Photosynthesis Process

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Unlike animals, most plants do not need to find food, because they can make it for themselves. Plants use energy from sunlight to turn water and carbon dioxide into an energy-rich sugar called glucose. This process is called photosynthesis, which means “making things with light”. Photosynthesis takes place inside capsules in the leaf cells, called CHLOROPLASTS.

Photosynthesis is a process in which green plants use energy from the sun to transform water, carbon dioxide, and minerals into oxygen and organic compounds. It is one example of how people and plants are dependent on each other in sustaining life.

Photosynthesis happens when water is absorbed by the roots of green plants and is carried to the leaves by the xylem, and carbon dioxide is obtained from air that enters the leaves through the stomata and diffuses to the cells containing chlorophyll. The green pigment chlorophyll is uniquely capable of converting the active energy of light into a latent form that can be stored (in food) and used when needed.

Photosynthesis provides us with most of the oxygen we need in order to breathe. We, in turn, exhale the carbon dioxide needed by plants. Plants are also crucial to human life because we rely on them as a source of food for ourselves and for the animals that we eat.


Making Food & Oxygen

Plants use their leaves to make food. Oxygen is created as a by-product. During photosynthesis, plant leaves take in carbon dioxide from the atmosphere. Using the energy from sunlight, this is combined with water drawn up from the roots to make glucose. Oxygen is also produced in this chemical reaction and exits the leaves into the surrounding air.

Food Producing Cells

 Different plant cells perform different tasks. Palisade cells and spongy cells are located just below the epidermis and are a plant’s main food-producers. The tall palisade cells are packed with green chloroplasts, which carry out photosynthesis. The irregularly shaped spongy cells also have chloroplasts. Air spaces between the cells are filled with carbon dioxide, water vapour and other gases.

Chloroplast

Many leaf cells contain tiny, lens-shaped organelles called chloroplasts. These can move around the cell towards the direction of sunlight. Chloroplasts contain a green, light-capturing pigment called chlorophyll. This chemical helps the chloroplasts to act like minute solar panels.
    • Chloroplasts are made up of stacks of tiny disclike membranes called grana, held in a dense mass of material known as the stroma. The grana are where water is split into hydrogen and oxygen, using some of the light energy captured by the chlorophyll. The rest of the light energy is used in the stroma to combine the hydrogen with the carbon dioxide to make

Photosynthesis Process

The initial process in photosynthesis is the decomposition of water (H2O) into oxygen, which is released, and hydrogen; direct light is required for this process. The hydrogen and the carbon and oxygen of carbon dioxide (CO2) are then converted into a series of increasingly complex compounds that result finally in a stable organic compound, glucose (C6H12O6), and water. This phase of photosynthesis utilizes stored energy and therefore can proceed in the dark. The simplified equation used to represent this overall process is 6CO2+12H2O+energy= C6H12O6+6O2+6H2O. In general, the results of this process are the reverse of those in respiration, in which carbohydrates are oxidized to release energy, with the production of carbon dioxide and water.

The intermediary reactions before glucose is formed involve several enzymes, which react with the coenzyme ATP (see adenosine triphosphate) to produce various molecules. Studies using radioactive carbon have indicated that among the intermediate products are three-carbon molecules from which acids and amino acids, as well as glucose, are derived. This suggests that fats and proteins are also products of photosynthesis. The main product, glucose, is the fundamental building block of carbohydrates (e.g., sugars, starches, and cellulose). The water-soluble sugars (e.g., sucrose and maltose) are used for immediate energy. The insoluble starches are stored as tiny granules in various parts of the plant—chiefly the leaves, roots (including tubers), and fruits—and can be broken down again when energy is needed. Cellulose is used to build the rigid cell walls that are the principal supporting structure of plants.

 Importance of Photosynthesis Animals and plants both synthesize fats and proteins from carbohydrates; thus glucose is a basic energy source for all living organisms. The oxygen released (with water vapor, in transpiration) as a photosynthetic byproduct, principally of phytoplankton, provides most of the atmospheric oxygen vital to respiration in plants and animals, and animals in turn produce carbon dioxide necessary to plants. Photosynthesis can therefore be considered the ultimate source of life for nearly all plants and animals by providing the source of energy that drives all their metabolic processes.

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