C4: Solar Energy
Photosynthesis is the process by which sunlight is converted to chemical energy. Sunlight is absorbed into chloroplasts by the chemical chlorophyll. Visible light can be absorbed by molecules that have a conjugated structure with an extended system of alternating single and multiple bonds. When light is absorbed, electrons get excited and jump to higher energy levels within the visible wavelength region. When the electrons calm down, they jump back to lower energy levels and emit a photon of light in a particular color or wavelength. During photosynthesis, the return of the electron to the ground state takes place during a complex series of chemical reactions.
Pigments in plants are colored due to conjugated double bond systems. If a certain pigment absorbs red and green and/or yellow light as a result of its conjugation, then blue or purple light will be reflected. Chlorophyll absorbs red and blue light, but reflects green.
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Pigments in plants are colored due to conjugated double bond systems. If a certain pigment absorbs red and green and/or yellow light as a result of its conjugation, then blue or purple light will be reflected. Chlorophyll absorbs red and blue light, but reflects green.
Image courtesy of biologyexams4u.com.
The conversion of carbon dioxide to carbohydrates using solar energy by photosynthesis produces our food and fuels. Biofuels such as ethanol are obtained from corn sugar or glucose by fermentation. See the equation on page 676. The ethanol produced in this manner can be blended with gasoline. Biodiesel is another sustainable fuel that can be grown and used as a diesel substitute. It is produced from vegetable oils, which can release similar amounts of energy to diesel when burned. However, it is viscous and therefore, unable to flow easily. This can be overcome by converting the vegetable oils to a less viscous ester with fewer intermolecular forces. See the transesterification process on page 676.
In this process to form biodiesel, the vegetable oil is typically heated with a sodium or potassium hydroxide catalyst along with methanol to produce the methyl ester, or ethanol to produce the ethyl ester of the triglyceride.
Page 677 provides a list of the advantages and disadvantages of biodiesel. My understanding is that you need to know these for the exam.
In this process to form biodiesel, the vegetable oil is typically heated with a sodium or potassium hydroxide catalyst along with methanol to produce the methyl ester, or ethanol to produce the ethyl ester of the triglyceride.
Page 677 provides a list of the advantages and disadvantages of biodiesel. My understanding is that you need to know these for the exam.