what is the meaning of synthesis in photosynthesis

ENCYCLOPEDIC ENTRY

Photosynthesis.

Photosynthesis is the process by which plants use sunlight, water, and carbon dioxide to create oxygen and energy in the form of sugar.

Loading ...

Learning materials, instructional links.

• Photosynthesis (Google doc)

Most life on Earth depends on photosynthesis .The process is carried out by plants, algae, and some types of bacteria, which capture energy from sunlight to produce oxygen (O 2 ) and chemical energy stored in glucose (a sugar). Herbivores then obtain this energy by eating plants, and carnivores obtain it by eating herbivores.

The process

During photosynthesis, plants take in carbon dioxide (CO 2 ) and water (H 2 O) from the air and soil. Within the plant cell, the water is oxidized, meaning it loses electrons, while the carbon dioxide is reduced, meaning it gains electrons. This transforms the water into oxygen and the carbon dioxide into glucose. The plant then releases the oxygen back into the air, and stores energy within the glucose molecules.

Chlorophyll

Inside the plant cell are small organelles called chloroplasts , which store the energy of sunlight. Within the thylakoid membranes of the chloroplast is a light-absorbing pigment called chlorophyll , which is responsible for giving the plant its green color. During photosynthesis , chlorophyll absorbs energy from blue- and red-light waves, and reflects green-light waves, making the plant appear green.

Light-dependent Reactions vs. Light-independent Reactions

While there are many steps behind the process of photosynthesis, it can be broken down into two major stages: light-dependent reactions and light-independent reactions. The light-dependent reaction takes place within the thylakoid membrane and requires a steady stream of sunlight, hence the name light- dependent reaction. The chlorophyll absorbs energy from the light waves, which is converted into chemical energy in the form of the molecules ATP and NADPH . The light-independent stage, also known as the Calvin cycle , takes place in the stroma , the space between the thylakoid membranes and the chloroplast membranes, and does not require light, hence the name light- independent reaction. During this stage, energy from the ATP and NADPH molecules is used to assemble carbohydrate molecules, like glucose, from carbon dioxide.

C3 and C4 Photosynthesis

Not all forms of photosynthesis are created equal, however. There are different types of photosynthesis, including C3 photosynthesis and C4 photosynthesis. C3 photosynthesis is used by the majority of plants. It involves producing a three-carbon compound called 3-phosphoglyceric acid during the Calvin Cycle, which goes on to become glucose. C4 photosynthesis, on the other hand, produces a four-carbon intermediate compound, which splits into carbon dioxide and a three-carbon compound during the Calvin Cycle. A benefit of C4 photosynthesis is that by producing higher levels of carbon, it allows plants to thrive in environments without much light or water. The National Geographic Society is making this content available under a Creative Commons CC-BY-NC-SA license . The License excludes the National Geographic Logo (meaning the words National Geographic + the Yellow Border Logo) and any images that are included as part of each content piece. For clarity the Logo and images may not be removed, altered, or changed in any way.

Media Credits

The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. The Rights Holder for media is the person or group credited.

Production Managers

Program specialists, last updated.

March 20, 2024

User Permissions

For information on user permissions, please read our Terms of Service. If you have questions about how to cite anything on our website in your project or classroom presentation, please contact your teacher. They will best know the preferred format. When you reach out to them, you will need the page title, URL, and the date you accessed the resource.

If a media asset is downloadable, a download button appears in the corner of the media viewer. If no button appears, you cannot download or save the media.

Text on this page is printable and can be used according to our Terms of Service .

Interactives

Any interactives on this page can only be played while you are visiting our website. You cannot download interactives.

Related Resources

This page has been archived and is no longer updated

Photosynthetic Cells

Cells get nutrients from their environment, but where do those nutrients come from? Virtually all organic material on Earth has been produced by cells that convert energy from the Sun into energy-containing macromolecules. This process, called photosynthesis, is essential to the global carbon cycle and organisms that conduct photosynthesis represent the lowest level in most food chains (Figure 1).

What Is Photosynthesis? Why Is it Important?

Most living things depend on photosynthetic cells to manufacture the complex organic molecules they require as a source of energy. Photosynthetic cells are quite diverse and include cells found in green plants, phytoplankton, and cyanobacteria. During the process of photosynthesis, cells use carbon dioxide and energy from the Sun to make sugar molecules and oxygen. These sugar molecules are the basis for more complex molecules made by the photosynthetic cell, such as glucose. Then, via respiration processes, cells use oxygen and glucose to synthesize energy-rich carrier molecules, such as ATP, and carbon dioxide is produced as a waste product. Therefore, the synthesis of glucose and its breakdown by cells are opposing processes.

However, photosynthesis doesn't just drive the carbon cycle — it also creates the oxygen necessary for respiring organisms. Interestingly, although green plants contribute much of the oxygen in the air we breathe, phytoplankton and cyanobacteria in the world's oceans are thought to produce between one-third and one-half of atmospheric oxygen on Earth.

What Cells and Organelles Are Involved in Photosynthesis?

Chlorophyll A is the major pigment used in photosynthesis, but there are several types of chlorophyll and numerous other pigments that respond to light, including red, brown, and blue pigments. These other pigments may help channel light energy to chlorophyll A or protect the cell from photo-damage. For example, the photosynthetic protists called dinoflagellates, which are responsible for the "red tides" that often prompt warnings against eating shellfish, contain a variety of light-sensitive pigments, including both chlorophyll and the red pigments responsible for their dramatic coloration.

What Are the Steps of Photosynthesis?

Photosynthesis consists of both light-dependent reactions and light-independent reactions . In plants, the so-called "light" reactions occur within the chloroplast thylakoids, where the aforementioned chlorophyll pigments reside. When light energy reaches the pigment molecules, it energizes the electrons within them, and these electrons are shunted to an electron transport chain in the thylakoid membrane. Every step in the electron transport chain then brings each electron to a lower energy state and harnesses its energy by producing ATP and NADPH. Meanwhile, each chlorophyll molecule replaces its lost electron with an electron from water; this process essentially splits water molecules to produce oxygen (Figure 5).

Once the light reactions have occurred, the light-independent or "dark" reactions take place in the chloroplast stroma. During this process, also known as carbon fixation, energy from the ATP and NADPH molecules generated by the light reactions drives a chemical pathway that uses the carbon in carbon dioxide (from the atmosphere) to build a three-carbon sugar called glyceraldehyde-3-phosphate (G3P). Cells then use G3P to build a wide variety of other sugars (such as glucose) and organic molecules. Many of these interconversions occur outside the chloroplast, following the transport of G3P from the stroma. The products of these reactions are then transported to other parts of the cell, including the mitochondria, where they are broken down to make more energy carrier molecules to satisfy the metabolic demands of the cell. In plants, some sugar molecules are stored as sucrose or starch.

This page appears in the following eBook

Topic rooms within Cell Biology

Within this Subject (25)

• Basic (25)

Other Topic Rooms

• Gene Inheritance and Transmission
• Gene Expression and Regulation
• Nucleic Acid Structure and Function
• Chromosomes and Cytogenetics
• Evolutionary Genetics
• Population and Quantitative Genetics
• Genes and Disease
• Genetics and Society
• Cell Origins and Metabolism
• Proteins and Gene Expression
• Subcellular Compartments
• Cell Communication
• Cell Cycle and Cell Division

© 2014 Nature Education

• Press Room |
• Terms of Use |
• Privacy Notice |

Visual Browse

• Why Does Water Expand When It Freezes
• Gold Foil Experiment
• Faraday Cage
• Oil Drop Experiment
• Magnetic Monopole
• Why Do Fireflies Light Up
• Types of Blood Cells With Their Structure, and Functions
• The Main Parts of a Plant With Their Functions
• Parts of a Flower With Their Structure and Functions
• Parts of a Leaf With Their Structure and Functions
• Why Does Ice Float on Water
• Why Does Oil Float on Water
• How Do Clouds Form
• What Causes Lightning
• How are Diamonds Made
• Types of Meteorites
• Types of Volcanoes
• Types of Rocks

Photosynthesis

What is photosynthesis.

It is the process by which green plants, algae, and certain bacteria convert light energy from the sun into chemical energy that is used to make glucose. The word ‘photosynthesis’ is derived from the Greek word phōs, meaning ‘light’ and synthesis meaning ‘combining together.’

Jan Ingenhousz, the Dutch-born British physician and scientist, discovered the process of photosynthesis.

Where does Photosynthesis Occur

Photosynthesis takes place mainly in the leaves of green plants and also in the stems of herbaceous plants as they also contain chlorophyll. Sometimes it also occurs in roots that contain chlorophyll like in water chestnut and Heart-leaved moonseed. Apart from plants, photosynthesis is also found to occur in blue-green algae.

What Happens During Photosynthesis

It involves a chemical reaction where water, carbon dioxide, chlorophyll, and solar energy are utilized as raw materials (inputs) to produce glucose, oxygen, and water (outputs).

Stages of the Process

Photosynthesis occurs in two stages:

1) The Light-dependent Reaction

• Takes place in the thylakoid membranes of chloroplasts only during the day in the presence of sunlight
• High-energy phosphate molecules adenosine triphosphate ( ATP ) and the reducing agent NADPH are produced with the help of electron transport chain

2) The Light-independent or Dark Reaction ( Calvin cycle )

• Takes place in the stroma of chloroplast in the absence of light that helps to fix carbon
• ATP and NADPH produced in the light reaction are utilized along with carbon dioxide to produce sugar in the form of glucose

Factors Affecting the Rate of Photosynthesis

• Intensity of Light: The higher intensity of light increases the rate of photosynthesis
• Temperature:  Warmer the temperature, higher the rate of photosynthesis. The rate is highest between the temperatures of 25° to 35° C, after which it starts to decrease
• Concentration of Carbon dioxide: Higher concentration of carbon dioxide increases the rate of photosynthesis until it reaches a certain point, beyond which no further effects are found   

Although all the above factors together interact to affect the rate of photosynthesis, each of them individually is also capable of directly influencing the process without the other factors and thus called limiting factors.

Importance of Photosynthesis

It serves two main purposes that are essential to support life on earth:

• Producing food for organisms that depend on others for their nutrition such as humans along with all other animals
• Synthesizing oxygen by replacing carbon dioxide in the atmosphere

Ans. Photosynthesis is an endothermic reaction because it absorbs the heat of the sun to carry out the process.

Ans. The oxygen in photosynthesis comes from splitting the water molecules.

Ans. Chlorophyll is the main light-absorbing pigment in photosynthesis.

Ans. The role of water is to provide oxygen in the form of oxygen gas to the atmosphere.

Ans. Sunlight is the source of energy that drives photosynthesis.

Ans. The easiest way to measure the rate of photosynthesis is to quantify the carbon dioxide or oxygen levels using a data logger. The rate of photosynthesis can also be measured by determining the increase in the plant ’s biomass (weight).

Ans. Photosynthesis is an energy-requiring process occurring only in green plants, algae, and certain bacteria that utilizes carbon dioxide and water to produce food in the form of carbohydrates. In contrast, cellular respiration is an energy-releasing process found in all living organisms where oxygen and glucose are utilized to produce carbon dioxide and water.

Ans. Glucose produced in photosynthesis is used in cellular respiration to make ATP.

Article was last reviewed on Tuesday, April 21, 2020

Related articles

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

Save my name, email, and website in this browser for the next time I comment.

Popular Articles

Join our Newsletter

Fill your E-mail Address

Related Worksheets

• Privacy Policy

© 2024 ( Science Facts ). All rights reserved. Reproduction in whole or in part without permission is prohibited.

• school Campus Bookshelves
• menu_book Bookshelves
• perm_media Learning Objects
• login Login
• how_to_reg Request Instructor Account
• hub Instructor Commons
• Download Page (PDF)
• Download Full Book (PDF)
• Periodic Table
• Physics Constants
• Scientific Calculator
• Reference & Cite
• Tools expand_more
• Readability

selected template will load here

This action is not available.

8.1: Overview of Photosynthesis - The Purpose and Process of Photosynthesis

• Last updated
• Save as PDF
• Page ID 13202

Learning Objectives

• Describe the process of photosynthesis

The Importance of Photosynthesis

The processes of all organisms—from bacteria to humans—require energy. To get this energy, many organisms access stored energy by eating food. Carnivores eat other animals and herbivores eat plants. But where does the stored energy in food originate? All of this energy can be traced back to the process of photosynthesis and light energy from the sun.

Photosynthesis is essential to all life on earth. It is the only biological process that captures energy from outer space (sunlight) and converts it into chemical energy in the form of G3P ( Glyceraldehyde 3-phosphate) which in turn can be made into sugars and other molecular compounds. Plants use these compounds in all of their metabolic processes; plants do not need to consume other organisms for food because they build all the molecules they need. Unlike plants, animals need to consume other organisms to consume the molecules they need for their metabolic processes.

The Process of Photosynthesis

During photosynthesis, molecules in leaves capture sunlight and energize electrons, which are then stored in the covalent bonds of carbohydrate molecules. That energy within those covalent bonds will be released when they are broken during cell respiration. How long lasting and stable are those covalent bonds? The energy extracted today by the burning of coal and petroleum products represents sunlight energy captured and stored by photosynthesis almost 200 million years ago.

Plants, algae, and a group of bacteria called cyanobacteria are the only organisms capable of performing photosynthesis. Because they use light to manufacture their own food, they are called photoautotrophs (“self-feeders using light”). Other organisms, such as animals, fungi, and most other bacteria, are termed heterotrophs (“other feeders”) because they must rely on the sugars produced by photosynthetic organisms for their energy needs. A third very interesting group of bacteria synthesize sugars, not by using sunlight’s energy, but by extracting energy from inorganic chemical compounds; hence, they are referred to as chemoautotrophs.

The importance of photosynthesis is not just that it can capture sunlight’s energy. A lizard sunning itself on a cold day can use the sun’s energy to warm up. Photosynthesis is vital because it evolved as a way to store the energy in solar radiation (the “photo-” part) as high-energy electrons in the carbon-carbon bonds of carbohydrate molecules (the “-synthesis” part). Those carbohydrates are the energy source that heterotrophs use to power the synthesis of ATP via respiration. Therefore, photosynthesis powers 99 percent of Earth’s ecosystems. When a top predator, such as a wolf, preys on a deer, the wolf is at the end of an energy path that went from nuclear reactions on the surface of the sun, to light, to photosynthesis, to vegetation, to deer, and finally to wolf.

• Photosynthesis evolved as a way to store the energy in solar radiation as high-energy electrons in carbohydrate molecules.
• Plants, algae, and cyanobacteria, known as photoautotrophs, are the only organisms capable of performing photosynthesis.
• Heterotrophs, unable to produce their own food, rely on the carbohydrates produced by photosynthetic organisms for their energy needs.
• photosynthesis : the process by which plants and other photoautotrophs generate carbohydrates and oxygen from carbon dioxide, water, and light energy in chloroplasts
• photoautotroph : an organism that can synthesize its own food by using light as a source of energy
• chemoautotroph : a simple organism, such as a protozoan, that derives its energy from chemical processes rather than photosynthesis

• More from M-W
• To save this word, you'll need to log in. Log In

photosynthesis

Definition of photosynthesis

Did you know.

Photosynthesis Has Greek Roots

The Greek roots of photosynthesis combine to produce the basic meaning "to put together with the help of light". Photosynthesis is what first produced oxygen in the atmosphere billions of years ago, and it's still what keeps it there. Sunlight splits the water molecules (made of hydrogen and oxygen) held in a plant's leaves and releases the oxygen in them into the air. The leftover hydrogen combines with carbon dioxide to produce carbohydrates, which the plant uses as food—as do any animals or humans who might eat the plant.

Examples of photosynthesis in a Sentence

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'photosynthesis.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

1898, in the meaning defined above

Dictionary Entries Near photosynthesis

photosynthate

photosynthetic ratio

Cite this Entry

“Photosynthesis.” Merriam-Webster.com Dictionary , Merriam-Webster, https://www.merriam-webster.com/dictionary/photosynthesis. Accessed 21 Apr. 2024.

Kids Definition

Kids definition of photosynthesis, medical definition, medical definition of photosynthesis, more from merriam-webster on photosynthesis.

Nglish: Translation of photosynthesis for Spanish Speakers

Britannica.com: Encyclopedia article about photosynthesis

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

Can you solve 4 words at once?

Word of the day, noblesse oblige.

See Definitions and Examples »

Get Word of the Day daily email!

Popular in Grammar & Usage

Your vs. you're: how to use them correctly, every letter is silent, sometimes: a-z list of examples, more commonly mispronounced words, how to use em dashes (—), en dashes (–) , and hyphens (-), absent letters that are heard anyway, popular in wordplay, the words of the week - apr. 19, 10 words from taylor swift songs (merriam's version), a great big list of bread words, 10 scrabble words without any vowels, 12 more bird names that sound like insults (and sometimes are), games & quizzes.

What is photosynthesis?

Photosynthesis is the process plants, algae and some bacteria use to turn sunlight, carbon dioxide and water into sugar and oxygen.

• Photosynthetic processes
• Photosynthesis equation
• The carbon exchange
• How do plants absorb sunlight?
• Location of photosynthesis

Light-dependent reactions

• The Calvin cycle

Types of photosynthesis

Additional resources.

Photosynthesis is the process used by plants, algae and some bacteria to turn sunlight into energy. The process chemically converts carbon dioxide (CO2) and water into food (sugars) and oxygen . The chemical reaction often relies on a pigment called chlorophyll, which gives plants their green color.  Photosynthesis is also the reason our planet is blanketed in an oxygen-rich atmosphere.

Types of photosynthetic processes

There are two types of photosynthesis: oxygenic and anoxygenic. They both follow very similar principles, but the former is the most common and is seen in plants, algae and cyanobacteria. 

During oxygenic photosynthesis, light energy transfers electrons from water (H2O) taken up by plant roots to CO2 to produce carbohydrates . In this transfer, the CO2 is "reduced," or receives electrons, and the water is "oxidized," or loses electrons. Oxygen is produced along with carbohydrates.

This process creates a balance on Earth, in which the carbon dioxide produced by breathing organisms as they consume oxygen in respiration is converted back into oxygen by plants, algae and bacteria.

Anoxygenic photosynthesis, meanwhile, uses electron donors that are not water and the process does not generate oxygen, according to "Anoxygenic Photosynthetic Bacteria" by LibreTexts . The process typically occurs in bacteria such as green sulfur bacteria and phototrophic purple bacteria. 

The Photosynthesis equation

Though both types of photosynthesis are complex, multistep affairs, the overall process can be neatly summarized as a chemical equation.

The oxygenic photosynthesis equation is: 

6CO2 + 12H2O + Light Energy → C6H12O6 + 6O2 + 6H2O

Here, six molecules of carbon dioxide (CO2) combine with 12 molecules of water (H2O) using light energy. The end result is the formation of a single carbohydrate molecule (C6H12O6, or glucose) along with six molecules each of oxygen and water.

Similarly, the various anoxygenic photosynthesis reactions can be represented as a single generalized formula:

CO2 + 2H2A + Light Energy → [CH2O] + 2A + H2O

The letter A in the equation is a variable, and H2A represents the potential electron donor. For example, "A" may represent sulfur in the electron donor hydrogen sulfide (H2S), according to medical and life sciences news site News Medical Life Sciences . 

How is carbon dioxide and oxygen exchanged?

Plants absorb CO2 from the surrounding air and release water and oxygen via microscopic pores on their leaves called stomata. 

When stomata open, they let in CO2; however, while open, the stomata release oxygen and let water vapor escape. Stomata close to prevent water loss, but that means the plant can no longer gain CO2 for photosynthesis. This tradeoff between CO2 gain and water loss is a particular problem for plants growing in hot, dry environments. 

How do plants absorb sunlight for photosynthesis?

Plants contain special pigments that absorb the light energy needed for photosynthesis.

Chlorophyll is the primary pigment used for photosynthesis and gives plants their green color, according to science education site Nature Education . Chlorophyll absorbs red and blue light and reflects green light. Chlorophyll is a large molecule and takes a lot of resources to make; as such, it breaks down towards the end of the leaf's life, and most of the pigment's nitrogen (one of the building blocks of chlorophyll) is resorbed back into the plant,  When leaves lose their chlorophyll in the fall, other leaf pigments such as carotenoids and anthocyanins begin to show. While carotenoids primarily absorb blue light and reflect yellow, anthocyanins absorb blue-green light and reflect red light, according to Harvard University's The Harvard Forest .

Pigment molecules are associated with proteins, which allow them the flexibility to move toward light and toward one another. A large collection of 100 to 5,000 pigment molecules constitutes an "antenna," according to an article by Wim Vermaas , a professor at Arizona State University. These structures effectively capture light energy from the sun, in the form of photons.

The situation is a little different for bacteria. While cyanobacteria contain chlorophyll, other bacteria, for example, purple bacteria and green sulfur bacteria, contain bacteriochlorophyll to absorb light for anoxygenic photosynthesis, according to " Microbiology for Dummies " (For Dummies, 2019). 

Related: What if humans had photosynthetic skin?

Where in the plant does photosynthesis take place?

Photosynthesis occurs in chloroplasts, a type of plastid (an organelle with a membrane) that contains chlorophyll and is primarily found in plant leaves. 

Chloroplasts are similar to mitochondria , the energy powerhouses of cells, in that they have their own genome, or collection of genes, contained within circular DNA. These genes encode proteins that are essential to the organelle and to photosynthesis.

Inside chloroplasts are plate-shaped structures called thylakoids that are responsible for harvesting photons of light for photosynthesis, according to the biology terminology website Biology Online . The thylakoids are stacked on top of each other in columns known as grana. In between the grana is the stroma — a fluid containing enzymes, molecules and ions, where sugar formation takes place. 

Ultimately, light energy must be transferred to a pigment-protein complex that can convert it to chemical energy, in the form of electrons. In plants, light energy is transferred to chlorophyll pigments. The conversion to chemical energy is accomplished when a chlorophyll pigment expels an electron, which can then move on to an appropriate recipient. 

The pigments and proteins that convert light energy to chemical energy and begin the process of electron transfer are known as reaction centers.

When a photon of light hits the reaction center, a pigment molecule such as chlorophyll releases an electron.

The released electron escapes  through a series of protein complexes linked together, known as an electron transport chain. As it moves through the chain, it generates the energy to produce ATP (adenosine triphosphate, a source of chemical energy for cells) and NADPH — both of which are required in the next stage of photosynthesis in the Calvin cycle. The "electron hole" in the original chlorophyll pigment is filled by taking an electron from water. This splitting of water molecules releases oxygen into the atmosphere.

Light-independent reactions: The Calvin cycle

The Calvin cycle is the three-step process that generates sugars for the plant, and is named after Melvin Calvin , the Nobel Prize -winning scientist who discovered it decades ago. The Calvin cycle uses the ATP and NADPH produced in chlorophyll to generate carbohydrates. It takes plate in the plant stroma, the inner space in chloroplasts.

In the first step of this cycle, called carbon fixation, an enzyme called RuBP carboxylase/oxygenase, also known as rubiso, helps incorporate CO2 into an organic molecule called 3-phosphoglyceric acid (3-PGA). In the process, it breaks off a phosphate group on six ATP molecules to convert them to ADP, releasing energy in the process, according to LibreTexts.

In the second step, 3-PGA is reduced, meaning it takes electrons from six NADPH molecules and produces two glyceraldehyde 3-phosphate (G3P) molecules.

One of these G3P molecules leaves the Calvin cycle to do other things in the plant. The remaining G3P molecules go into the third step, which is regenerating rubisco. In between these steps, the plant produces glucose, or sugar.

Three CO2 molecules are needed to produce six G3P molecules, and it takes six turns around the Calvin cycle to make one molecule of carbohydrate, according to educational website Khan Academy.

There are three main types of photosynthetic pathways: C3, C4 and CAM. They all produce sugars from CO2 using the Calvin cycle, but each pathway is slightly different.

C3 photosynthesis

Most plants use C3 photosynthesis, according to the photosynthesis research project Realizing Increased Photosynthetic Efficiency (RIPE) . C3 plants include cereals (wheat and rice), cotton, potatoes and soybeans. This process is named for the three-carbon compound 3-PGA that it uses during the Calvin cycle. 

C4 photosynthesis

Plants such as maize and sugarcane use C4 photosynthesis. This process uses a four-carbon compound intermediate (called oxaloacetate) which is converted to malate , according to Biology Online. Malate is then transported into the bundle sheath where it breaks down and releases CO2, which is then fixed by rubisco and made into sugars in the Calvin cycle (just like C3 photosynthesis). C4 plants are better adapted to hot, dry environments and can continue to fix carbon even when their stomata are closed (as they have a clever storage solution), according to Biology Online. 

CAM photosynthesis

Crassulacean acid metabolism (CAM) is found in plants adapted to very hot and dry environments, such as cacti and pineapples, according to the Khan Academy. When stomata open to take in CO2, they risk losing water to the external environment. Because of this, plants in very arid and hot environments have adapted. One adaptation is CAM, whereby plants open stomata at night (when temperatures are lower and water loss is less of a risk). According to the Khan Academy, CO2 enters the plants via the stomata and is fixed into oxaloacetate and converted into malate or another organic acid (like in the C4 pathway). The CO2 is then available for light-dependent reactions in the daytime, and stomata close, reducing the risk of water loss. 

Discover more facts about photosynthesis with the educational science website sciencing.com . Explore how leaf structure affects photosynthesis with The University of Arizona . Learn about the different ways photosynthesis can be measured with the educational science website Science & Plants for Schools .  

This article was updated by Live Science managing editor Tia Ghose on Nov. 3, 2022.

Sign up for the Live Science daily newsletter now

Get the world’s most fascinating discoveries delivered straight to your inbox.

Daisy Dobrijevic joined  Space.com  in February 2022 as a reference writer having previously worked for our sister publication  All About Space  magazine as a staff writer. Before joining us, Daisy completed an editorial internship with the BBC Sky at Night Magazine and worked at the  National Space Centre  in Leicester, U.K., where she enjoyed communicating space science to the public. In 2021, Daisy completed a PhD in plant physiology and also holds a Master's in Environmental Science, she is currently based in Nottingham, U.K.

Are kale, broccoli and Brussels sprouts really all the same plant?

390 million-year-old fossilized forest is the oldest ever discovered

East Africa's Lake Nakuru almost doubled in size in 13 years — and that's bad news for flamingos

Most Popular

• 2 James Webb telescope confirms there is something seriously wrong with our understanding of the universe
• 3 'Exceptional' prosthesis of gold, silver and wool helped 18th-century man live with cleft palate
• 4 NASA spacecraft snaps mysterious 'surfboard' orbiting the moon. What is it?
• 5 AI pinpoints where psychosis originates in the brain
• 2 NASA's downed Ingenuity helicopter has a 'last gift' for humanity — but we'll have to go to Mars to get it
• 3 2,500-year-old skeletons with legs chopped off may be elites who received 'cruel' punishment in ancient China
• 4 Modern Japanese people arose from 3 ancestral groups, 1 of them unknown, DNA study suggests
• 5 The universe may be dominated by particles that break causality and move faster than light, new paper suggests

Learn about Photosynthesis

Very few plants can actually trap their own food and none can go grocery shopping so plants need to make their food by themselves if they want to eat!

What has the sun got to do with photosynthesis?

The sun is a very powerful source of energy. People are always trying to harness it to make electricity, warm their houses, heat their water etc. Plants figured out how to use solar energy millions of years ago to make their food. They use the light energy from the sun (solar energy) and convert it into chemical energy that is stored as sugar (glucose) in the plant. Excess glucose is stored as starch in the leaves, roots, stems and seeds of the plant. The energy from the sun is transferred to the plants. This energy is then passed to animals when they eat plants. Whenever the plant needs energy it breaks down its stored glucose for its life processes

How do plants capture the sun’s energy?

Why are most leaves broad and flat?

What else is important to help plants grow?

Just like humans do, plants also need mineral nutrients to keep healthy, grow and perform their life processes well. Plants get mineral nutrients from the soil using their roots. The mineral nutrients are dissolved in the water the plant absorbs. If the soil does not have enough mineral nutrients the plant will not grow properly. Farmers often test the soil to check that there are enough nutrients for their crops to grow. If there are not enough minerals present in the soil the farmer will add fertilizers. A fertilizer usually contains the main minerals that a plant needs.

Why is photosynthesis so important?

Photosynthesis is one of the most important chemical reactions in the world. What are the reasons for this? Photosynthesis makes food for plants and for animals. We have already learned that plants feed themselves by using sunlight to convert carbon dioxide and water into food (sugar). Whenever the plant needs energy for itself it breaks down its stored food. Animals get their food by eating the plants so they depend on plants for their food. Photosynthesis results in oxygen gas being made that is released by the plant into the atmosphere for living things to breathe. Living things breathe in oxygen and breathe out carbon dioxide all the time. Fortunately plants do the opposite. When plants are making food they breathe in carbon dioxide and breathe out oxygen. Therefore plants are extremely important to humans and animals as they give them oxygen to breathe and prevent us all from suffocating. Oxygen is needed by all living organisms to burn up food for energy. Photosynthesis results in carbon dioxide gas being removed from the atmosphere. Carbon dioxide is a greenhouse gas that is responsible for global warming.

• Biology Article
• What is Photosynthesis

What Is Photosynthesis?

“Photosynthesis is the process used by green plants and a few organisms that use sunlight, carbon dioxide and water to prepare their food.”

The process of photosynthesis is used by plants, algae and certain bacteria that convert light energy into chemical energy. The glucose formed during the process of photosynthesis provides two important resources to organisms: energy and fixed carbon.

Read on to explore what is photosynthesis and the processes associated with it.

Site of Photosynthesis

Photosynthesis takes place in special organelles known as chloroplast. This organelle has its own DNA, genes and hence can synthesize its own proteins. Chloroplasts consist of stroma, fluid, and stack of thylakoids known as grana. There are three important pigments present in the chloroplast that absorb light energy, chlorophyll a, chlorophyll b, and carotenoids.

Also Read: Photosynthesis Process

Types of Photosynthesis

There are two different types of photosynthesis:

• Oxygenic photosynthesis
• Anoxygenic photosynthesis

Oxygenic Photosynthesis

Oxygenic photosynthesis is more common in plants, algae and cyanobacteria. During this process, electrons are transferred from water to carbon dioxide by light energy, to produce energy. During this transfer of electrons, carbon dioxide is reduced while water is oxidized, and oxygen is produced along with carbohydrates.

During this process, plants take in carbon dioxide and expel oxygen into the atmosphere.

This process can be represented by the equation:

6CO2+ 12H2O + LIGHT ENERGY → C6H12O6 + 6O2 + 6H2O

Anoxygenic Photosynthesis

This type of photosynthesis is usually seen in certain bacteria, such as green sulphur bacteria and purple bacteria which dwell in various aquatic habitats. Oxygen is not produced during the process.

The anoxygenic photosynthesis can be represented by the equation:

CO2 + 2H2A + LIGHT ENERGY → [CH2O] + 2A + H2O

Also Read:  Difference between Photosynthesis and Respiration

Photosynthesis Apparatus

The photosynthesis apparatus includes the following essential components:

Pigments not only provide colour to the photosynthetic organisms, but are also responsible for trapping sunlight. The important pigments associated with photosynthesis include:

• Chlorophyll: It is a green-coloured pigment that traps blue and red light. Chlorophyll is subdivided into, “chlorophyll a”, “chlorophyll b”, and “chlorophyll c”. “Chlorophyll a” is widely present in all the photosynthetic cells. A bacterial variant of chlorophyll known as bacteriochlorophyll can absorb infrared rays .
• Carotenoids: These are yellow, orange or red-coloured pigments that absorb bluish-green light. Xanthophyll and carotenes are examples of carotenoids.
• Phycobilins: These are present in bacteria and red algae . These are red and blue pigments that absorb wavelength of light that are not properly absorbed by carotenoids and chlorophyll.

Plastids are organelles found in the cytoplasm of eukaryotic photosynthetic organisms. They contain pigments and can also store nutrients. Plastids are of three types:

• Leucoplast: These are colourless, non-pigmented and can store fats and starch.
• Chromoplasts: They contain carotenoids.
• Chloroplasts: These contain chlorophyll and are the site of photosynthesis.

Antennae is the collection of 100 to 5000 pigment molecules that capture light energy from the sun in the form of photons. The light energy is transferred to a pigment-protein complex that converts light energy to chemical energy.

Reaction Centers

The pigment-protein complex responsible for the conversion of light energy to chemical energy forms the reaction centre.

Also Read: Photosynthesis

To know more about what is photosynthesis and other topics related to it, keep visiting BYJU’S website or download BYJU’S app for further reference.

Put your understanding of this concept to test by answering a few MCQs. Click ‘Start Quiz’ to begin!

Select the correct answer and click on the “Finish” button Check your score and answers at the end of the quiz

Visit BYJU’S for all Biology related queries and study materials

Your result is as below

Request OTP on Voice Call

Leave a Comment Cancel reply

Your Mobile number and Email id will not be published. Required fields are marked *

Post My Comment

• Share Share

Register with BYJU'S & Download Free PDFs

Register with byju's & watch live videos.

Biosynthesis

Biosynthesis n., plural: biosyntheses [ˈbaɪəʊˈsɪnθəsɪs] Definition: Biological production of molecules within living organisms

Table of Contents

Biosynthesis Definition

Biosynthesis refers to the production (synthesis) of a complex chemical compound from simpler precursors in a living organism , usually involving key enzymes to catalyze the reaction and energy sources.  The creation of an organic compound in a living organism, especially at the molecular level, is referred to as biosynthesis. It involves the orchestrated series of enzymatic reactions within biosynthetic pathways to create intricate molecules essential for life and human health.

Examples of Biosynteses

Biosynthesis involves different biological processes that utilize specific chemical reactions to produce essential complex molecules within living organisms.  Examples are as follows:

• Photosynthesis is the synthesis of complex products using carbon dioxide , water , inorganic salts, and light energy (from sunlight) captured by chlorophyll and other accessory pigments. This process occurs in photoautotrophic organisms — from single-celled cyanobacteria  to multicellular organisms, such as plants .
• Carbohydrate synthesis is the synthesis of simple sugars and complex carbohydrates.
• Amino acid synthesis is the synthesis of an amino acid , which in turn is used in the synthesis of proteins and peptides , as well as other amino acids (which serve as precursors for certain amino acids).
• Protein synthesis is the synthesis of proteins , including catalytic enzymes. This process is closely linked to amino acid synthesis as amino acids are the building blocks of proteins.
• Lipid synthesis is the synthesis of lipids , such as fatty acids and phospholipids (for the synthesis of lipid membranes).
• Nucleic acid synthesis is the biosynthesis of nucleic acids , such as DNA and RNA . Nucleic acids carry the genes encoding the correct sequence of amino acids of a particular protein.
• ATP synthesis is a biosynthetic process, which is tightly linked to the energy-producing, enzyme-catalyzed reactions of cellular respiration , such as glycolysis , Krebs Cycle , electron transport chain , and chemiosmotic coupling .

Energy Driving Biosyntheses

Energy drives chemical reactions that produce new substances. The major forms of energy utilized are chemical energy (particularly ATP and other energy carriers like GTP and NADPH ) and light energy .

Acetyl-CoA is a pivotal molecule in the biosynthesis of most organisms. It acts as a vital intermediate connecting catabolic and anabolic processes of cellular metabolism . For instance, it acts as a precursor for the synthesis of natural products (e.g., fatty acids and cholesterol). In cellular respiration, two acetyl-CoA molecules can enter the Krebs cycle (where foodstuffs are fully oxidized and processed at the cellular level) from the two molecules of pyruvate formed during the initial reaction ( glycolysis ).

• 5.12B: Biosynthesis and Energy . (2017, May 9). Biology LibreTexts. https://bio.libretexts.org/Bookshelves/Microbiology/Microbiology_(Boundless)/05%3A_Microbial_Metabolism/5.12%3A_Biosynthesis/5.12B%3A_Biosynthesis_and_Energy

©BiologyOnline.com. Content provided and moderated by Biology Online Editors.

Last updated on August 25th, 2023

You will also like...

Water in Plants

The movement of molecules (specifically, water and solutes) is vital to the understanding of plant processes. This tuto..

Gene Regulation in Eukaryotes

Learn about the general structure of a eukaryotic gene, the transcription factors, and post-transcriptional regulation....

Birth Control and Contraception

Different pregnancy and birth control and contraception strategies are described. Read this tutorial to learn each of th..

Selective Breeding

Gregor Mendel's studies into Monohybrid and Dihybrid crossing and Charles Darwin's study of evolution and natural select..

The sea was teeming with life. Eventually, through reproduction and continued variation, fish came about. There are over..

Gene Action – Operon Hypothesis

Related articles....

No related articles found

What is the definition of photosynthesis?

Table of Contents

Concept of photosynthesis

Photosynthesis is a physiological process of plants. In 1898, scientist Barnes first used the term photosynthesis. Photosynthesis comes from two Greek words ‘photo’ means light, and ‘synthesis’ means, synthesize, or produce. Therefore, photosynthesis is the synthesis or production of any element with the help of light. In photosynthesis, solar energy from the sun is bound to glucose in the form of chemical energy. It is also a type of autotrophic nutrition . This energy is used in the biological work of plants. Other organisms absorb this energy directly or indirectly through food and use it to survive. That means the presence of living things on Earth depends on photosynthesis (1) & (3) .

The physiological process by which cells use chlorophyll and other pigments in the biochemical reaction of water and CO₂ taken from the environment to bind the solar energy to synthesize glucose and produce water and oxygen as by-products are called photosynthesis. In a word, the technique of making food for plants in the presence of sunlight is called photosynthesis. The chemical equation of photosynthesis is

6CO₂ + 12H₂O → C₆H₁₂O₆ + 6O₂ + 6H₂O (1) .

Site of photosynthesis

Fig: leaf structure

Photosynthesis occurs in all green chlorophyll-pigmented cells. Since plants contain mainly chlorophyll, photosynthesis occurs primarily in plants. The mesophyll tissue of the leaf is the ideal place for photosynthesis. This is because the leaves can absorb more sunlight as they are flattened and stretched.  Mesophyll tissue cells have the highest number of chloroplasts and the highest amount of stomata, they are ideal for photosynthesis. Photosynthesis occurs on the young green stems of plants, on the green aerial roots of orchids, bodies of euglena, chrysamoeba, etc (2) .

Components of photosynthesis and their roles

The main components of photosynthesis are water, carbon dioxide, chlorophyll, and sunlight. There are also some other components like NADP, ADP, RuBP, etc. But among all these elements water, CO₂, chlorophyll, and sunlight play an important role in photosynthesis. (2) & (3)

Visible light is a part of the waves that constantly reach the Earth’s surface from space. This visible light of the sun is used in photosynthesis. It is actually made up of some tiny energy particles. These are called photon particles. These photos are used in photosynthesis. The sun is the main source of sunlight. Photosynthesis can also occur in artificial light.

• Sunlight helps activate chlorophyll.
• Sunlight produces high-potency ATP by photophosphorylation in the cell and releases oxygen into the water.
• Assists in photolysis (2) & (3) .

Chlorophyll

Chloroplasts present in leaf mesophyll tissue are the main source of chlorophyll. Chlorophyll is found in the grana area of chloroplasts.

• Chlorophyll is excited by absorbing photons of sunlight and breaks down water into hydrogen and hydroxyl ions.
• The electrons emitted from the active chlorophyll produce ATP in a light chemical process. (2) & (3) .

Terrestrial plants absorb water from the soil through the roots. Aquatic plants absorb water from reservoirs by their submerged parts. Parasitic plants absorb water vapor from the air by gaseous roots. Environmental water is the source of water required for the photosynthesis of plants.

• Water is used as a raw material in photosynthesis.
• Water provides electrons to chlorophyll during photosynthesis.
• In dark reactions, the hydrogen needed to oxidize CO₂ is produced by water analysis.
• Water is also the source of the oxygen that is produced in photosynthesis (2) & (3) .

Carbon dioxide

Terrestrial and parasitic plants absorb CO₂ from the atmosphere through the stomata. Aquatic plants absorb CO₂ dissolved in water by their submerged parts.

• CO₂ is a raw material of photosynthesis.
• Carbon assimilation occurs with carbon dioxide.
• The source of carbon in glucose produced by photosynthesis is carbon dioxide (2) & (3) .

Mechanism of photosynthesis

Photosynthesis is done in two steps

• Light reaction
• Light-independent phase or carbon reaction.

1. Light reaction

This is the first stage of photosynthesis. The presence of sunlight is essential at this stage. This reaction occurs in the grana area of the chloroplast. Sunlight, water, chlorophyll, and other pigments, NADP, and ADP are essential components of this reaction (1) & (2) . It involves the following process.

a. Activation of chlorophyll

The chlorophyll in the leaves is excited and activated by absorbing photons of sunlight. This causes the excited chlorophyll to release electrons.

b. Photolysis

This active chlorophyll breaks down water into hydrogen ions (H⁺) and hydroxyl ions (OH⁻). The effect of sunlight on the analysis of two ions in water in this way is called photolysis. In 1940, scientist Robin Hill first observed this process. Hence, as its name implies, this reaction is called hill reaction.

c. Reduction of NADP & NADPH creation

The hydrogen ions (H⁺) produced in the analysis of water combine with the hydrogen receptor NADP present in the leaf to form the NADPH. In this case, NADP acts as a hydrogen receptor. So it is called hill reagent. (1) & (2)

NADP + 2H⁺ + 2e⁻ → NADPH + H⁺

d. Oxygen emissions

The hydroxyl ion (OH⁻), another element formed in the analysis of water, leaves the electron to form the OH radical. The four OH radicals combine to form two atoms of water and one atom of oxygen. The water generated is used for the needs of plants and oxygen is released into the atmosphere through the stomata.

4OH⁻ – 4e⁻ → 4[OH];   4[OH] → 2H₂O + O₂ ↑

e. Photophosphorylation

Photophosphorylation is the process where adenosine diphosphate (ADP) present in the leaves combines with inorganic phosphate (Pi) in the presence of sunlight to form high-potency adenosine triphosphate (ATP) (1) & (2) .

ADP + Pi   →     ATP

2. Light-independent phase or carbon reaction

This is the second stage of photosynthesis. This process occurs in the stroma of the chloroplast. This reaction does not require light, so this phase was formerly called the dark reaction. But even if the light is not used directly in this phase, the reactions depend on the substance produced in the light phase. So this phase is now called the light-independent phase. Scientist Blackman first noticed the reactions at this stage. That is why it’s called the Blackman reaction. The necessary components in this phase are CO₂, ATP, and NADPH (1) & (2) .  It involves the following process.

a. Carbon assimilation

It is the process where atmospheric CO₂ enters the leaf through stomata and reacts with the ribulose bisphosphate (RuBP) in the presence of an enzyme called RuBisCO inside the mesophyll tissue to form phosphoglyceric acid (PGA).

6CO₂ + 6RuBP → 12PGA

b. Phosphoglyceraldehyde

Then phosphoglyceraldehyde (PGAld) is formed when ATP and NADPH+ H⁺ react with PGA.

12PGA + 12 (NADPH + H⁺) + 12ATP → 12 PGAld + 12NADP⁺ + 12ADP + 12Pi

c. Reproduction of RuBP

Out of the 12 molecules, PGAld, 10 molecules of PGAld produce 6 molecules of RuBP through several chemical reactions. Thus the Calvin cycle continues in cycles.

d. Glucose synthesis

Glucose is produced in chloroplasts in a few steps from the remaining 2 molecules of 12 molecules PGAld.

2PGAld → C₆H₁₂O₆ (glucose)

Most of the glucose produced is transported to the plant body as sucrose food. The rest of the glucose is stored in the form of starch in various parts of the plant.

Photosynthesis controlling factors

External factors.

Photosynthesis depends on the intensity, nature, and duration of the light. When the intensity of light is high, the process is disrupted.

2. Carbon dioxide (CO ₂)

As the amount of CO₂ in the air increases by 0.01%, the number of photosynthesis increases.

When a certain amount of water is deficient, the cells that control the stomata and the chloroplast lose performance. As a result, the process is interrupted.

4. Temperature

Photosynthesis rates typically increase from 25°C to 37°C. At high temperatures, the enzyme action is lost.

5. Oxygen (O ₂)

As the oxygen in the air increases, the rate of photosynthesis decreases.

6. Leaf age

As the leaf age of the plant increases, the rate of photosynthesis of that leaf decreases (1) .

Internal factors

1. chlorophyll.

The process of photosynthesis depends on the activity of chlorophyll.

The rate of photosynthesis depends on the presence of different types of enzymes.

3. Protoplasm

The protoplasm indirectly controls the photosynthesis process.

4. Accumulation of photosynthetic substances

The rate of photosynthesis decreases when photosynthetic substances accumulate in mesophyll tissue cells.

5. Leaf structure

This process is largely dependent on the internal structure of the leaf (1) .

Importance of photosynthesis

1. source of energy.

In the process of photosynthesis, solar energy is converted into chemical energy first bound to the ATP molecule, and is stored as potential energy in the food produced. Thus only photosynthesis is capable of converting solar energy and storing energy in food.

2. Source of food

Photosynthesis is the main source of food for all living things. The glucose produced in this process is converted into starch and is stored in various parts of the plant as future food.

3. Maintaining the balance of O ₂ & CO ₂

The photosynthesis process maintains the balance of oxygen and carbon dioxide in the atmosphere. The normal amount of O₂ in the atmosphere is 20 to 60% and the normal amount of CO₂ is 0.03%. Fauna takes in O₂ from the environment during respiration and releases CO₂. As a result, the amount of O₂ is decreased and the amount of CO₂ is increased in the atmosphere. Plants absorb CO₂ during photosynthesis and release O₂ to balance the two gases in the atmosphere.

4. Role in the progress of human civilization

The plant provides food, wood, coal, paper, textiles, herbal medicines, etc. Thus the contribution of photosynthesis to human welfare and the development of human civilization is immense (2) .

Why photosynthesis is called anabolism?

The process by which the dry weight of an organism increases is called anabolic reaction. In the process of photosynthesis, simple compounds (H₂O and CO₂) produce complex compounds (glucose). As a result, the dry weight of the plant body protoplasm increases. Therefore, it is called anabolism.

Why photosynthesis is called an oxidation-reduction reaction?

In the light phase of photosynthesis, water is oxidized to produce O₂. And in the light-independent phase, glucose is produced when CO₂ is reduced. For this reason, photosynthesis is called an oxidation-reduction reaction.  

Comments are closed.

• Cambridge Dictionary +Plus

Meaning of photosynthesis in English

Your browser doesn't support HTML5 audio

• chasmogamous
• cleistogamous
• efflorescence
• in flower idiom
• multi-headed
• palynological

Related word

Photosynthesis | american dictionary, examples of photosynthesis, translations of photosynthesis.

Get a quick, free translation!

Word of the Day

have irons in the fire

to be involved with many activities or jobs at the same time or to make certain that there are always several possibilities available

Binding, nailing, and gluing: talking about fastening things together

Learn more with +Plus

• Recent and Recommended {{#preferredDictionaries}} {{name}} {{/preferredDictionaries}}
• Definitions Clear explanations of natural written and spoken English English Learner’s Dictionary Essential British English Essential American English
• Grammar and thesaurus Usage explanations of natural written and spoken English Grammar Thesaurus
• Pronunciation British and American pronunciations with audio English Pronunciation
• English–Chinese (Simplified) Chinese (Simplified)–English
• English–Chinese (Traditional) Chinese (Traditional)–English
• English–Dutch Dutch–English
• English–French French–English
• English–German German–English
• English–Indonesian Indonesian–English
• English–Italian Italian–English
• English–Japanese Japanese–English
• English–Norwegian Norwegian–English
• English–Polish Polish–English
• English–Portuguese Portuguese–English
• English–Spanish Spanish–English
• English–Swedish Swedish–English
• Dictionary +Plus Word Lists
• English    Noun
• American    Noun
• Translations
• All translations

Add photosynthesis to one of your lists below, or create a new one.

{{message}}

Something went wrong.

There was a problem sending your report.