How Photosynthesis Supports Life and Food Chains
What is the Site of Photosynthesis?
Chlorophyll present in the plants makes the plant look green, which is present in chloroplasts. Hence, a chloroplast is the site of photosynthesis. A standard chloroplast is of discoid shape in the plants.
All green parts of a plant take part in the process of photosynthesis. Let's say if the stem of a plant is green, it will perform the photosynthesis process as well. But out of all of the parts, the leaves play the most significant organs of photosynthesis. So, leaves are recognised as the food factories of green plants because photosynthesis process takes place in them. Just one square millimetre of a leaf consists of a half a million chloroplasts in it. It means around 4 - 6 micron.
About Site of Photosynthesis - Chloroplasts
All plants, algae, and certain microorganisms perform this important photosynthesis process. Photosynthesis reaction happens specifically, in the grana and stroma regions of chloroplasts. The stroma includes circular RNA, DNA, and enzymes that help in starch synthesis in plants. This stroma also consists of many grana, and each granum holds many disc-shaped membranes. These disc-shaped structures look like a stack of coins and are called thylakoids. One chloroplast has 40 to 60 grana. In this grana, photosynthetic pigments are present.
Photosynthesis Process
Many of us think that we are feeding the plant by putting the soil in a plant, exposing it to the sun, and watering it. However, the reality is different; these sources are not real foods for plants.
Plants are also scientifically known as autotrophs because they are capable of utilising energy from light to synthesise. In this way, plants can produce their own food called starch or glucose. The plants make glucose by using water, sunlight, and the gases present in the atmosphere. This glucose is a kind of sugar that helps plants to stay alive. In return, plants release oxygen in the environment that is a byproduct of photosynthetic reactions.
This whole process of converting light energy into chemical energy is called photosynthesis. In simple terms, photosynthesis absorbs carbon dioxide and emits oxygen in the air. Thus, photosynthesis helps in the maintenance of carbon dioxide and oxygen balance in the environment too.
Importance of Photosynthesis in Life
Without photosynthesis, life on the Earth can come to hold as it plays one of the most crucial roles in the lifecycle of plants. It is vital for the survival of the large majority of life in the world. Through this process, practically every kind of energy found in the biosphere becomes accessible to living organisms. It is the base of Earth's food source that is consumed directly or indirectly by all living things. Furthermore, the oxygen we get to breathe from the atmosphere comes because of the photosynthesis process.
Hence, no photosynthesis can lead to little to no food, and the majority of the organisms would disappear from the Earth as eventually there will be no oxygen gas in the environment.
Food Production in Plants
Leaves comprise a lot of tiny pore-like structures in their below surface that are called stomata. The leaves absorb carbon dioxide from the air through the stomata. Further, hair-like pipelines present in the roots and all through the plant help to transport water and minerals in it. These pipelines are a type of tissues called xylem.
A green pigment called chlorophyll is found in the site of photosynthesis - chloroplast that absorbs sunlight and produces energy. Carbohydrate produced acts as food for plants that eventually turns into starch and stores in leaves. Thus, starch is a kind of carbohydrate. Further, the starch transports from leaves to other parts of a plant. Also, oxygen emits in the air through stomata during this process.
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(Plant using sunlight, water and carbon dioxide during photosynthesis to produce carbohydrate and oxygen.)
Equation of Photosynthesis Process
The photosynthesis process is supposed to be an endothermic reaction. Water and carbon dioxide are the two reactants involved in the photosynthesis reaction that produces two products, i.e., glucose as well as oxygen.
Here is an equation for photosynthesis
6CO2 + 6H2O→ C6H12O6 + 6O2
Types of Photosynthesis
There are two types of photosynthesis whose general principles regarding the photosynthetic process are quite the same. Let's know about them and what makes them different from each other.
Oxygenic Photosynthesis
Oxygenic photosynthesis is widely seen in plants, cyanobacteria, and algae. It is one of those types of photosynthesis that counterbalances the respiratory system of the environment. The oxygenic photosynthesis uses the carbon dioxide created in the atmosphere by all breathing organisms and releases oxygen into it.
In this reaction, electrons from water (H2O) are transformed by the light energy into carbon dioxide (CO2). As a result, plants produce carbohydrates. During this transfer process, the water gets oxidised or loses electrons, and carbon dioxide diminishes or receives electrons. Thus, oxygen and carbohydrates are produced.
The chemical equation for oxygenic photosynthesis is
6CO2 + 12H2O + Light Energy → C6H12O6 + 6O2 + 6H2O
Anoxygenic Photosynthesis
In the anoxygenic photosynthetic process, electron donors are used along with water. This type of photosynthesis reaction is generally found in microorganisms like green sulfur bacteria or purple bacteria. These kinds of bacteria are common in many aquatic habitats.
As the name suggests, anoxygenic photosynthesis doesn't generate oxygen. However, the byproduct of this type of photosynthesis process relies upon its electron donor.
FAQs on What Is Photosynthesis?
1. What is the basic definition of photosynthesis?
Photosynthesis is a vital anabolic process used by plants, algae, and some bacteria to convert light energy into chemical energy. During this process, these organisms, known as autotrophs, use sunlight, water, and carbon dioxide to create glucose (sugar), which serves as their food, and release oxygen as a byproduct. It is the primary way energy enters most ecosystems on Earth.
2. What are the essential requirements for photosynthesis to occur?
There are four main components essential for photosynthesis:
Sunlight: Provides the energy to drive the chemical reactions.
Chlorophyll: The green pigment found in chloroplasts that absorbs light energy.
Carbon Dioxide (CO₂): Taken from the atmosphere through small pores in the leaves called stomata, it provides the carbon atoms to build glucose.
Water (H₂O): Absorbed from the soil through the roots, it provides the electrons and protons needed for the reactions and is the source of the released oxygen.
3. What is the balanced chemical equation for photosynthesis?
The overall balanced chemical equation for photosynthesis is:
6CO₂ + 6H₂O + Light Energy → C₆H₁₂O₆ + 6O₂
This equation shows that six molecules of carbon dioxide and six molecules of water, using light energy, are converted into one molecule of glucose (a six-carbon sugar) and six molecules of oxygen.
4. Where in a plant does photosynthesis primarily take place?
Photosynthesis primarily occurs in the leaves of a plant. Within the leaf cells, the process is specifically located inside organelles called chloroplasts. The chloroplast has two main sites for the different stages of photosynthesis: the thylakoid membranes (where the light-dependent reactions happen) and the stroma (the fluid-filled space where the light-independent reactions, or Calvin cycle, occur).
5. Which organisms besides green plants can perform photosynthesis?
While plants are the most well-known, several other organisms are capable of photosynthesis. These include:
Algae: Eukaryotic organisms, ranging from single-celled phytoplankton to large seaweeds, that contain chlorophyll.
Cyanobacteria: These are prokaryotic organisms, also known as blue-green algae, that were among the first life forms to perform oxygenic photosynthesis.
Some Protists: Organisms like euglena have chloroplasts and can photosynthesise.
6. How do the light-dependent and light-independent reactions of photosynthesis differ?
The two stages of photosynthesis have distinct roles and locations. The light-dependent reactions directly require sunlight, occur in the thylakoid membranes, and use water to produce ATP and NADPH (energy-carrying molecules) while releasing oxygen. In contrast, the light-independent reactions (Calvin Cycle) do not directly need light, occur in the stroma, and use the ATP and NADPH from the light reactions to convert carbon dioxide into glucose.
7. Why is photosynthesis considered one of the most important biological processes on Earth?
The importance of photosynthesis is twofold. First, it is the foundation of nearly all food chains, as it produces the organic compounds (food) that sustain almost all life on the planet. Second, it is responsible for producing the oxygen in our atmosphere, which is essential for the survival of aerobic organisms, including humans, who rely on it for cellular respiration.
8. Is there a difference between photosynthesis and respiration in plants?
Yes, they are essentially opposite processes. Photosynthesis is an anabolic process that builds glucose to store energy, consumes CO₂, and releases O₂. It only occurs in cells with chlorophyll and in the presence of light. Respiration is a catabolic process that breaks down glucose to release energy for the plant's life functions, consumes O₂, and releases CO₂. Respiration occurs continuously in all living cells of the plant, day and night.
9. What are the major factors that can affect the rate of photosynthesis?
The rate of photosynthesis is influenced by several external and internal factors, often called limiting factors. The main ones include:
Light Intensity: The rate increases with light intensity up to a saturation point.
Carbon Dioxide Concentration: Higher CO₂ concentration increases the rate, again, up to a certain limit.
Temperature: Photosynthesis has an optimal temperature range. If it is too cold or too hot, the enzymes involved can become inactive or denatured, slowing the rate.
Water Availability: A shortage of water can cause the stomata to close, which limits the intake of CO₂.
