is absorbed. The energy stored in the chemical is the difference in the energy found in gaseous oxygen and organic compounds and the energy contained in carbon dioxide, water, and the rest of the reactants. How much energy is stored cannot be calculated because a variety of products are created, and these depend on the species of plant and the environmental conditions. When the formula for glucose production mentioned earlier is used to estimate the actual process of storage, that 1 mole (i.e., 6.02 x 1023 molecules abbreviated”N”) of oxygen as well as one sixth mole of glucose leads to the storage of approximately 117 Kilocalories (kcal) in chemical energy. The amount is then evaluated against the energy absorbed by light to create one mole of oxygen to determine the effectiveness of photosynthesis.

Light is an atomized wave known as photons. They are energy units, also known as light quanta. The number N photons is known as an Einstein. The energy of light changes in inverse proportion to the length of the photon’s waves which means that less wavelength the higher it is the amount of energy. Energy (e) of the photon is determined in the formula e = hc/l in which c is the speed of light and h is Planck’s constant, and the l is the wavelength of light. Its energy (E) from an instein has the formula E = Nhc/l = 28,600/l when E is expressed in Kilocalories and l is expressed in nanometres (nm 1 nm = 10-9 meters). Einsteins of red light that has the wavelength of 680 nanometers has a energy of around 42 kcal. Light that is blue has lower wavelength, and thus has more energetic than light from red. No matter whether the light is red or blue it is the same number of Einsteins are needed for photosynthesis, per mole of oxygen produced. The portion of the solar spectrum that plants use has an estimated wavelength of 570 nm. consequently, the energy of the light that is used in photosynthesis is about 28,600/570 which is 50 kcal for each einstein.

To determine what amount of energy is that is involved in photosynthesis, another measurement is required to be determined: the number of Einsteins absorption per mole of oxygen that has evolved. This is referred to as Quantum requirement. The quantum requirement minimum for photosynthesis in optimal conditions is approximately nine. Therefore, the energy required is 9 x 50 which is 450 kcal for each mole of oxygen that has evolved. Thus, the maximum estimated efficiency of photosynthesis in energy is the energy that is stored for each mole developed which is 117 kcal. This energy is divided by 450, that is 117/450 or 26 percent.

The actual proportion that plants store solar energy is lower than the maximum effectiveness of the process. A crop that produces agricultural yields where the biomass (total dry weight) can store up to 1 percent of the total solar energy across the entire year is rare, though some instances of greater yields (perhaps even 3.5 percent of sugarcane) have been mentioned. There are a variety of reasons behind the difference between the expected maximal efficiency in photosynthesis and actual energy stored by biomass. For one, more than half the sunlight that hits is made up of wavelengths too long be absorbed. A portion of it is lost or reflected back onto the leaf. Thus, plants are able to absorb at most 34 percent of incident sunlight. In addition, they perform a range of physiological processes within nonphotosynthetic tissue as stems and roots. These processes, along with the cellular respiration process in all plant parts consume stored energy. Thirdly, the rate of photosynthesis in bright light often exceed the requirements of the plant and result in the production of excessive glucose and starch. If this occurs the regulatory mechanisms of the plant reduce the rate of photosynthesis, which allows the sunlight that is absorbed to remain unutilized. Fourth In many plants, energy is wasted through this process called photorespiration. In addition, the growing season could be only for a few months of the year. The sunlight absorbed during other seasons isn’t utilized. Additionally, it must be noted that if just agriculture-related products (e.g. fruits, seeds and tubers, rather than the total biomass) are considered to be the product that comes out of the process of energy conversion photosynthesis, efficiency declines further.

Light-dependent reactions vs. light-independent reactions

There are numerous stages involved in photosynthesis, it is broken down into two primary phases: light-dependent reactions and light-independent reactions. The light-dependent reaction occurs in the thylakoid membrane. It requires a constant stream of sunlight. This is the reason for the name light-dependent reactions. The chlorophyll is able to absorb energy from sunlight, and this energy transforms into chemical energy, in the form of chemical molecules ATP or NADPH. The stage that is light-dependent which is also called also known as Calvin Cycle, takes place within the stroma. It is the region between the thylakoid membranes as well as the chloroplast membranes. It doesn’t require light. This is why it’s called a the light-dependent reaction. At this point, energy generated from ATP as well as NADPH compounds is utilized to create carbohydrate molecules, including glucose, derived from carbon dioxide.

Products of Photosynthesis

The results of photosynthesis’ light-dependent reactions include:

  • ATP
  • O2
  • H+ ions

The products of light-dependent reaction (Calvin cycle) of photosynthesis include:

  • glyceraldehyde-3-phosphate (G3P) / Glucose (carbohydrates)
  • H+ ions

The primary photosynthesis products are:

  • Glucose (carbohydrates)
  • Water
  • Oxygen
  • Sulfur (in photosynthetic sulfur bacteria)

Photosynthesis examples

Photosynthesis in green plants or oxygenic bacteria

In the plants and oxygenic bacteria such as cyanobacteria and cyanobacteria photosynthesis occurs with the help of the green pigment called chlorophyll. It occurs in the thylakoids within the chloroplasts and results in the products such as oxygen gas, glucose and water molecules. Most sugar units in plants are connected to form fructose or starch, and even sucrose.

Photosynthesis in sulfur bacteria

In purple sulfur bacteria photosynthesis happens when there is hydrogen sulfur, not water. Some of these bacteria such as green sulfur bacteria contain chlorophyll, whereas other purple sulfur bacteria possess carotenoids, which are pigments used in photosynthetic processes. The products of photosynthesis these bacteria is sugars (not always glucose) as well as sulfur gas as well as water molecules.

Importance of photosynthesis

  • Photosynthesis is the principal source of energy for autotrophs. They make their food with sunlight, carbon dioxide and pigments from photosynthetic.
  • Photosynthesis is equally important for heterotrophs, since they get their energy from autotrophs.
  • The process of photosynthesis in plants is essential to ensure the levels of oxygen in the air.
  • Additionally, the byproducts from photosynthesis also contribute to the carbon cycle that occurs within the oceans on land as well as animals and plants.
  • In the same way, it aids in maintaining a symbiotic connection between animals, plants, and human beings.
  • The sun’s energy, also known as solar energy, is the most important source for all forms of energy that exist on earth that is utilized in the process of photosynthesis.
Importance of photosynthesis
Importance of photosynthesis

Artificial photosynthesis

Artificial photosynthesis is an organic process that is modeled after the natural process of utilization for water, sunlight, and carbon dioxide to make carbohydrates and oxygen.

Artificial photosynthesis
Artificial photosynthesis Artificial photosynthesis | Image Source: Phys.
  • In the process of artificial photosynthesis, photocatalysts are used equipped to replicate the reduction-oxidation reactions that occur during natural photosynthesis.
  • The primary purpose of artificial photosynthesis is to generate solar energy by absorbing sunlight. It can then be stored and used in circumstances when sunlight isn’t available.
  • When solar fuels are made artificial photosynthesis is used to make oxygen from sunlight and water which results in the production of clean energy.
  • The most significant aspect of artificial photosynthesis photocatalytic breaking of a water molecule, which results in oxygen and huge quantities of hydrogen gas.
  • Additionally, light-driven reduction of carbon can be used to mimic the natural process of carbon fixation, which results in the formation of carbohydrates molecules.
  • Thus, artificial photosynthesis has applications in the production of solar fuels, photoelectrochemistry, engineering of enzymes, and photoautotrophic microorganisms for the production of microbial biofuel and biohydrogen from sunlight.

The molecular biology of photosynthesis

Oxygenic photosynthesis is a feature of prokaryotic cells known as cyanobacteria, and in the eukaryotic plant cells (algae as well as higher plant). In the eukaryotic plant cells that contain chloroplasts as well as nucleus, the genetic information necessary to reproduce the apparatus for photosynthesis is located in a portion of the chloroplast’s chromosome, and in part in the nucleus chromosomes. For instance the carboxylation enzyme, carboxylase ribulose 1,5-bisphosphate is a large protein molecule that consists of an array of eight polypeptide subunits that are large as well as eight small subunits of polypeptides.

The gene for the larger subunits is found in the chromosome of the chloroplast, while the gene that controls the smaller subunits is found in the nucleus. The transcription of the DNA of the nuclear gene produces messenger RNA (mRNA) that contains the information needed to synthesize tiny polypeptides. When this synthesis is carried out by cytosolic and ribosomes, additional amino acid residues will be introduced to form an identification leader at one end of the chain.

The leader is identified by specific receptor sites in the outer chloroplast membrane. These receptors permit the polypeptide to be able to penetrate the membrane and into the chloroplast. The leader is eliminated and the smaller subunits are combined with the larger subunits that have been synthesized by chloroplast-derived ribosomes, according to mRNA transcription from chloroplast DNA. Nuclear genes are expressed. which code for proteins required in the chloroplasts is controlled by the events occurring in the chloroplasts , in some instances, for instance, the production of nuclear encoded chloroplast enzymes can only occur after the absorption of light by chloroplasts.


Q1. where does photosynthesis take place?

In plants, photosynthesis takes place in chloroplasts, which contain the chlorophyll. Chloroplasts are surrounded by a double membrane and contain a third inner membrane, called the thylakoid membrane, that forms long folds within the organelle.

Q2. what are the reactants of photosynthesis?

The process of photosynthesis is commonly written as: 6CO2 + 6H2O → C6H12O6 + 6O2. This means that the reactants, six carbon dioxide molecules and six water molecules, are converted by light energy captured by chlorophyll (implied by the arrow) into a sugar molecule and six oxygen molecules, the products.

Q3. how are photosynthesis and cellular respiration related?

Photosynthesis is the process by which atmospheric carbon dioxide is assimilated and converted to glucose and oxygen is released. CO2 and H2O are utilised in the process. In the cellular respiration, glucose is broken down to CO2 and energy is released in the form of ATP, which is utilised in performing various metabolic processes. Oxygen is utilised in the process. Energy is stored in the process of photosynthesis, whereas it is released in the process of cellular respiration.

The process of cellular respiration and photosynthesis complement each other. These processes help cells to release and store the energy respectively. They are required to keep the atmospheric balance of carbon dioxide and oxygen concentrations.

Q4. what is the equation for photosynthesis?

The process of photosynthesis is commonly written as: 6CO2 + 6H2O → C6H12O6 + 6O2

Q5. where does photosynthesis occur?


Q6. what are the products of photosynthesis?

Let’s look at the products of photosynthesis! During the process of photosynthesis plants break apart the reactants of carbon dioxide and water and recombine them to produce oxygen (O2) and a form of sugar called glucose (C6H12O6).

Q7. why is photosynthesis important?

Photosynthesis is the main source of food on earth. It releases oxygen which is an important element for the survival of life. Without photosynthesis, there will be no oxygen on earth. The stored chemical energy in plants flows into herbivores, carnivores, predators, parasites, decomposers, and all life forms.

Q8. which of these equations best summarizes photosynthesis?

A. C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy

B. C6H12O6 + 6 O2 → 6 CO2 + 12 H2O

C. 6 CO2 + 6 H2O → C6H12O6 + 6 O2

D. 6 CO2 + 6 O2 → C6H12O6 + 6 H2O

E. H2O → 2 H+ + 1/2 O2 + 2e-

Ans: C. 6 CO2 + 6 H2O → C6H12O6 + 6 O2

Q9. what are the raw materials of photosynthesis?

The raw materials of photosynthesis, water and carbon dioxide, enter the cells of the leaf. Oxygen, a by-product of photosynthesis, and water vapor exit the leaf.

Q10. which gas is removed from the atmosphere during photosynthesis?

Photosynthesis removes CO2 from the atmosphere and replaces it with O2.

Q11. which of the following sequences correctly represents the flow of electrons during photosynthesis?

  • A. NADPH → O2 → CO2
  • B. H2O → NADPH → Calvin cycle
  • C. NADPH → chlorophyll → Calvin cycle
  • D. H2O → photosystem I → photosystem II


The correct option is B

H2O → NADPH → Calvin cycle

Electrons flow from water through the photosystem II, electron transport chain, and photosystem I to NADP+. The electrons of NADPH thus formed are then used in the Calvin cycle.

Q12. what organelle does photosynthesis occur in


Q13. what are the inputs of photosynthesis?

In photosynthesis, water, carbon dioxide, and energy in the form of sunlight are inputs, and the outputs are glucose and oxygen.

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