Energy and Life
• Plants and some other type of organisms are able to use light energy from the sun to produce food.
• Organisms such as plants, which make their own food, are called autotrophs.
• Other organisms, such as animals, cannot use the sun’s energy directly, these are known as heterotrophs. They obtain energy from the foods they consume.
• One of the principal chemical compounds that living things use to store energy is adenosine triphosphate (ATP).
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• The energy released when ATP is released when ATP is converted into ADP and a phosphate group.
• The characteristics of ATP make it an exceptionally useful molecule that is used by all types of cells as their basic energy source.
• ATP also powers movement within the cell. Cell organelles are moved long microtubules by motor proteins that use the energy of ATP to generate force.
• A single molecule if the sugar glucose stores more than 90 times the chemical energy of a molecule of ATP.
• In the process of photosynthesis, plants use the energy of sunlight to convert water and carbon dioxide into oxygen and high-energy carbohydrates – sugars and starches.
• In the 1600s, the Belgian physician Jan van Helmont devised an experiment to find out if plants grew by taking material out of the soil.
• Many scientists have contributed to understanding how plants carry out photosynthesis. Early research focused on the overall process. Later researchers investigated the detailed chemical pathways.
• The experiments performed by van Helmont, Priestley, Ingenhouz, and other scientists reveal that in the presence of light, plants transform carbon dioxide and water into carbohydrates and release oxygen.
• Photosynthesis is a series of reactions that uses energy from the sun to convert water and carbon dioxide into sugars and oxygen. Photosynthesis takes place in a plant organelle called the chloroplast.
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• Photosynthesis uses the energy of sunlight to convert water and carbon dioxide into oxygen and high-energy sugars.
• Plants then use the sugars to produce complex carbohydrates such as starches. Plants obtain carbon dioxide from the air or water in which they grow.
• In addition to water and carbon dioxide, photosynthesis requires light and chlorophyll, a molecule in charge of chloroplasts.
• Plants gather the sun’s energy with light absorbing molecules called pigments. The plants’ principal pigment is chlorophyll.
• In plants and other photosynthetic eukaryotes, photosynthesis takes place inside chloroplasts.
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• The chloroplasts contain saclike photosynthetic membranes called thylakoids. Thylakoids are arranged in stacks known as grana. Thylakoids contain clusters of chlorophyll and other pigments and protein known as photosystems that are able to capture the energy of sunlight.
• The stroma is the region outside the thylakoid membranes.
• Light Dependent Reactions: Take place in the thylakoids, and takes water, and uses the sun’s energy to make ATP and NADPH. Also gives off oxygen.
• NADPH: Carries high energy electrons. NADP^+ + H  NADPH.
• Light Independent – Uses ATP and NADPH to turn carbon dioxide into glucose.