How Does Photosynthesis Work in Plants?
How Does Photosynthesis Work in Plants?
Chloroplasts play a key role in the process of photosynthesis. Learn about photosynthesis's light reaction in the grana and thylakoid membrane and dark reaction in the stroma.
Encyclopædia Britannica, Inc.
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Encyclopædia Britannica, Inc.Chloroplasts play a key role in the process of photosynthesis. Learn about photosynthesis's light reaction in the grana and thylakoid membrane and dark reaction in the stroma.
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Encyclopædia Britannica, Inc.An explanation of how structures inside the leaf contribute to plant coloration.
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Encyclopædia Britannica, Inc.The location, importance, and mechanisms of photosynthesis. Study the roles of chloroplasts, chlorophyll, grana, thylakoid membranes, and stroma in photosynthesis.
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Contunico © ZDF Studios GmbH, Mainz; Thumbnail © Citalliance/Dreamstime.comLearn why leaves of deciduous trees change colour in autumn.
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© MinuteEarth (A Britannica Publishing Partner)The perfect absorbers of solar radiation are black objects, yet plants, which depend on efficient mechanisms of absorbing solar radiation, are overwhelmingly green. Speculation of why this is so ranges from random chance to the possibility that the radiation-absorbing properties of chlorophyll are adequate to provide for the energy needs of Earth's plants.
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© MinuteEarth (A Britannica Publishing Partner)Molecules of chlorophyll, the key photosynthetic pigment in green plants, are arranged within a leaf such that they minimize the plant's need to transport incoming solar radiation while also increasing a leaf's photosynthetic output.
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Encyclopædia Britannica, Inc.Cellular respiration releases stored energy in glucose molecules and converts it into a form of energy that can be used by cells.
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Encyclopædia Britannica, Inc.Learn about the process of photosynthesis.
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Encyclopædia Britannica, Inc.All living things are composed of cells.
Transcript
NARRATOR: The most important parts of any plant are those that support photosynthesis. Photosynthesis requires special enzymes and pigments found in green plant tissues exposed to the sun. If a cell is woody or from a root, it will not have a chloroplast.
A plant cell capable of photosynthesis will have at least one chloroplast but may have 100 or more. Chloroplasts carry their own DNA and are able to reproduce on their own. Because of this, scientists speculate whether chloroplasts were once living organisms—possibly even parasites—independent of the plants that bear them today.
Chloroplasts are surrounded by a double membrane, which encloses even tinier membranes where photosynthesis takes place. These small membranes are folded into disk-shaped structures known as thylakoids, which are arranged in stacks called grana. The grana are surrounded by stroma, a semifluid matrix that contains proteins and other material to support the grana.
Photosynthesis happens in two steps. In the first step, the light reaction, chlorophyll in the grana absorbs light. The light's energy is transferred through a series of enzymes in the thylakoid membrane, resulting in the production of two energy-carrying compounds: ATP and NADPH. During this process, water molecules are split and oxygen is given off as a waste material.
The second step, the dark reaction, occurs in the stroma. The energy stored in NADPH and ATP powers a reaction that uses carbon dioxide and water to produce the sugar glucose. Glucose serves as a source of food for the plant.
Plants in turn serve as a source of food for animals, which cannot capture energy from the sun as plants do. This explains why plants are so essential to life on Earth.
A plant cell capable of photosynthesis will have at least one chloroplast but may have 100 or more. Chloroplasts carry their own DNA and are able to reproduce on their own. Because of this, scientists speculate whether chloroplasts were once living organisms—possibly even parasites—independent of the plants that bear them today.
Chloroplasts are surrounded by a double membrane, which encloses even tinier membranes where photosynthesis takes place. These small membranes are folded into disk-shaped structures known as thylakoids, which are arranged in stacks called grana. The grana are surrounded by stroma, a semifluid matrix that contains proteins and other material to support the grana.
Photosynthesis happens in two steps. In the first step, the light reaction, chlorophyll in the grana absorbs light. The light's energy is transferred through a series of enzymes in the thylakoid membrane, resulting in the production of two energy-carrying compounds: ATP and NADPH. During this process, water molecules are split and oxygen is given off as a waste material.
The second step, the dark reaction, occurs in the stroma. The energy stored in NADPH and ATP powers a reaction that uses carbon dioxide and water to produce the sugar glucose. Glucose serves as a source of food for the plant.
Plants in turn serve as a source of food for animals, which cannot capture energy from the sun as plants do. This explains why plants are so essential to life on Earth.