Sugar has been valued as a commodity for thousands of years. Despite its long history in commerce, the biological mechanisms accounting for the production of sugar are rather recent discoveries. The reactions are remarkable. Sugar is produced by all green plants and photosynthetic bacteria in a reaction sequence capable of forming carbon-carbon bonds.
The very first steps occur independently of solar energy input, but to sustain the reaction, the products of initial fixation are phosphorylated and undergo a reduction in oxidation state. 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. 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. 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 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.
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. 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 a sugar called glucose.
Involves producing a four-carbon intermediate compound, which splits into carbon dioxide and a three-carbon compound during the Calvin Cycle in plants that do not get a lot of light or water. In a plant cell, the protein-containing matrix between the thylakoid membranes and the chloroplast membrane. 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. Tyson Brown, National Geographic Society. For example, fructose, or fruit sugar, shares a structure similar to glucose, but it is used in different parts of the plant. As simple sugars are water soluble, plants can access and use them easily. Glucose appears in the stems of some plants, like the corn plant, while fructose, as its name implies, appears commonly in fruit.
Humans and other animals often eat these foods to gain these basic units of chemical energy. Starch acts as a form of reserve energy in plants. Plants contain two types of starch — amylose and amylopectin — both polysaccharides or combinations of sugar molecules. In some cases, it takes thousands of sugar molecules to form a starch. Roots, legumes and seeds commonly contain starches, the latter case because starch feeds the embryonic stage of a plant. Animals use their digestive enzymes to break down starches into simple sugars for use.
Foods like potatoes contain high levels of the sugar chains.
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