what is photosynthesis in biology? In science

Photosynthesis is a process in which the light energy of energy-depleting inorganic oxide compounds reduces carbon (CO2) and hydrogen (water) to energy-rich carbohydrates (sugar and glucose). Chlorophyll and photosynthesis pigments convert light energy into the chemistry that can. The next process occurs in photosynthesis.

Photosynthesis formula 1

Photosynthetic Reactants and Products

Carbon dioxide (CO2), water, and light are reactive materials for photosynthesis, while glucose and oxygen are the products of photosynthesis. Water used as a reactor in some reactions and is released as a product in other reactions. So water appears on either side of the equation. Since there is no net production for H2O, the equation can be simplified as follows:

Photosynthesis formula 2

This is the exact opposite of the air-breathing equation. Photosynthesis uses breathing products, while respiration uses photosynthesis products.

Reactions of Photosynthesis

Photosynthesis is the process of reduction. Its represented by the following simplified equation.

Photosynthesis formula 3

However, this is not an easy step. This is a complex process. This can accomplished through a series of simple steps or reactions. The light reaction continues in two steps.

1.Light-dependent reactions (light reactions)
Light used directly. Chlorophyll and other optical dye molecules absorb light energy. These dyes should reduced and absorbed. They convert light energy into chemical energy. As a result of this energy transformation, NADPH2 (NADPH + H +) and ATP molecules formed. ATP is a temporary energy storage complex. Stored Energy and H+ used for non-light interactions.

2.Independent light reaction (dark reaction)
It does not directly use light energy. NADPH2 provides electrons (and H +) in a dark reaction, while ATP provides energy. It reduces carbon dioxide to form sugar. This stage of photosynthesis also called a dark reaction because it does not directly use light energy. This stage can well occur in dark and dark. It only requires a mild reaction from NADPH2 and ATP.

Water and Photosynthesis

The oxygen released during photosynthesis comes from the water. It is an important source of oxygen in the atmosphere. Most organisms need this oxygen to breathe and collect energy.

The hypothesis of Van Neil

A hypothesis suggested that plants spray water. Water is the source of hydrogen. It releases oxygen as a byproduct. He made assumptions based on photosynthesis experiments in bacteria. These bacteria produce carbohydrates from carbon dioxide. But they will not release oxygen.

Confirmation of Neil’s hypothesis


According to Neil’s assumption, water is the source of oxygen, not carbon dioxide. This assumption later confirmed in the 1940s. Isotope trackers used in biological research. Water and carbon dioxide containing the heavy oxygen tope 18 prepared in the laboratory. Two groups of green plants formed.

  • A group of plants given CO2 containing 018 of H20 and O2 containing normal oxygen.
  • The second group of plants given H20 containing normal oxygen and CO2 containing O18.

It was found that the first group of plants produced 18, but the second group of plants did not produce O18.

Group -1 Plants:

Photosynthesis formula 4

Group -2 Plants:

Photosynthesis formula 5

Therefore, water is one of the raw materials for photosynthesis. Other raw materials are carbon dioxide. Hydrogen produced by hydrolysis. NADP + (nicotinamide dinucleotide phosphate) reduced to NADPH + H +. NADPH2 has reduced power. Itsformed with ATP during photosynthesis of photosynthesis. NADPH + can reduce carbon dioxide to form sugar during a dark reaction.

Chloroplasts – The Sites of Photosynthesis in plants

All green parts of the plant contain chloroplasts. But the leaves are the main site for photosynthesis in most plants. The number of chloroplasts is very large. There are approximately one million chloroplasts per square millimeter of the leaf surface. Green chloroplasts mainly found in the cells of leaf tissues. Each mesophyll contains around 20-100 chloroplasts.

Structure of Chloroplast

The chloroplast contains a double film. Surrounds a thick liquid inside called a matrix. This matrix contains most of the photosynthetic enzymes. Another membrane system suspended in the matrix. These membranes called thylakoids. A thylakoid a group of flat, tablet-shaped capsules that attached to each other.

Inside thylakoid, there is a space or a thylakoid cavity filled with fluid. Itsseparated from the matrix by the thylakoid membrane. Thylakoid membranes stacked in rows in certain places. The stacked column of these thylakoids called Grana (one particle).

Chlorophyll and other photosynthesis pigments included in the thylakoid membrane. Chlorophyll turns green plants. The electronic receivers of the photoelectron transport chain are part of these membranes. Therefore, the thylakoid membrane involved in the synthesis of ATP through chemical penetration.

Chlorophyll and other pigments absorb light energy. This light energy converted into chemical energy in the form of ATP and NADPH. These products used to collect sugar in the chloroplast matrix of green.

Green chloroplasts not found in prokaryotes. Instead, they do have stacked light films. These membranes act like thylakoids.

Photosynthetic Pigments

Green chloroplasts contain pigments that absorb light. Tinctures are materials that absorb visible light (wavelength 380-750 nm). Different pigments absorb light from different wavelengths (colors). The wavelength absorbed by the pigment disappears.

A tool called an optical spectrometer used to measure the relative ability of different pigments to absorb different light. “A pigment that absorbs light at different wavelengths called the absorption spectrum of the pigment.”

Thylakoid membranes contain different types of pigments. Chlorophyll is the main optical pigment. There are other auxiliary pigments in chloroplasts. and this is:

  • Carotenoids: These have yellow and red-orange to color.
  • Carotenes: They have red to or color.
  • Xanthophylls: they have a yellow color.


Chlorophyll is a green dye. Its found in all light creatures. It is insoluble in water but soluble in organic solvents, such as carbon tetrachloride (CCl4), alcohol, etc.

Types of chlorophyll

There are many types of chlorophyll. They are chlorophyll a, b, c, d, e. These dyes found in eukaryotic plants. Its found in photosynthetic bacteria called bacterial chlorophyll.

Chlorophyll absorption wavelength

Chlorophyll mainly absorbs the wavelengths of blue, purple, and orange-red. Its absorbs at least the green and yellow wavelengths. Therefore, these wavelengths transmitted or reversed. Dark green always persuades yellow. Therefore, the plant appears green. Unless other pigments cover it, it will remain green.

The structure of chlorophyll

The chlorophyll molecule consists of two main parts:

Hydrophilic Head

They are flat, square, and light-absorbing parts. The head contains a complex porphyrin ring. The ring consists of four smaller continuous units (called the Phytol rings). Each ring of Phytol consists of carbon and nitrogen atoms. Magnesium atoms are in the center of the porphyrin ring.

The Mg atom coordinated with nitrogen for each pyrrole ring. This is why magnesium deficiency can make plants yellow. The Haem group of hemoglobin is also a porphyrin ring. But its center is an iron atom, not magnesium.

Hydrophobic hydrocarbon tail

It is a long and anchored part. It consists of a long hydrocarbon chain called Vitol (C20OH39). Plant alcohol associated with one of the Phytol rings. The chlorophyll molecules embedded in the hydrophobic heart of the thylakoid membrane through this tail.

Carotenoids, Accessory Pigments

Carotenoids are yellow, red to orange pigments. They strongly absorb wavelengths in the blue-violet range. Therefore, they absorb different wavelengths than chlorophyll. In this way, the spectrum of the absorbed light increased. Therefore, it provides more energy for photosynthesis.

Carotenoids and chlorophyll B absorb light and transfer energy to chlorophyll a. Then the chlorophyll begins a light reaction. Therefore, carotenoids and chlorophyll called auxiliary pigments (A). The power transmission sequence is as follows:

Photosynthesis formula 6

Some carotenoids protect chlorophyll from strong light. It absorbs and dissipates a lot of light energy and does not transfer this energy to chlorophyll. Similar carotenoids can protect the human eye.

Light-driven energy

Light is a form of energy. This called energy or electromagnetic radiation. Light appears as waves and particles. Light particles called photons. Visible light radiation of 380 to 750 nanometers in length is vital to life.

Chlorophyll absorbs the energy of sunlight. Converts this energy into chemical energy during photosynthesis. Chlorophyll cannot absorb all the light falling on its surface. The leaf surface absorbs only one percent of light energy. The remaining light reflected or transmitted.

Absorption spectrum

“The graph (graph) showing the absorption of light by vehicles at different wavelengths called the absorption spectrum.” It shows that absorption is the maximum in the blue and red parts of the spectrum.

Blue and red absorption peaks are 430 nm and 670 nm wavelengths, respectively. The peaks of carotenoid absorption contain different forms of chlorophyll.

Action spectrum

“The graph (graph) that shows the relative effectiveness of different wavelengths (colors) of photosynthesis called the working spectrum.” The first work spectrum obtained by the German biologist TW. In 1883 Engelmann (Engelmann). He involved in spirulina research. Different pigments absorb different wavelengths.

The effect of different wavelengths also differs in different dyes. The spectrum of action can measured in a simple way. Light the plants with light at different wavelengths (colors). Estimating the relative amount of spent carbon dioxide or oxygen released during photosynthesis at every wavelength. The working spectrum indicates that chlorophyll is a light pigment.

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